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Aleklett, Kristin Anna Eva. "Examining ecological determinants of community formation and stability in the root microbiota." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/56741.
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The root system of a plant is known to host a wide diversity of microbes that can be beneficial or detrimental to the plant. Microbial ecologists have long struggled to understand the factors influencing the composition of these communities. One overlooked aspect of microbial community assembly in root systems is the potential for individual variation among plants, and the potential effect of early colonisation events such as microbial exposure of the seed inside the parent plant and during dispersal.
In this dissertation, I relate ecological theory of community assembly to the formation of the root microbiota. I explore the extent of variation between individuals in wild plant populations, and examine the effects of historical contingency in determining bacterial and fungal community assembly and stability in the root microbiota.
The main findings in my work showed that:
- Wild plants growing in close proximity, sharing environmental conditions will still host distinct bacterial communities in their root systems based on their species identity. We also documented individual variation in root microbiota within all species examined, even the clonal plant species Pilosella aurantiaca.
- Bacterial community composition varies significantly across the body of a plant, with different parts of the plant body hosting distinct communities.
- Plants are able to form new microbial associations throughout development, but the timing of microbial exposure affects the composition of the microbial community in mature plants.
- Microbial community stability fluctuates within weeks during early plant development, with one week-old plants hosting communities most likely to change in composition.Irving K. Barber School of Arts and Sciences (Okanagan)
Biology, Department of (Okanagan)
Graduate
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Yamashita, José Carlos. "Avaliação da microbiota e da reparação apical e periapical após preparo biomecânico de canais radiculares com diferentes soluções irrigadoras, em dentes de cães com reação periapical crônica /." Araraquara : [s.n.], 2004. http://hdl.handle.net/11449/101639.
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Orientador: Mário Tanomaru FilhoBanca: Mario Roberto Leonardo
Banca: Léa Assed Bezerra da Silva
Banca: Igor Prokopowitsch
Banca: Francisco José de Souza Filho
Resumo: O objetivo deste estudo foi avaliar a microbiota presente no sistema canais radiculares antes e após o preparo biomecânico; e as condições histopatológicas da reparação apical e periapical após preparo biomecânico dos canais radiculares de dentes com reação periapical crônica. Foram utilizados 78 canais radiculares de dentes de cães, os quais, após indução de lesão periapical, foram submetidos ao preparo biomecânico utilizando as seguintes soluções irrigadoras: solução de digluconato de clorexidina a 2%, de hipoclorito de sódio a 2,5% ou soro fisiológico. Um grupo controle não recebeu preparo biomecânico. Foram realizadas culturas microbiológicas antes e após 30 dias do preparo biomecânico. Após este período os animais foram mortos para processamento e análise histopatológica. O estudo microbiológico demonstrou que houve redução dos microrganismos nos grupos que utilizaram soluções antimicrobianas (p<0,05), com melhor resultado para a solução de clorexidina. Os grupos que utilizaram solução fisiológica controle apresentaram aumento de microrganismos. No estudo histopatológico, foi observado, de um modo geral, infiltrado inflamatório periapical severo e em grande extensão, severo espessamento do ligamento periodontal e grandes áreas de reabsorção óssea e apical em todos os grupos (p>0,05). Concluiu-se que o emprego de soluções irrigadoras antimicrobianas durante o preparo biomecânico promove redução da microbiota endodôntica, sem a sua eliminação do sistema de canais radiculares em dentes de cães com lesão periapical. A solução de clorexidina a 2% proporcionou maior redução da microbiota que a solução de hipoclorito de sódio a 2,5% (p<0,05). Porém, os resultados histopatológicos demonstram que somente o preparo biomecânico não foi capaz de criar condições para reparação dos tecidos apicais e periapicais.
Abstract: The aim of this study was to evaluate the microorganisms in the root canal system before and after biomechanical preparation and the apical and periapical repair after this biomechanical preparation. The study was performed in 78 root canals of dog's teeth with induced chronic periradicular lesion. There were used the following endodontic irrigating solutions: 2% chlorhexidine digluconate solution; 2.5% sodium hypochlorite solution, saline solution and a control group without biomechanical preparation. The microbiological sampling were performed before and 30 days after the biomechanical preparation. After this period the animals were killed to histological analysis. In the microbiologic study, the results showed that the antimicrobial solutions used reduced the number of microorganisms (p<0.05). The chlorhexidine solution showed better performance. The group that used saline solution and the control group presented an increased number of microorganisms. The histological results showed a severe periapical inflammation, severe thickness of periodontal ligament, apical and osseous resorption in all groups (p>0.05). It was concluded that the antimicrobial endodontic solution reduced but not eliminated the microorganisms present in root canals of dogþs teeth with necrosis and periapical lesion. The chlorhexidine solution was more effective in reducing the number of microorganisms than sodium hypochlorite solution (p<0.05). Although, the histopathological results showed that the biomechanical preparation alone was not capable to promote an adequate condition for the apical and periapical tissues repair.
Doutor
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Yamashita, José Carlos [UNESP]. "Avaliação da microbiota e da reparação apical e periapical após preparo biomecânico de canais radiculares com diferentes soluções irrigadoras, em dentes de cães com reação periapical crônica." Universidade Estadual Paulista (UNESP), 2004. http://hdl.handle.net/11449/101639.
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yamashita_jc_dr_arafo.pdf: 1654679 bytes, checksum: ea4cab55ba1e8890848c0a5afe9fc1d2 (MD5)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O objetivo deste estudo foi avaliar a microbiota presente no sistema canais radiculares antes e após o preparo biomecânico; e as condições histopatológicas da reparação apical e periapical após preparo biomecânico dos canais radiculares de dentes com reação periapical crônica. Foram utilizados 78 canais radiculares de dentes de cães, os quais, após indução de lesão periapical, foram submetidos ao preparo biomecânico utilizando as seguintes soluções irrigadoras: solução de digluconato de clorexidina a 2%, de hipoclorito de sódio a 2,5% ou soro fisiológico. Um grupo controle não recebeu preparo biomecânico. Foram realizadas culturas microbiológicas antes e após 30 dias do preparo biomecânico. Após este período os animais foram mortos para processamento e análise histopatológica. O estudo microbiológico demonstrou que houve redução dos microrganismos nos grupos que utilizaram soluções antimicrobianas (p<0,05), com melhor resultado para a solução de clorexidina. Os grupos que utilizaram solução fisiológica controle apresentaram aumento de microrganismos. No estudo histopatológico, foi observado, de um modo geral, infiltrado inflamatório periapical severo e em grande extensão, severo espessamento do ligamento periodontal e grandes áreas de reabsorção óssea e apical em todos os grupos (p>0,05). Concluiu-se que o emprego de soluções irrigadoras antimicrobianas durante o preparo biomecânico promove redução da microbiota endodôntica, sem a sua eliminação do sistema de canais radiculares em dentes de cães com lesão periapical. A solução de clorexidina a 2% proporcionou maior redução da microbiota que a solução de hipoclorito de sódio a 2,5% (p<0,05). Porém, os resultados histopatológicos demonstram que somente o preparo biomecânico não foi capaz de criar condições para reparação dos tecidos apicais e periapicais.
The aim of this study was to evaluate the microorganisms in the root canal system before and after biomechanical preparation and the apical and periapical repair after this biomechanical preparation. The study was performed in 78 root canals of dog's teeth with induced chronic periradicular lesion. There were used the following endodontic irrigating solutions: 2% chlorhexidine digluconate solution; 2.5% sodium hypochlorite solution, saline solution and a control group without biomechanical preparation. The microbiological sampling were performed before and 30 days after the biomechanical preparation. After this period the animals were killed to histological analysis. In the microbiologic study, the results showed that the antimicrobial solutions used reduced the number of microorganisms (p<0.05). The chlorhexidine solution showed better performance. The group that used saline solution and the control group presented an increased number of microorganisms. The histological results showed a severe periapical inflammation, severe thickness of periodontal ligament, apical and osseous resorption in all groups (p>0.05). It was concluded that the antimicrobial endodontic solution reduced but not eliminated the microorganisms present in root canals of dogþs teeth with necrosis and periapical lesion. The chlorhexidine solution was more effective in reducing the number of microorganisms than sodium hypochlorite solution (p<0.05). Although, the histopathological results showed that the biomechanical preparation alone was not capable to promote an adequate condition for the apical and periapical tissues repair.
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Hou, Shiji [Verfasser], Paul [Gutachter] Schulze-Lefert, and Ute [Gutachter] Höcker. "Root microbiota functions in mitigating abiotic and biotic stresses in Arabidopsis / Shiji Hou ; Gutachter: Paul Schulze-Lefert, Ute Höcker." Köln : Universitäts- und Stadtbibliothek Köln, 2021. http://d-nb.info/1231992778/34.
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Dombrowski, Nina [Verfasser], Paul [Akademischer Betreuer] Schulze-Lefert, Alga [Akademischer Betreuer] Zuccaro, and George [Akademischer Betreuer] Coupland. "Structural and functional analysis of the bacterial root microbiota of Arabidopsis thaliana and relative species / Nina Dombrowski. Gutachter: Paul Schulze-Lefert ; Alga Zuccaro ; George Coupland." Köln : Universitäts- und Stadtbibliothek Köln, 2015. http://d-nb.info/1071369857/34.
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Lopes, Lucas Dantas. "From communities to genomes: a multifaceted approach to depict bacterial life in soils." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-02012018-141554/.
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Unraveling soil microbial ecology is essential for improving sustainable agricultural productivity. Community-based studies revolutionized this field in the last decades, but much is yet to be disclosed. This thesis proposed an approach to increase the resolution of such studies by combining 16S rDNA high-throughput sequencing and population genomics, aiming to further explore the differences pointed by community analyses, as well as to overcome the limitations of using operational taxonomic units (OTUs) as ecological entities, and to introduce the evolutionary thinking in microbial ecology. Our main goal was to understand the features that make bacteria able to colonize sugarcane rhizosphere or live saprophytically in bulk soil. Rhizosphere and bulk soil are contrasting habitats for microbial life as they are highly distinct in its physical, chemical and consequently biological characteristics. Our results indicated that sugarcane shapes the rhizosphere microbiome and metabolism of D-galacturonic acid is a key function for colonizing this niche. Among the taxa prevailing in the rhizosphere, Pseudomonas genus was targeted for a more detailed study considering its known attributes for plant growth promotion. Seventy-six fluorescent Pseudomonas spp. were isolated and submitted to whole genome sequencing (WGS). A comparative genomic analysis was performed between populations from rhizosphere and bulk soil. Phylogenetic analyses classified the isolates in the P. fluorescens (57) or P. putida (19) groups. Twelve putative new species and two new proposed P. fluorescens subgroups were found in the prospected tropical soil. Comparative genomics revealed that phosphatases or xylose-utilization genes were significantly enriched in the rhizosphere and bulk soil populations of the P. fluorescens group, respectively. D-galactonate catabolism was higher in the rhizosphere population of the P. putida group based on both genotypic and phenotypic results. Growth in D-xylose was further explored using genetic modified strains and confirmed that this sugar is more used by members of the bulk soil than the rhizosphere population of the P. fluorescens group, a pattern also observed in the bulk soil microbiome. In summary, these findings constitute a step forward in understanding the ecology of rhizosphere and bulk soil bacteria, by overcoming some limitations of community-based analyses and showing genomic differences between bacterial populations of these habitats.Desvendar a ecologia microbiana do solo é essencial para aumentar a produtividade agrícola sustentável. Estudos baseados em comunidades revolucionaram esse campo nas últimas décadas, mas ainda há muito a ser revelado. Esta tese propôs uma abordagem para aumentar a resolução desses estudos, combinando sequenciamento em larga escala de rDNA 16S e genômica populacional, com o objetivo de explorar mais a fundo as diferenças apontadas por análises de comunidades, assim como superar as limitações do uso de unidades taxonômicas operacionais (UTOs) como entidades ecológicas e introduzir o pensamento evolutivo na ecologia microbiana. Nossa principal meta foi entender as características que tornam as bactérias hábeis em colonizar a rizosfera de cana-de-açúcar ou viver no solo saprofiticamente. Rizosfera e solo são hábitats contrastantes para a vida microbiana, já que são altamente distintos em suas características físicas, químicas e, consequentemente, biológicas. Nossos resultados indicaram que a cana-de-açúcar modifica o microbioma da rizosfera e o metabolismo do ácido D-galacturônico é uma função chave para colonizar este nicho. Dentre os táxons que prevalecem na rizosfera, o gênero Pseudomonas foi escolhido para um estudo mais detalhado, considerando os seus atributos de promoção de crescimento de plantas. Setenta e seis Pseudomonas spp. fluorescentes foram isoladas e submetidas ao sequenciamento do genoma. Uma análise de genômica comparativa foi realizada entre as populações obtidas do solo e rizosfera. As análises filogenéticas classificaram os isolados nos grupos P. fluorescens (57) ou P. putida (19). Doze prováveis novas espécies e dois novos subgrupos propostos de P. fluorescens foram encontrados no solo tropical prospectado. A genômica comparativa revelou que genes de fosfatases e de uso de xilose foram significativamente enriquecidos nas populações da rizosfera e solo do grupo P. fluorescens, respectivamente. O catabolismo do ácido D-galactônico foi maior na população da rizosfera do grupo P. putida, baseado tanto em resultados genotípicos quanto fenotípicos. O crescimento em D-xilose foi mais explorado usando linhagens geneticamente modificadas e confirmou que este açúcar é mais utilizado por membros da população do solo do que da rizosfera no grupo P. fluorescens, um padrão também observado no microbioma do solo. Em resumo, essas descobertas constituem um passo adiante no entendimento da ecologia bacteriana do solo e rizosfera, por superar algumas limitações de análises de comunidades e mostrar diferenças genômicas entre populações bacterianas destes hábitats.
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Achemedei, Bronwyn. "Potential risk factors associated with the microbiota of grass roots in the Kimberley region of Western Australia." Thesis, Achemedei, Bronwyn (2016) Potential risk factors associated with the microbiota of grass roots in the Kimberley region of Western Australia. Honours thesis, Murdoch University, 2016. https://researchrepository.murdoch.edu.au/id/eprint/35151/.
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The Kimberley region of Australia is a biological hotspot with highly diverse and often endemic flora and fauna. Much of the area has been understudied, although this has changed in recent years. The diversity of the microbiota of the region has remained relatively understudied, with the exception of a limited survey aimed at assessing the distribution of the pathogen Burkholderia pseudomallei. This study hypothesised that previously uncharacterised human pathogenic bacteria are present in the soils of the Kimberley region.
A total of 49 isolates were obtained from the rhizosphere, rhizoplane and bulk soil of 15 plant specimens. Of these, 18 isolates were identified as species that have been shown to cause disease in humans, and four isolates were selected to characterise further. The virulence of a Klebsiella pneumoniae, and three Burkholderia cepacia complex isolates were compared to clinical isolates. It was found that each isolate exhibited virulence factors, showing the ability to adhere to macrophage cells, form biofilms, and produce unique lipopolysaccharides. This study showed that the microbiota of the Kimberley region has the potential to cause disease in humans.
To further investigate the risk posed to the human population, these isolates should be studied further with improved virulence, and infection assays. Whole genome sequences should be analysed for the presence of specific virulence genes. The remaining uncharacterised isolates that have shown to be pathogenic in a clinical setting should be characterised further. Future studies should include a collection of more plant specimens, with more diversity in grass species collected, and from wider areas.
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Ourry, Morgane. "Contribution à l'analyse des interactions tripartites entre Brassica napus, Delia radicum et leur microbiote." Thesis, Rennes, Agrocampus Ouest, 2019. http://www.theses.fr/2019NSARA032.
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Les microorganismes exercent une forte influence sur les interactions plante-insecte. Nous avons étudié l’interaction entre le colza (Brassica napus), la mouche du chou (Delia radicum) et les communautés microbiennes qui leur sont associées. La diversité microbienne du sol a été manipulée par dilution jusqu’à extinction pour évaluer son effet sur la chimie de la plante et les traits d’histoire de vie de l’insecte. La différence de diversité a influencé le taux d’émergence et l’oviposition de la mouche, mais pas la chimie de la plante. A l’inverse, la phytophagie par D. radicum a drastiquement modifié la chimie des racines et les communautés microbiennes des racines et de la rhizosphère. Nous avons proposé le scénario selon lequel les plantes soumises à des attaques de phytophages produiraient des composes défensifs mais recruteraient aussi avec des composés chimiques attractifs, des microorganismes du sol qui permettraient à la plante de maintenir sesdéfenses. Les communautés bactériennes des mouches adultes, sans leur symbiote facultatif Wolbachia, ont été étudiées à l’aide d’un antibiotique. Nous avons montré que la tétracycline diminuait la diversité bactérienne des mouches sans les rendre stériles, modifiait la composition des communautés, et que les effets étaient durables sur plusieurs générations. Enfin, l’étude de la transmission des bactéries chez D. radicum a montré deux espèces partagées entre les femelles et les oeufs, et deux autres entre les larves et les racines et le sol. Cette étude montre qu’avoir une meilleure compréhension des interactions plantesinsecMicroorganisms have a strong influence on plant-insect interactions. We have studied the interaction between oilseed rape (Brassica napus), the cabbage root fly (Delia radicum) and their associated microbial communities. Soil microbial diversity was manipulated with the dilution to extinction approach to assess its effect on plant chemistry and insect life history traits. Diversity variation influenced the fly emergence rate and oviposition, but not plant chemistry. Conversely, herbivory by D. radicum strongly modified root chemistry and both root and rhizosphere microbial communities. We proposed a scenario that in the presence of herbivory, plants would produce defensive compounds but also would recruit, with attractive chemical compounds, soil microorganismsthat may maintain plant defenses. Bacterial communities of adult flies, free of their facultative symbiont Wolbachia, were studied using an antibiotic. We showed that tetracycline decreased fly bacterial diversity, without making them sterile, modified community composition, and that effect lasted over several generations. Lastly, studying bacterial transmission in D. radicum showed two species shared between females and eggs, and two others between larvae and both roots and rhizosphere. This study showed that having a better understanding of plant-insect interactions and how strongly microorganisms can influence their own host or other interacting organisms is a crucial step that could promote microbial applications in a context of insect biological control
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Lima, Bruna Roese de. "Detecção microbiana e de genes de resistência em ecossistemas da cavidade oral de pacientes infantis com necrose pulpar." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/128201.
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Alguns estudos caracterizaram a microbiota de canais radiculares de dentes decíduos com necrose pulpar como polimicrobiana, com predomínio de microrganismos anaeróbios. No entanto, nenhum estudo até o presente momento investigou a presença de genes de resistência a antimicrobianos em diferentes ecossistemas da cavidade oral de crianças. Este estudo tem por objetivo determinar a presença de espécies de Prevotella e do gene cfxa/cfxa2 associados à resistência à beta-lactâmicos, em diferentes ecossistemas orais de crianças com necrose pulpar. Vinte e sete crianças, que estavam sob cuidados odontológicos no Ambulatório de Clínica Infanto-Juvenil da Faculdade de Odontologia da UFRGS, e que apresentavam, pelo menos, um dente decíduo com necrose pulpar foram selecionados para este estudo. Foram coletadas amostras de saliva, biofilme supragengival, biofilme da câmara pulpar e do canal radicular de 32 dentes (27 posteriores e 5 anteriores). Após isolamento do DNA microbiano, a presença das bactérias Prevotella intermedia, Prevotella nigrescens, Prevotella tannerae e do gene cfxA/cfxA2 foi avaliada através do método de PCR. A amostra foi composta de pacientes com idade média de 5,5 anos (± 1,76). A taxa total de espécies de Prevotella foi de 29,1%, 25%, 21,8% e 32,29% em amostras de saliva, biofilme, câmara pulpar e canal radicular, respectivamente. As três espécies juntas não foram detectadas em todos os micro-ambientes do mesmo paciente, mas estavam presentes em 3,1% (n=1) de amostras do canal radicular. Prevotella nigrescens foi a bactéria mais frequentemente encontrada em todos os ecossistemas estudados. Foram observadas diferenças estatisticamente significativas em relação à presença de P. nigrescens em pelo menos um local e idade do paciente (teste t, p = 0,04). Também foi encontrada associação entre a presença desta bactéria, em pelo menos um local e uso de antimicrobianos (teste exato de Fisher, p = 0,014). A presença do gene de resistência à beta-lactâmicos, cfxA/cfxA2, foi testada em 12 pacientes da amostra, nos quatro micro-ambientes orais. Entre esses pacientes, 55,6% eram meninas, com idade média de 6 anos (± 2,5). Não foi detectada a presença deste gene em nenhuma amostra investigada. Os dados sugerem que a cavidade bucal de crianças com necrose pulpar apresenta presença diversificada de espécies de Prevotella em diferentes micro-ambientes orais. A ausência do gene cfxA/cfxA2 foi observada em todas as amostras investigadas. Estudos futuros, testando a presença de outros genes de resistência à beta-lactâmicos, são importantes para uma investigação abrangente.Some studies characterized the microbiota of root canals of primary teeth with pulp necrosis as polymicrobial, with a predominance of anaerobic microorganisms. However, no study to date has investigated the presence of antimicrobial resistance genes in different ecosystems of the oral cavity of children. This study aims to determine the presence of Prevotella species and genes associated with resistance to beta-lactams in different oral enviroments of children with pulp necrosis. Twenty-seven children who were under dental care at the Children and Youth Clinic (Dental School, UFRGS, Porto Alegre, Brazil), and who had at least one primary tooth with pulp necrosis were selected for this study. Saliva, supragingival biofilm, pulp chamber biofilm and root canal biofilm were collected of 32 teeth (27 posterior and 5 anterior). After isolation of microbial DNA, the presence of Prevotella intermedia, Prevotella nigrescens, Prevotella tannerae and cfxA/cfxA2 gene were evaluated using the PCR. The sample consisted of patients with a mean age of 5.5 years (± 1.76). The total rate of Prevotella species was 29.1%, 25%, 21.8% and 32.29% in saliva samples, biofilm, pulp chamber and root canal, respectively. The three strains were not detected in all enviroments of the same patient, but were present at 3.1% (n = 1) of the root canal samples. Prevotella nigrescens was the most common bacteria in all oral enviroments. Statistical significant differences were observed for the presence of P. nigrescens at least one oral enviroment and age of the patient (t-test, p = 0.04). Also an association was observed, among the presence of these bacteria in at least one enviroment and use of antimicrobials (Fisher's exact test, p = 0.014). The presence of the resistance gene to beta-lactams, cfxA/cfxA2, was tested on 12 patients of the sample at all four oral enviroments. Among these patients, 55.6% were girls with a mean age of 6 years (± 2.5). Absence of this gene in the sample investigated was detected. The absence of cfxA/cfxA2 gene was observed in all the investigated samples. Future studies testing the presence of other resistance genes to beta-lactams, are important for a comprehensive investigation.
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Pump, Judith [Verfasser], and Ralf [Akademischer Betreuer] Conrad. "Carbon translocation and methane emission in flooded rice microcosms with a manipulated root microbiome / Judith Pump. Betreuer: Ralf Conrad." Marburg : Philipps-Universität Marburg, 2013. http://d-nb.info/1035502224/34.
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Reis, Luciana Carvalho. "Capacidade de selamento de três materiais retrobturadores frente à infiltração microbiana por Enterococcus faecalis." Universidade do Estado do Rio de Janeiro, 2010. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=2650.
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O objetivo deste estudo foi comparar a capacidade de selamento apical de três materiais retrobturadores em dentes submetidos à infiltração microbiana por Enterococcus faecalis. Além de analisar a ocorrência da infiltração microbiana em relação à variável tempo. Para tal, foram utilizados 80 caninos superiores permanentes humanos extraídos, instrumentados com o sistema rotatório ProTaper Universal (MAILLEFER) e obturados pela técnica de compactação lateral, com dois tipos de cimento endodôntico: Endofill (DENTSPLY) e AH Plus (DENTSPLY). A apicetomia foi realizada com a remoção de 3mm do terço apical e o retropreparo confeccionado com pontas ultrasônicas. As amostras foram subdivididas, aleatoriamente, em 6 grupos com 10 dentes cada, e 2 grupos controles. Os materiais utilizados para a retrobturação foram MTA branco (ANGELUS), IBC BioAggregate (INNOVATIVE BIOCERAMIX INC.) e Acroseal (SEPTODONT). Foram confeccionados dispositivos para fixação dos dentes aos tubos Eppendorfs. As amostras foram inoculadas com cepas de E. faecalis e incubadas a 37C, por um período de 90 dias, para análise da presença de turvação do meio Enterococcosel. Para a realização da análise estatística foram utilizados os seguintes testes: Qui-quadrado com Prova Exata de Fisher e Kruskal-Wallis. Os resultados mostraram que todos os grupos nos quais foi realizada a obturação e a posterior retrobturação apresentaram infiltração. Comparando todos os grupos, não houve diferença significativa entre os materiais testados. Em relação apenas aos materiais retrobturadores, o Acroseal obteve a menor infiltração, seguido do MTA branco e do IBC BioAggregate. As amostras obturadas com o cimento Endofill não apresentaram diferença estatística em relação à variável tempo. Porém, nas amostras obturadas com o cimento AH Plus, houve maior ocorrência de infiltração nas amostras retrobturadas com o IBC BioAggregate e menor infiltração nas amostras retrobturadas com Acroseal, com diferença estatisticamente significante ao nível de 10%.The objective of this study was to compare the apical sealing ability of three root-end filling materials in teeth submitted to the microbial leakage by Enterococcus faecalis. Besides analyzing the occurrence of the microbial leakage in relation to the variable time.For such, 80 canine permanent superior teeth extracted from humans were used, which were instrumented with ProTaper Universal system (MAILLEFER) and filled by the lateral compaction technique, with two types of endodontic sealers: Endofill (DENTSPLY) and AH Plus (DENTSPLY). The apices were resected with the removal of 3mm of the apical third and the root-end cavities prepared with ultrasonic tips. The samples were subdivided, randomly, in 6 groups with 10 teeth each, and 2 control groups. The materials used for the retrofilling were white MTA (ANGELUS), IBC BioAggregate (INNOVATIVE BIOCERAMIX INC.) and Acroseal (SEPTODONT). Devices were made for fixation of the teeth to the Eppendorf tubes. The filling samples were inoculated with strains of E. faecalis and incubated at 37C, for a period of 90 days, for analysis of the presence of turbidity of Enterococcosel medium. For the accomplishment of the statistical analysis the following tests were used: Qui-square with Exact Proof of Fisher and Kruskal-Wallis. The results showed that all the groups in which the filling was accomplished and the subsequent retrofilling presented leakage. Comparing all groups, there was not significant difference among the tested materials. In regard to only the root-end filling materials, Acroseal obtained the smallest leakage, followed by white MTA and IBC BioAggregate. The samples filled with the sealer Endofill didn't present statistical difference in relation to the variable time. However, in the samples filled with the sealer AH Plus, there was larger leakage occurrence in the samples retrofilled with IBC BioAggregate and smaller leakage in the samples retrofilled with Acroseal, with statistically significant difference at a 10% level.
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Paes, Fabio Resende. "Infiltração microbiana em remanescentes de obturação de canais radiculares acrescidos de selador temporário." Universidade Federal de Uberlândia, 2006. https://repositorio.ufu.br/handle/123456789/16848.
Full textAbstract:
This study aimed to determine coronal leakage of root canals filling
remnants when employing Sealapex , used or don t used temporary
restorative materials Cotosol or Super Bonder, by means of differents
microbial indicators. Thus, 32 single-rooted human teeth were used,
which were shaped until the file size 50 and assigned to 4 groups. A
group was used as control. In the study model, a platform was employed,
which was split in two halves: an upper chamber where the microbial
suspension containing the biological indicators was introduced (E. faecalis
+ S. aureus + P. aeruginosa + B. subtilis + C. albicans); and a lower
chamber containing the culture medium Brain Heart Infusion, in which
3mm of the apical region of teeth were kept immersed. Interpretations of
the time to occur microbial leakage were made daily for 60 days, using the
turbidity of the culture medium which is indicative of microbial
contamination, as a reference. The data obtained were submitted to the
Kruskal-Wallis test. The results show that in the three: Group 1 -
remaining obturation with Sealapex of 5mm; Group 2 - remaining
obturation with Sealapex of 5mm and plug of 1mm Cotosol; Group 3 -
remaining obturation with Sealapex of 5mm and plug of 1mm Super
Bonder; didn t show statistical significant difference (p<0.05). In the group
1 didn t finding microbial leakage in 100% of the samples and for groups 2
and 3 in 87,5%.Estudou-se a infiltração microbiana em remanescentes de obturação de canais radiculares selados com guta-percha e cimento Sealapex, utilizando ou não um tampão com material selador temporário Coltosol ou o adesivo Super-Bonder. Trinta e dois dentes unirradiculares humanos extraídos foram utilizados e distribuídos aleatoriamente em quatro grupos experimentais com 08 amostras cada, sendo um controle. Para o modelo de estudo, empregou-se uma plataforma, dividida em duas partes: câmara superior onde foi introduzida a suspensão microbiana contendo os indicadores biológicos (E. faecalis + S. aureus + P. aeruginosa + B. subtilis + C. Albicans); e, câmara inferior, com o meio de cultura Brain Heart Infusion, onde os dentes permaneceram imersos com 3mm do remanescente apical radicular durante o período de 60 dias. Os dados obtidos foram submetidos ao teste estatístico Kruskal-Wallis. Os resultados mostraram que no grupo 1 - remanescente de obturação com Sealapex + guta-percha de 5mm não foi verificado infiltração microbiana em 100% das amostras; no grupo 2 - remanescente de obturação com cimento Sealapex + guta-percha de 5mm + tampão de 1mm de Cotosol e 3 - remanescente de obturação com cimento Sealapex + guta-percha de 5mm + tampão de 1mm de Super Bonder não foi verificado infiltração microbiana em 87,5% das amostras. Não houve diferença estatística significativa entre os três grupos, quanto à infiltração microbiana, decorridos 60 dias (p<0,05).
Mestre em Odontologia
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Filho, Solismar de Paiva Venzke. "Biomassa microbiana do solo sob sistema de plantio direto na região de Campos Gerais, Tibagi, PR." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/11/11138/tde-10022004-151043/.
Full textAbstract:
A demanda por informações relativas à ciclagem de nutrientes no solo sob sistema plantio direto (SPD) motivou o estudo das variações da biomassa microbiana do solo (BMS) em áreas com diferentes texturas submetidas há longo tempo a esse tipo de manejo. Na região de Campos Gerais, Tibagi (PR) é adotada a seqüência de culturas soja e milho no verão, seguidos de trigo e aveia preta no inverno há mais de 20 anos. O objetivo foi monitorar as variações do C e N-microbianos durante um ciclo de rotação em quatro áreas, sendo três com histórico de 12 anos sob SPD, com textura muito argilosa (PD12-TmuA), argilosa (PD12-TA), e média argilosa (PD12-TmeA), e uma com histórico de 22 anos sob SPD com textura argilosa (PD22-TA). No período de 18 meses foram realizadas nove amostragens de solo em quatro camadas (0-2,5; 2,5-5; 5-10; 10-20 cm). Foram avaliadas também alguns parâmetros das raízes do milho e da soja no PD22-TA visando determinar a influência de culturas distintas (plantas C4 e C3) sobre a concentração de BM no perfil do solo. A diferença de dez anos no tempo de adoção do SPD determinou aumento do C-microbiano no PD22-TA sobre o PD12-TA nas camadas mais profundas do solo. O PD22-TA também apresentou em média 30,8 kg Nmic.ha -1 mais BM-N que o PD12-TA na camada 0-20cm, com menor amplitude de variação. As diferenças na textura dos solos há 12 anos sob SPD resultou em maiores médias de C e N-microbiano na camada 0-20 cm na área mais argilosa (PD12-TmuA), exceto nos 20 dias após o plantio do trigo (jun/01). O PD12-TA e o PD12-TmeA não apresentaram diferenças significativas nas quantidades de C-microbiano somente na camada de 0-5cm. O C-microbiano apresentou correlação com o N-NH4 + e o N-NO3 - que o N-microbiano, independente da textura, do tempo de adoção SPD e da seqüência de culturas. O sistema radicular fasciculado do milho totalizou 1324 kg C ha -1 e 58 kg N ha -1 , com maior densidade por comprimento e por matéria seca de raízes ativas e raízes em vias de decomposição na camada superficial. O sistema radicular pivotante da soja (392 kg C ha -1 e 21 kg N ha -1 ) teve contribuição maior de raízes finas e densidade por comprimento do que o milho. O efeito das raízes do milho sobre o C-microbiano atingiu camadas mais profundas do que as raízes da soja. O N-microbiano foi estimulado pela concentração das raízes finas ativas e pelas raízes em decomposição ou de forma indefinida, possivelmente devido à maior concentração de C e N de fácil assimilação liberado ao solo. Concluiu-se que em função do tempo de adoção do SPD o C-microbiano aumenta em profundidade e o N-microbiano apresenta menor variação na camada 0-20 cm. A quantidade de C e N-microbiano é influenciada pela textura do solo. Entretanto, solos de classes textural próximas e sob SPD podem apresentar quantidades iguais de Cmicrobiano na camada 0-5 cm durante o sistema de produção.The demand for information about the nutrient cycling in soils under no-tillage motivated the study about soil microbial biomass (SMB) variations in different texture soils submitted for a long period to this kind of management system. The usual sequence of crops adopted for more than 20 years in Campos Gerais, Tibagi (PR) is soybean/corn during the summer and wheat/oats during the winter. The objective was to keep track of the microbial-C and N variations during a crop rotation cycle in four areas: three of them have been cultivated for 12 years under the no-tillage system, with a clay (PD12-TmuA), a sandy clay (PD12-TA), and a sandy clay loam (PD12-TmeA) texture, and a fourth, 22 years under the no-tillage system with a sandy clay loam textural class (PD22-TA). Nine soil samplings were performed during a period of 18 months, each time collecting four soil layers (0-2,5; 2,5-5; 5-10; 10-20 cm). Several corn and soybean root parameters were also evaluated in PD22-TA to determine the influence of diverse crops (C4 and C3 plants) on the microbial biomass concentration in the soil profile. The ten-year difference in no-tillage system adoption caused and increase of microbial-C in PD22-TA in relation to PD12-TA in the deeper soil layers. The PD22-TA also showed, on average, 30,8 kg Nmic.ha -1 more microbial-N than the PD12-TA in the 0-20 cm, with a narrower range of variation. The divergence in texture among the 12-year no-till sites resulted in higher microbial-C and N means in the 0-20 cm soil layer, except for 20 days after the wheat sowing. PD12-TA and PD12-TmeA did not show significant differences in the microbial-C amounts only for the 0-5cm layer. Microbial-C was more positively correlated with N-NH4 + and N-NO3 - than microbial-N, independently of soil texture, time since no-till adoption and crop sequence. The corn root system totaled 1324 kg C ha -1 and 58 kg N ha -1 in the upper soil layer, with higher density per length and per active root dry mass, and more roots in decomposition. The soybean root system (392 kg C ha -1 and 21 kg N ha -1 ) contributed more with fine roots and density per length than the corn. The effect of the corn root system on microbial-C reached deeper soil layers than the soybean roots. Microbial-N was stimulated by fine and active root concentration and by roots in decomposition phase, probably due to higher labile C and N concentration released to the soil. It was concluded that the microbial-C increased in depth along the period of no-till adoption, while the microbial-N showed less variation in the 0-20 cm soil layer. Both microbial-C and N are influenced by soil texture, although similar textural classes under no-till can maintain similar microbial-C amounts in the 0-5 cm soil layer during the crop production system.
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Guyonnet, Julien. "Effet de la stratégie de gestion des ressources des plantes sur l’investissement dans l’exsudation racinaire, et les conséquences sur les communautés bactériennes." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1008.
Full textAbstract:
L'exsudation racinaire est connue pour avoir une influence sur le fonctionnement des communautés microbiennes, en particulier celles impliquées dans le cycle de l'azote (Haichar et al, 2012). Elle est liée à la physiologie de la plante, cette dernière pouvant être évaluée via les traits fonctionnels végétaux, permettant une classification des plantes en fonction de leur performance dans leur environnement. Ainsi, nous pouvons distinguer d'une part les espèces exploitatrices, avec une efficience de la photosynthèse élevée et une acquisition rapide de l'azote dans les sols, et d'autre part les plantes conservatrices, possédant des caractéristiques contraires (Aerts & Chapin, 1999) et des plantes intermédiaires dont les caractéristiques sont intermediaires.L'objectif de ces travaux de thèse est de déterminer l'influence de la stratégie de gestion des ressources de 6 poacées, réparties le long d'un gradient de stratégie de gestion des ressources, allant de stratégies conservatrices (Sesleria caerulea et Festuca paniculata), intermédiaires (Antoxanthum odoratum, Bromus erectus) à des stratégies exploitatrices (Dactylis glomerata et Trisetum flavescens), sur la diversité et le fonctionnement des communautés totales et dénitrifiantes. I) Dans un premier temps nous avons étudié le lien entre la stratégie de gestion de ressources des plantes et la quantité d'exsudats racinaires dans le sol adhérent aux racines (SAR). Nous avons ensuite déterminé l'influence de la quantité d'exsudats racinaire sur les activités microbiennes potentielles des communautés microbiennes du SAR (respiration et dénitrification potentielles), puis par une approche ADN-SIP (Stable Isotope Probing) couplée à du séquençage haut-débit, l'influence de l'exsudation racinaire sur la structure et la diversité des communautés bactérienne colonisant le SAR et le système racinaire. II) Dans un second temps, nous avons étudié le lien entre la stratégie de gestion des ressources des plantes et la nature des exsudats racinaires libérés au niveau du SAR et présents dans les extraits racinaires en analysant les profils des métabolites primaires chez Festuca paniculata, Bromus erectus et Dactylis glomerata, représentant respectivement des stratégies de gestion des ressources conservative, intermédiaire et exploitatriceRoot exudation is known to influence microbial communities functioning, in particular those involve in nitrogen cycle. (Haichar et al, 2012). It’s linked to plant physiology, which can be evaluated with functional traits, allowing a plant distribution in function of their performance in their environment. Thus, we can distinguish competitive species, with higher photosynthetic capacity and rapid rates of N acquisition, conservative species with the opposite characteristics (Aerts & Chapin, 1999) and intermediate plants, with intermediate characteristics.The objective of this work is to determinate the influence of nutrient management strategiy of 6 poaceae, along a strategies gradient from conservative strategy (Sesleria caerulea and Festuca paniculata), intermediate (Antoxanthum odoratum and Bromus erectus) to competitive strategy (Dactylis glomerata and Trisetum flavescens), on diversity and functioning of total and denitrifying communities.I) Firstly, we studied the link between the plant nutrient management strategy and the root exudates quantity in the root adhering soil (RAS). Then, we determined the influence of the rate of root exudation on potential microbial activities (respiration and denitrification), and with a DNA-SIP (Stable Isotope Probing) approach coupled to high-throughput sequencing, the influence of root exudation on the bacterial structure and diversity of communities colonizing the RAS and the root system. II) Secondly, we studied the link between the plant nutrient management strategy and the nature of molecules exuded in RAS and present in root extracts by analyzing primary metabolites profile to Festuca paniculata, Bromus erectus and Dactylis glomerata, respectively a conservative, an intermediate and a competitive plant. Then, we determined the influence of primary metabolites profile of each plant on semi-real denitrification of communities colonizing RAS of plants. III) Finally, an mRNA-SIP approach is in progress to determine the influence of exuded metabolites on active bacterial communities functioning and the expression of genes involved in denitrification process in RAS and root system. Our results show an influence of the nutrient management strategy on the rate of carbon exudation, the competitive plants exuding more than conservatives ones
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Suárez, Díaz Javier. "Methodological strategies in contemporary symbiosis research and their historical roots: From mechanistic to non-mechanistic modes of explanation." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/668997.
Full textAbstract:
Symbiosis research is a growing field in contemporary biology. Current advances in modelling and experimental techniques have made possible to develop new ways of studying some multispecies symbiotic systems whose study had been mostly ignored in the past. Some of these new modelling and experimental techniques rely on the use of sophisticated mathematical tools (such as network analysis) that can only be used if the system is conceived holistically. One of the main consequences of this approach is that de-composition becomes an impossible task: if biologists want to understand how some multispecies symbiotic systems work, how they behave, or how they evolve, they need to study the system holistically, rather than study how each of the parts of the system relates to each other. This type of research seems to question the dominant tradition in contemporary philosophy of science and biology, namely: new-mechanism. According to the principles of new-mechanistic philosophy, biological systems need to be de- composed in their component elements to properly understand how they work, and in order to unveil the causal connections among the components. The purpose of this doctoral thesis is to understand how contemporary symbiosis research questions some of the core philosophical thesis that underlie new-mechanistic philosophy. To do so, the thesis will rely on two philosophical methods: (1) analysis of scientific practise; (2) conceptual analysis. By applying these two methods to contemporary symbiosis research, the thesis gives rise to three papers in specialized journals, added as annexes. The key original contribution of the doctoral dissertation is that contemporary symbiosis research relies on the use of certain mathematical methods that are only applicable if the system is studied holistically, and thus entail a form of non-causal-mechanistic explanation. In the end, several open questions for future research are presented.La investigación sobre la simbiosis es un campo en crecimiento en la biología contemporánea. Los avances actuales en el modelado y las técnicas experimentales han permitido desarrollar nuevas maneras de estudiar algunos sistemas simbióticos de múltiples especies cuyo estudio había sido ignorado en el pasado. Algunas de estas nuevas técnicas experimentales y de modelado se basan en el uso de herramientas matemáticas sofisticadas (como el análisis de redes) que solo se pueden emplear si el sistema se concibe de manera holística. Una de las principales consecuencias de este enfoque es que la descomposición del sistema en partes se vuelve una tarea imposible: si los biólogos quieren comprender cómo funcionan algunos sistemas simbióticos de múltiples especies, cómo se comportan o cómo evolucionan, deben estudiar el sistema de manera holística, en lugar de estudiar cómo cada una de las partes del sistema se relaciona entre sí. Este tipo de investigación parece cuestionar la tradición dominante en la filosofía contemporánea de la ciencia y la biología, a saber: el nuevo mecanismo. De acuerdo con los principios de la filosofía del nuevo mecanicismo, los sistemas biológicos deben descomponerse en sus elementos componentes para comprender adecuadamente cómo funcionan y para descubrir las conexiones causales entre los mismos. El propósito de esta tesis doctoral es comprender cómo la investigación contemporánea sobre simbiosis cuestiona algunas de las tesis filosóficas centrales que subyacen a la filosofía del nuevo mecanismo. Para hacerlo, la tesis se basará en dos métodos filosóficos: (1) análisis de la práctica científica; (2) análisis conceptual. Al aplicar estos dos métodos a la investigación contemporánea sobre simbiosis, la tesis da lugar a tres artículos en revistas especializadas, que se agregan como anexos. La contribución original clave de la disertación doctoral es que la investigación contemporánea sobre la simbiosis se basa en el uso de ciertos métodos matemáticos que solo son aplicables si el sistema se estudia de manera holística y, por lo tanto, conlleva una forma de explicación no mecanicista y no causal. Al final, se presentan varias preguntas abiertas para futuras investigaciones.
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Lusley, Pauline. "Compréhension des mécanismes directs et indirects de résistance à la pourriture racinaire du pois causée par Aphanomyces euteiches : influence du choix variétal et de la cohorte microbienne associée. Compared analysis of architectural symptoms and disease severity caused by Aphanomyces euteiches between winter and spring peas. Co-existence of Rhizobia and non-rhizobial bacteria in the nodules of Pisum sativum L. depending on cultivars and influencing mycelium growth of Aphanomyces euteiches. The microbial cavalry: how crop could be determinant to beneficially shape soil microbiome in the battlefield against Aphanomyces euteiches." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR091.
Full textAbstract:
Le pois protéagineux, dont la culture est bien adaptée au contexte pédoclimatique normand, représente une source nutritive importante en protéines végétales. A l’heure actuelle, les cultures protéagineuses font partie des cultures d’avenir aux vues de leurs nombreux intérêts agronomique, économique et environnemental. Malgré ses multiples atouts, la culture du pois protéagineux n'a pas autant de succès, principalement en raison d’une forte atteinte par diverses phytopathologies, dont le plus préjudiciable est la pourriture racinaire du pois causée par Aphanomyces euteiches. Les dégâts occasionnés peuvent conduire à une baisse importante du rendement et ainsi pénaliser les agriculteurs. Ne disposant d’aucun traitement efficace à ce jour, il est donc important de focaliser les recherches sur le développement de moyens de contrôle, ce qui passe par une compréhension holistique du pathobiome. Dans cette thèse, les travaux se sont concentrés sur la compréhension de certains mécanismes de résistance directs ou indirects à la pourriture racinaire du pois causée par A. euteiches, en se focalisant sur l’étude de la contribution des facteurs biotiques, à savoir, le génotype variétal, seul ou accompagné de son phytobiome, et donc la mise en place de multiples interactions avec les microorganismes. L’analyse comparée de l’expression de la maladie et des modifications architecturales induites a montré une expression différentielle de la maladie selon leur appartenance au groupe hiver ou printemps. Les variétés d’hiver caractérisées par une grande tolérance au froid présentent 2 traits d’intérêt : un retard d’impact sur les parties aériennes malgré une atteinte racinaire et un accroissement du système racinaire en réponse à l’infection. De plus, l’étude de la diversité bactérienne intra-nodules chez ces mêmes variétés de pois d’hiver et de printemps, a montré que la diversité de ce microbiome endophyte varie en fonction du génotype variétal. Cette étude a permis de déceler le fort potentiel biocontrôle des endophytes bactériens intra-nodulaires, avec une abondance relative observée des genres bactériens connus pour leurs effets antagonistes envers A. euteiches plus importante chez deux variétés de pois d’hiver. Le génotype variétal constitue donc un levier, direct et indirect via l’établissement d’interactions avec des microorganismes bénéfiques, pour lutter contre la pourriture racinaire du pois. Le dernier axe de recherche a démontré la forte influence des espèces cultivés sur les associations microbiennes au sien de la rhizosphère, en particulier sur l’assemblage des populations bénéfiques. La manipulation de la composition des communautés microbiennes par les couverts végétaux au bénéfice de la culture suivante représente un argument de plus en faveur de l’utilisation des rotations des cultures comme levier contre les phytopathologies. Plusieurs pistes intéressantes ressortent donc de ce travail, pour une lutte efficiente et globale contre A. euteiches : à l’échelle de la variété, par ses caractéristiques propres en lien avec son génotype et sa capacité à sélectionner des endophytes protecteurs, et à l’échelle de la rotation, par la manipulation du microbiome en faveur du pois. De belles perspectives de recherche se profilent, notamment la réalisation de tests d’efficacité de protection de tous les potentiels agents de biocontrôles isolés, qui permettraient la mise en oeuvre de consortia bénéfiques adaptés au terroir normand et aux spécificités variétales du poisPea, well-adapted to the Normandy pedoclimatic context, represents an important nutritional source of plant proteins. At present, protein crops are among the promoting crops in view of their many agronomical, economic, and environmental interests. Despite their multiple advantages, the cultivation of protein peas is not as successful, mainly due to strong attacks by various phytopathology. The most damaging is pea root rot caused by Aphanomyces euteiches leading to a significant drop in yield and thus can penalize farmers. As there is no effective treatment to date, numerous focus researches are in progress to develop efficient control methods, which requires a holistic understanding of the pathobiome. In this thesis, studies were focused on the understanding of some direct and indirect resistance mechanisms of pea root rot caused by A. euteiches. The contribution of biotic factors in this disease were studied, specifically the influence of varietal genotype and its associated phytobiome, and so the establishment of multiple interactions with microorganisms. The comparative analysis of disease severity and induced architectural modifications, showed a differential expression according to their affiliation to winter or spring group. The two winter pea cultivars characterized by a high cold tolerance presented two features of interest: a delayed impact on aerial part despite significant root damage and an increased growth of root system in response to infection. In addition, the study of intra-nodule bacterial diversity in these same cultivars showed that the diversity of their nodule microbiome varies according to varietal genotype. This study highlighted the strong biocontrol potential of intra-nodule bacterial endophytes, with a higher relative abundance of known antagonistic bacterial genera towards A. euteiches for two winter pea cultivars. The varietal genotype therefore constitutes a direct and indirect lever by the establishment of interactions with beneficial microorganisms, to fight against pea root rot. The last research line has demonstrated the strong influence of plant cultivated species on the microbial associations in the rhizosphere, specifically a modulation of the assemblage of beneficial populations. Shaping the microbial community composition though the cultivation of crops to the benefit of the next crop represents an additional argument in favor of crop rotation use as a lever against phytopathology. Several interesting alternatives were highlighted in this research work to effectively and efficiently manage A. euteiches: at the cultivar scale, by specific characteristics in relation to varieties’ genotype and their ability to select protective endophytes, and at the scale of crop rotation, by shaping microbiome in favor of pea. Great research perspectives are emerging, especially the efficiency of protection resulting from all potential isolated biocontrol agents, which would allow the development and implementation of beneficial consortia adapted to Normandy soils and to pea cultivars specificities
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Yang, Luhua [Verfasser], Michael [Akademischer Betreuer] Schloter, Caroline [Gutachter] Gutjahr, and Michael [Gutachter] Schloter. "The role of the seed microbiome of barley (Hordeum vulgare) as driver for the composition of root endophytes / Luhua Yang ; Gutachter: Caroline Gutjahr, Michael Schloter ; Betreuer: Michael Schloter." München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/1215293399/34.
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Andrade, Laíse de Oliveira. "Métodos rápidos para identificação microbiana aplicados ao monitoramento ambiental de salas limpas: ênfase na tecnologia MALDI-TOF." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/9/9139/tde-26102017-114152/.
Full textAbstract:
A espectrometria de massas baseada na tecnologia MALDI-TOF (do inglês, matrix-assisted laser desorption ionization-time of flight) (MALDI-TOF MS) tem sido cada vez mais incorporada à rotina de identificações microbiológicas nos laboratórios farmacêuticos de controle de qualidade, principalmente para as atividades do Programa de Monitoramento Ambiental de Salas Limpas. Isso porque o longo tempo necessário para a obtenção dos resultados por meio de métodos convencionais tem incentivado a procura por técnicas que permitam métodos rápidos. O objetivo deste trabalho foi avaliar a adequação da técnica MALDI-TOF MS para a identificação de bactérias isoladas do ambiente de salas limpas utilizadas em algumas etapas da produção de uma vacina viral. Treze espécies bacterianas conhecidas, normalmente isoladas das salas limpas estudadas, e cinco cepas ATCC foram identificadas pela técnica MALDI-TOF MS e por uma técnica bioquímica (BBL Crystal®). O desempenho da técnica MALDI-TOF MS foi superior ao da técnica bioquímica na identificação correta das espécies bacterianas (88,89% e 38,89%, respectivamente) e produziu menos identificações não confiáveis (5,55% e 22,22%, respectivamente). Os resultados evidenciaram que a técnica MALDI-TOF MS pode ser implementada para identificação rotineira de bactérias em um laboratório de controle de qualidade farmacêutico. Entretanto, a dependência de bases de dados exige estudos adicionais de isolados não identificados e, se apropriado, a adição destes a uma base de dados interna. O aperfeiçoamento de métodos de identificação microbiana é muito relevante no contexto de salas limpas, pois permitem ações corretivas e proativas essenciais para garantir a segurança microbiológica do processamento asséptico.Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been increasingly introduced in routine microbiological identifications of pharmaceutical quality control laboratories, mainly for the activities of the Environmental Monitoring Program of Clean Rooms. The long time needed to obtain the results through conventional methods has stimulated the search for techniques that allow rapid methods, as MALDI-TOF MS. Thus, the objective of this work was to evaluate the suitability of the MALDI-TOF MS technique for the identification of bacteria isolated from the environment of clean rooms used in some stages of the production of a viral vaccine. Thirteen bacterial species commonly isolated from clean rooms studied and five strains ATCC were identified by MALDI-TOF MS technique and by a biochemical technique (BBL Crystal® System). Performance of MALDI-TOF MS was better than biochemical technique for correct species identifications (88.89% and 38.89%, respectively) and produced fewer unreliable identifications (5.55% and 22.22%, respectively). MALDI-TOF MS can be implemented for routine identification of bacteria in a pharmaceutical quality control laboratory. However, as a database-dependent system, maybe some isolated not identified by this technique must be additionally studied and, if appropriate, added to an in-house database.
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Raveau, Robin. "Contribution au développement d’une filière éco-innovante de phytomanagement de sols pollués par les éléments traces : culture de plantes aromatiques et production d’huiles essentielles The Aromatic Plant Clary Sage Shaped Bacterial Communities in the Roots and in the Trace Element-Contaminated Soil More Than Mycorrhizal Inoculation – A Two-Year Monitoring Field Trial." Thesis, Littoral, 2020. http://www.theses.fr/2020DUNK0580.
Full textAbstract:
Le phytomanagement compte parmi les méthodes innovantes de gestion des sites et sols pollués en raison de son adéquation avec le développement durable. Pour répondre à la double exigence de performances environnementales et économiques, les phytotechnologies sont désormais combinées à la valorisation de la biomasse produite sur sols pollués. Parmi les filières éco-innovantes et non-alimentaires de valorisation de cette biomasse, la culture de plantes à parfums, aromatiques et médicinales (PPAM) pour la production d’huiles essentielles (HE), substances biosourcées à haute valeur ajoutée, a été proposée dans le cadre du projet PhytEO, financé par l’ADEME. Ainsi, ma contribution à ce projet a permis d‘évaluer la pertinence d’un mode de gestion reposant sur la culture de la sauge sclarée et de la coriandre, en présence ou non d’un amendement mycorhizien, en s’appuyant sur des démonstrateurs in situ à l’échelle de l’hectare, parcelles historiquement polluées ou non par les éléments traces (ET). La coriandre ainsi que la sauge sclarée ont toutes deux montré une bonne capacité à s’installer, à se développer et à produire une quantité importante de biomasse sur des sols présentant une forte pollution historique par les ET. Bien que l’ajout d’un amendement biologique à base de champignons mycorhiziens à arbuscules ait permis d’augmenter de façon significative les taux de mycorhization des racines de coriandre et de sauge sclarée, aucun gain n’a été observé ni au niveau de la croissance de ces deux PPAM, ni au niveau de la quantité et de la qualité des HE. Un effet positif en termes d’immobilisation des ET dans le sol, en particulier du Pb, et une réduction des transferts des ET (Cd et Pb) dans les parties aériennes a toutefois été montré chez la sauge sclarée. D’autre part, les HE distillées à partir de la biomasse de sauge sclarée (inflorescences) ou de coriandre (parties aériennes ou graines) cultivées sur sols pollués présentent une qualité très satisfaisante, caractérisée par leur non contamination en ET ou en résidus de pesticides (traces). Leurs compositions chimiques, non altérées par la pollution en ET et l’inoculation mycorhizienne, affichent divers principes actifs dont le linalol, l’acétate de linalyle, le germacrène, l’α-pinène, le γ-terpinène, le 2-décénal, le décanal et le 2-dodécénal. Ainsi, plusieurs propriétés biologiques potentiellement valorisables dans des domaines à vocation non-alimentaire, tels que la protection des cultures (effets fongistatiques, anti-germinatifs et herbicides) ou la santé humaine (effets anti-inflammatoires et antioxydants) ont été mises en évidence. En revanche, en dépit de son fort pouvoir complexant des HE, la β-cyclodextrine n’a montré aucun effet positif sur les propriétés biologiques testées. Par ailleurs, la végétalisation du sol pollué par la sauge sclarée permet une modulation de la structure des communautés bactériennes et fongiques, telluriques et racinaires. Enfin, l’ensemble des résultats de cette étude et de l’analyse technico-économique de la filière PPAM-HE soulignent le haut potentiel de la sauge sclarée dans une démarche de phytomanagement de sols pollués par les ETTo cope with the soil trace element (TE) pollution, phytomanagement was brought forward as an eco-friendly and feasible approach. To meet the dual requirements of environmental and economic performances, phytotechnologies are now combined with the valorisarion of biomass produced on polluted soils. Among the eco-innovative channels intended for the non-food valorisation of the produced biomass, the cultivation of aromatic and medicinal plants producing essential oils (EO), high-added value biosourced products, has been suggested within the framework of PhytEO project, funded by ADEME. Thus, this thesis contributed to evaluate the relevance of a management approach based on clary sage and coriander cultivation, combined or not with a mycorrhizal inoculum, on in situ experimental plots polluted or not with TE. Both clary sage and coriander have shown a good ability to settle in, to grow and to produce high amounts of biomass, despite the presence of high TE concentrations in the soil. The addition of an amendment based on arbuscular mycorrhizal fungi enhanced the mycorrhizal colonisation rates of both coriander and clary sage roots. However, no significant improvement was observed in terms of plants’ growth, EO amounts and quality. Moreover, mycorrhizal inoculation allowed TE immobilisation in soils, in particular Pb, and reduced TE (Cd and Pb) transfers in aerial parts of clary sage. Besides, the EO distilled from clary sage inflorescences and coriander (aerial parts orseeds) grown on TE polluted soils, displayed a highly satisfactory quality, regarding the absence of contamination by TE or pesticide residues (trace amounts). Their chemical compositions were not altered by both TE pollution and mycorrhizal inoculation and were characterized by several active principles, such as linalool, linalyl acetate, germacrene, α-pinene, γ-terpinene, 2-decenal, decanal and 2-dodecenal. Furthermore, several biological properties with potential applications in non-food fields such as crop protection (antifungal, antigerminative and herbicidal) or human healthcare (antioxidant and anti-inflammatory) have been brought forward. However, despite its ability to form inclusion complexes with EO components, β-cyclodextrin has shown no significant improvement of the tested EO biological activities. On another note, the soil revegetation with clary sage displayed a clear shaping of the bacterial and fungal communities, in both the rhizospheric soil and the roots of the aromatic plant species. Altogether, our results combined with the techno-economic feasibility assessment of the channel “aromatic and medicinal plants/EO” have emphasised clary sage as a good candidate for the phytomanagement of TE-polluted soils
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Delgado, Ronan Jacques Rezende. "Avaliação in vitro da viabilidade de Enterococcus faecalis e Candida albicans nos túbulos dentinários após a aplicação de hidróxido de cálcio e clorexidina gel 2%." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/25/25138/tde-18102007-155525/.
Full textAbstract:
Uma infecção pulpar pode resultar na colonização microbiana de todo sistema de canais radiculares incluindo os túbulos dentinários. Estes microorganismos e seus produtos tóxicos são responsáveis pelo desenvolvimento e persistência da periodontite apical de origem endodôntica. O presente estudo objetivou avaliar a viabilidade de E. faecalis e C. albicans em túbulos dentinários após a aplicação de hidróxido de cálcio, clorexidina gel 2%, hidróxido de cálcio associado à clorexidina gel 2% e soro fisiológico, através da análise por cultura microbiológica e microscopia de fluorescência. Para tanto 120 raízes de dentes humanos foram padronizadas e autoclavadas, sendo posteriormente divididas em 2 grupos (n= 60) para contaminação com E. faecalis e C. albicans por 21 dias. Em seguida, foram divididas em 8 grupos (n= 15) para aplicação das substâncias antimicrobianas nos canais radiculares e posterior incubação em estufa por 14 dias. Amostras da dentina radicular na extensão de 0 - 100 µm e de 100 - 200 µm foram coletadas e submetidas à cultura microbiológica através do plaqueamento em meios de cultura. Após 48 horas de incubação promoveu-se a avaliação das UFC. Paralelamente, as amostras foram processadas para análise em microscopia de fluorescência com auxílio de marcadores fluorescentes específicos, a fim de se determinar a proporção de microorganismos viáveis e não viáveis. Outros 6 espécimes foram preparados para análise em MEV. Os resultados mostraram uma maior capacidade de penetração intratubular para E. faecalis quando comparado a C. albicans. A aplicação de medicação intracanal resultou em significativa redução da viabilidade dos microorganismos quando comparado ao grupo controle independente da medicação aplicada e em ambas as porções da dentina radicular avaliadas. Entretanto, ao compararmos individualmente as medicações, observamos o melhor desempenho da clorexidina gel 2 % e da associação de hidróxido de cálcio e clorexidina gel 2% sem diferença significante entre elas. O hidróxido de cálcio apresentou os piores resultados para desinfecção dos canais radiculares contaminados com E. faecalis e C. albicans. Estes achados foram confirmados tanto pela cultura microbiológica quanto pela microscopia de fluorescência. A cultura microbiológica e a microscopia de fluorescência são métodos adequados e complementares para avaliação da viabilidade de E. faecalis e C. albicans e a eficácia da clorexidina gel 2% e da associação hidróxido de cálcio e clorexidina gel 2% justificam seu uso em endodontia como medicação intracanal.A pulp infection can result in a microbial colonization of the entire root canals system, including dentinal tubules. These microorganisms and their toxic product are responsible for the development and persistence of apical periondontitis from endodontic source. The present study aimed to evaluate E. faecalis and C. albicans viability in dentinal tubules after the application of calcium hydroxide, chlorhexidine gel 2%, calcium hydroxide associated to chlorhexidine gel 2% and physiological solution, through the analysis by microbiological culture and fluorescence microscopy. For that, 120 human teeth root were standardized and submitted to autoclave, and after ere divided into 2 groups (n=60) for E. faecalis and C. albicans contamination for 21 days. Following this, they were divided into 8 groups (n=15) for application of antimicrobial substances in the root canals and subsequent incubation for 14 days. Samples from root dentin with 0 - 100 µm and 100 - 200 µm of extension were collected and submitted to microbiological culture.After 48 hours of incubation, it was performed the evaluation of colony-forming units (CFU). At the same time, the samples were processed for fluorescence microscopic analysis with the assistance of specific fluorescent markers, in order to determine the proportion of viable and non-viable microorganisms. Other 6 specimens were prepared for the analysis of scanning electron microscopy. Results demonstrated a higher capacity of penetration in the tubules for E. faecalis than for C. albicans. The application of intracanal medication resulted in significant reduction of microorganisms viability when compared to the control groups independently of the medication used and in both evaluated portions of root dentin. However, when one compares individually the medications, it was observed a better performance of chlorhexidine gel 2% and the association of calcium hydroxide with chlorhexidine gel 2% without a significant difference between them. Calcium hydroxide had the worst results for disinfection of root canal contaminated with E. faecalis and C. albicans. These findings were confirmed for the microbiological culture as well as for the fluorescence microscopy. The microbiological culture and the fluorescence microscopy are adequate methods and complementary for the evaluation of E. faecalis and C. albicans viability and the efficacy of chlorhexidine gel 2% and the association of calcium hydroxide with chlorhexidine gel 2% warrant their use in Endodontics as an intracanal medication.
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Rosa, Victoria Christina Scarano Figueira Paes. "Eficácia dos sistemas rotatórios e reciprocantes na redução microbiana - revisão narrativa." Master's thesis, 2020. http://hdl.handle.net/10284/9385.
Full textAbstract:
Sendo os micro-organismos o principal fator de insucesso do tratamento endodôntico,
um aspeto preponderante para um tratamento eficiente é providenciar uma redução
microbiana máxima do canal radicular.
Os diferentes sistemas de instrumentação em Endodontia foram sempre evoluindo com
o propósito de fornecer ao paciente e ao profissional um tratamento mais rápido, seguro
e eficaz.
Este trabalho tem como objetivo analisar e comparar alguns dos sistemas rotatórios e
reciprocantes disponíveis no mercado, com o intuito de definir qual deles permite uma
maior redução do número de micro-organismos no canal radicular e consequentemente,
permite obter um melhor tratamento endodôntico.
Embora todos os sistemas estudados terem apresentado eficácias similares na redução
microbiana, alguns trabalhos mostraram diferenças relevantes no que concerne ao
preparo do canal radicular.
Este fato torna necessário a realização de novos estudos para avaliar os diferentes
sistemas disponíveis no mercado e suas respetivas eficácias na redução microbiana.As microorganisms are the main factor of failure during the endodontic treatment, a preponderant aspect for an efficient treatment is to provide a maximum microbial reduction of the root canal. The different systems of instrumentation in Endodontics have always been evolving with the purpose of providing to the patient as to the professional a faster, safer and more effective treatment. This work aims to analyze and compare some of the rotational and reciprocating systems available in the market, with the intention of defining which of them allows a greater reduction in the number of microorganisms in the root canal and consequently, allows to obtain a better endodontic treatment. Although all the systems studied presented similar efficiency in microbial reduction, some studies showed relevant differences in the preparation of the root canal. This makes it necessary to carry out new studies to evaluate the different systems available in the market and their respective efficiency in microbial reduction.
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Whatley, Jenny J. (Jenny Johnson) 1982. "An in-vitro evaluation on the biocompatibility of resilon by the microbiota of the infected root canal utilizing an agar disc diffusion assay." Thesis, 2012. http://hdl.handle.net/1805/3093.
Full textAbstract:
Indiana University-Purdue University Indianapolis (IUPUI)Resilon is a resin-based obturation material that claims to create a monoblock through bonding of RealSeal sealer to the dentin walls and to the core material. Resilon is comprised of a biodegradable polymer, polycaprolactone, and inorganic fillers. Resilon has been shown to undergo enzymatic hydrolysis by bacterial enzymes such as lipase. This study aims to demonstrate if bacteria found within the infected root canal system are capable of degrading Resilon utilizing an agar disc hydrolysis method. A 0.1-percent Resilon emulsion and a gutta-percha emulsion were prepared with Tryptic Soy Agar in plates. Several bacterial species were inoculated in eight spots each on the Resilon and gutta-percha agar plates and the plates were observed for the formation of hydrolytic halos surrounding bacteria signifying their ability to degrade the material. The bacterial enzyme Lipase PS served as a positive control. P. intermedia, P. aeruginosa, P. assacharoylitica, S. epidermidis and S. aureus all demonstrated hydrolytic halos, clear zones, at each of the eight inoculation locations (100%, 95%CI 63%-100%) on the Resilon plates. The halos were similar to those seen in the positive lipase control. No halos were seen with E. faecalis, F. nucleatum, S. mutans, S. sanguis, or P. gingivalis at any of the eight inoculation spots (0%, 95%CI 0%-37%) on the Resilon plates. No hydrolytic halos were seen around any bacterial colonies or the Lipase PS on the gutta-percha plates. The results of this study indicate that bacteria found in endodontic infections can hydrolize Resilon dispersed into an emulsion. The potential exists for Resilon degradation after its use as an obturation material in infected root canal systems. Given that root canal therapy does not render a canal void of microorganisms, it is prudent to obturate the root canal system with a material that cannot be degraded by bacteria and their enzymes.
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Johnston, Monje David Morris. "MICROBIAL ECOLOGY OF ENDOPHYTIC BACTERIA IN ZEA SPECIES AS INFLUENCED BY PLANT GENOTYPE, SEED ORIGIN, AND SOIL ENVIRONMENT." Thesis, 2011. http://hdl.handle.net/10214/2747.
Full textAbstract:
Endophytes are organisms that live inside plants without causing disease and include microbes that benefit their hosts by aiding in nutrient acquisition and pathogen control. This thesis concerns the endophytes of the genus Zea which includes modern maize (Zea mays L.). Beginning 9,000 years ago, maize was domesticated from wild grasses in Mexico (teosintes), bred into diverse varieties and moved to new soils throughout the Americas. The impact of these long-term changes on the associated endophytic communities has not been examined. Furthermore, today, maize is routinely transplanted around the world to facilitate breeding, but the short-term impact of switching soils on endophyte composition is not known. I attempted to answer the first question by surveying the bacterial endophytes that inhabit 14 diverse ancestral, ancient and modern Zea genotypes. To answer the second question, three extreme Zea genotypes, ancestral, intermediate and modern, were grown side by side on two extreme soils that span the tropical-to-temperate migration route of maize. Endophyte populations from seeds, roots and shoots were DNA fingerprinted using terminal restriction length polymorphism (TRFLP) of 16S rDNA. To understand microbial functions, bacteria were cultured and tested for >13 in vitro traits including nitrogen fixation, phosphate solubilization, plant hormone production and antibiosis. Relationships between endophyte communities were analyzed using principle component analysis (PCA) and Sᴓrensen’s similarity index. The results show that different Zea tissues and genotypes have diverse endophytic communities. The community composition of seed endophytes correlates with host phylogeny suggesting that as humans bred maize, they inadvertently impacted its microbial inhabitants, though the change was gradual. Soil swapping and growth on sterile sand confirm that shoot and root endophyte communities in juvenile plants are primarily inherited. However, a given maize genotype can also select and take up the same microbes (based on TRFLP) from geographically diverse soils. These latter results show that the endophyte communities of Zea plants are significantly buffered from the short-term effects of migration. A few microbes and microbial traits are conserved across all Zea genotypes and soil treatments, suggestive of a core taxonomic and functional microbiota for this agriculturally important genus.OMAFRA New Directions, Ontario Research Fund, Canadian Foundation for Innovation
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Noortje, Notenbaert. "The effect of selective breeding and genetic manipulation on the microbiome surrounding maize roots." Thesis, 2018. http://hdl.handle.net/2097/38860.
Full textAbstract:
Master of ScienceDepartment of Agronomy
Charles W. Rice
Maize (Zea mays L.) is a major staple crop whose wild ancestor was domesticated about 9,000 years ago (Beadle, 1939). Long-term breeding for more desirable traits ultimately resulted in the maize we see today. This long-term breeding likely impacted the processes within the rhizosphere of maize, however, to what extent is not well understood. This study examined the microbial communities between an inbred maize line (B73), a hybrid of two isogenic lines (B73xMo17), and two genetically modified maize hybrids (DKC63-55RIB and DKC64-69RIB) to determine if the plant’s ability to attract beneficial microbes changed with breeding. The hypothesis was that the isogenic cultivar forms better relationships with bacteria and fungi compared to the newer cultivars, especially in low P soil. It was also expected that the greater the difference between the cultivars the more distinct their soil microbiome. To test these hypotheses, experiments were conducted under greenhouse and field conditions. Analyses consisted of root staining to test symbiotic relationships, phospholipid fatty acid analysis (PLFA) for microbial communities, total plant and root biomass, and nutrient content to understand plant responses. Based on the field results, there was no impact on root and shoot biomass and nutrient content by differences in cultivar. Differences in cultivar did impact arbuscular mycorrhizal fungi (AMF) colonization, which decreased over time and depth for all. Soil AMF also saw a significant effect by cultivar. Other microbial groups were not impacted by cultivar, were greatest in the control, and decreased over time. Greenhouse results showed a cultivar by time interaction for root and shoot biomass. Soil P also impacted shoot biomass, but not root biomass. Shoot nutrient content was greater in high P soil, while roots only saw an impact for root P. No cultivar effect was found for soil microbial groups except for fungi, while all microbial groups were reduced in the control soil. Most soil microbial groups were also impacted by soil P as indicated by reduced concentrations in low P soil. AMF was the only microbial group that was not negatively impacted by limited soil P. In addition, all soil microbial groups increased over time, although fungi saw a decrease at R1. No significances were observed for percent AMF colonization.
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Véliz, Vallejos Debora Fabiola. "The effect of quorum sensing signals on nodulation of Medicago truncatula." Phd thesis, 2016. http://hdl.handle.net/1885/111187.
Full textAbstract:
N-acyl homoserine lactones (AHLs) act as quorum sensing signals
that regulate cell-density dependent behaviours in many
gram-negative bacteria, in particular those important for
plant-microbe interactions. AHLs can also be recognised by
plants, and this may influence their interactions with bacteria.
This thesis tested whether the exposure to AHLs affects the
nodule-forming, nitrogen-fixing symbiosis between legume hosts
and rhizobia. It used the legume, Medicago truncatula, and its
symbiont, Sinorhizobium meliloti, as this model symbiosis has
been well characterised on a molecular and cellular basis. In
addition, previous studies have characterised the identities and
roles of AHLs from S. meliloti during nodulation.
First, protocols were established to grow M. truncatula plants
under conditions conducive to symbiosis and, at the same time, to
minimise growth of bacteria growing in and on roots. This was
important as bacteria can destroy AHLs and could thus interfere
with externally applied AHLs. M. truncatula was found to harbour
culturable bacteria that were derived from the inside of the seed
coat and were recalcitrant to surface sterilisation. A protocol
using an antibiotic treatment of the seeds to minimise bacterial
growth, and an axenic system growing M. truncatula seedlings on
large agar plates was chosen for subsequent experiment.
M. truncatula seedlings were exposed to a range of synthetic AHLs
derived either from its specific symbiont, S. meliloti, or from
the potential pathogens, Pseudomonas aeruginosa and Agrobacterium
vitis. Increased numbers of nodules formed on root systems
treated with the S. meliloti-specific AHL, 3-oxo-C14-homoserine
lactone (HSL), while the other AHLs did not result in significant
changes to nodule numbers. The increase in nodule numbers was
dependent on AHL concentrations and was repeatedly observed at
concentrations of 1 M and above. No evidence for altered
nodule invasion by the rhizobia was found. 3-oxo-C14-HSL
‘primed’ Medicago plants before inoculation with rhizobia,
indicating that the increase in nodule numbers occurs at early
stages and as a direct effect on the plant and not on the
rhizobia. Increased nodule numbers following 3-oxo-C14-HSL
lactone treatment were not under control of autoregulation of
nodulation and were still observed in the autoregulation mutant,
sunn4 (super numeric nodules4). However, increases in nodule
numbers by 3-oxo-C14-HSL were not found in the
ethylene-insensitive sickle mutant. Gene expression analysis
further suggested that
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this AHL affects the expression of ethylene-related genes during
nodulation. It was concluded that plant perception of the S.
meliloti-specific 3-oxo-C14-HSL influences nodule numbers in M.
truncatula via an ethylene-dependent, but
autoregulation-independent mechanism.
A comparison of M. truncatula with M. sativa (alfalfa), Trifolium
repens (white clover) and Lotus japonicus (Lotus) showed that the
observed effects of AHLs on nodule numbers, at least at the
concentration chosen, were specific to M. truncatula, despite M.
sativa nodulating with the same symbiont. In M. truncatula, the
effects of AHLs were specific for an increase in nodule numbers,
but not lateral root numbers or root length. This result suggests
a very specific effect of AHLs on nodulation, possibly via
modulation of ethylene-controlled infection, but not on general
root developmental processes.
During the investigation of protocols to eliminate bacterial
contamination, it was discovered that nodulation phenotypes in
response to AHL exposure strongly depended on the presence of
plant-associated bacteria. Therefore, the composition and
possible role of the M. truncatula-associated microbiome was
further investigated. High throughput sequencing showed that the
antibiotic treatment significantly reduced the presence and
composition of the microbiome. Interestingly, application of
3-oxo-C14-HSL also significantly altered the microbiome, but this
effect was very specific for bacteria belonging to the genus
Pantoea. Only in the absence, but not in the presence of the
majority of the plant microbiome, did M. truncatula show
increased nodulation in response to 3-oxo-C14-HSL, and this was
associated with increased expression of early nodulation genes.
These results suggest that the bacterial community of Medicago
affects nodulation responses towards AHLs, particularly towards
to 3-oxo-C14-HSL, likely by interfering with AHL stability,
perception or plant responses.
In summary, this thesis showed that plant perception of AHLs
alters symbiosis-specific phenotypes, suggesting that AHLs are
not only important to regulate bacterial behaviours during
nodulation, but also that the plant has evolved mechanisms to
respond to specific AHLs from its symbiont, likely by reducing
ethylene signalling or synthesis to enhance the number of
nodules.