Academic literature on the topic 'Malleobactin'

ABSTRACT Burkholderia pseudomallei is a gram-negative facultative intracellular pathogen that causes melioidosis, an invasive disease of humans and animals. To address the response of this bacterium to iron-limiting conditions, we first performed a global transcriptional analysis of RNA extracted from bacteria grown under iron-limiting and iron-rich conditions by microarrays. We focused our study on those open reading frames (ORFs) induced under iron limitation, which encoded predicted proteins that could be involved in the biosynthesis and uptake of the siderophore malleobactin. We purified this siderophore and determined that it consisted of at least three compounds with different molecular weights. We demonstrated that ORFs BPSL1776 and BPSL1774, designated mbaA and mbaF, respectively, are involved in the biosynthesis of malleobactin, while BPSL1775, named fmtA, is involved in its transport. These genes are in an operon with two other ORFs (mbaJ and mbaI) whose transcription is under the control of MbaS, a protein that belongs to the extracytoplasmic function sigma factors. Interestingly, the transcription of the mbaA, fmtA, and mbaS genes is not controlled by the availability of the siderophore malleobactin.

Background Burkholderia mallei and Burkholderia pseudomallei are both potential biological threat agents. Melioidosis caused by B. pseudomallei is endemic in Southeast Asia and Northern Australia, while glanders caused by B. mallei infections are rare. Here we studied the proteomes of different B. mallei and B. pseudomallei isolates to determine species specific characteristics. Methods The expressed proteins of 5 B. mallei and 6 B. pseudomallei strains were characterized using liquid chromatography high-resolution tandem mass spectrometry (LC-HRMS/MS). Subsequently, expression of potential resistance and virulence related characteristics were analyzed and compared. Results Proteome analysis can be used for the identification of B. mallei and B. pseudomallei. Both species were identified based on >60 discriminative peptides. Expression of proteins potentially involved in antimicrobial resistance, AmrAB–OprA, BpeAB–OprB, BpeEF–OprC, PenA as well as several other efflux pump related proteins and putative β-lactamases was demonstrated. Despite, the fact that efflux pump BpeAB–OprB was expressed in all isolates, no clear correlation with an antimicrobial phenotype and the efflux-pump could be established. Also consistent with the phenotypes, no amino acid mutations in PenA known to result in β-lactam resistance could be identified. In all studied isolates, the expression of virulence (related) factors Capsule-1 and T2SS was demonstrated. The expression of T6SS-1 was demonstrated in all 6 B. pseudomallei isolates and in 2 of the 5 B. mallei isolates. In all, except one B. pseudomallei isolate, poly-beta-1,6 N-acetyl-D-glucosamine export porin (Pga), important for biofilm formation, was detected, which were absent in the proteomes of B. mallei. Siderophores, iron binding proteins, malleobactin and malleilactone are possibly expressed in both species under standard laboratory growth conditions. Expression of multiple proteins from both the malleobactin and malleilactone polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) clusters was demonstrated in both species. All B. pseudomallei expressed at least seven of the nine proteins of the bactobolin synthase cluster (bactobolin, is a ribosome targeting antibiotic), while only in one B. mallei isolate expression of two proteins of this synthase cluster was identified. Conclusions Analyzing the expressed proteomes revealed differences between B. mallei and B. pseudomallei but also between isolates from the same species. Proteome analysis can be used not only to identify B. mallei and B. pseudomallei but also to characterize the presence of important factors that putatively contribute to the pathogenesis of B. mallei and B. pseudomallei.

AbstractExploiting the symbiotic interaction between crops and nitrogen-fixing bacteria is a simple and ecological method to promote plant growth in prospective extraterrestrial human outposts. In this study, we performed an RNA-seq analysis to investigate the adaptation of the legume symbiont Paraburkholderia phymatum STM815T to simulated microgravity (s0-g) at the transcriptome level. The results revealed a drastic effect on gene expression, with roughly 23% of P. phymatum genes being differentially regulated in s0-g. Among those, 951 genes were upregulated and 858 downregulated in the cells grown in s0-g compared to terrestrial gravity (1 g). Several genes involved in posttranslational modification, protein turnover or chaperones encoding were upregulated in s0-g, while those involved in translation, ribosomal structure and biosynthesis, motility or inorganic ions transport were downregulated. Specifically, the whole phm gene cluster, previously bioinformatically predicted to be involved in the production of a hypothetical malleobactin-like siderophore, phymabactin, was 20-fold downregulated in microgravity. By constructing a mutant strain (ΔphmJK) we confirmed that the phm gene cluster codes for the only siderophore secreted by P. phymatum as assessed by the complete lack of iron chelating activity of the P. phymatum ΔphmJK mutant on chrome azurol S (CAS) agar plates. These results not only provide a deeper understanding of the physiology of symbiotic organisms exposed to space-like conditions, but also increase our knowledge of iron acquisition mechanisms in rhizobia.

A novel Gram-stain-negative, non-motile, spherical-shaped and facultatively anaerobic bacterial strain, designated as GB24T was isolated from bioaerosols of an E-waste dismantling site in Guiyu, Guangdong Province, South PR China. Growth occurred at 15–40 °C (optimum 37 °C), pH 5.5–9.5 (optimum 7.0), and up to 0.5 % NaCl (w/v) under aerobic conditions, GB24T was characterized taxonomically and phylogenetically. The sole isoprenoid quinone detected was ubiquinone-10 (Q-10). The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, three unidentified glycolipids, one unidentified phospholipid, and one unidentified aminolipid. Carotenoid pigments were produced. The major cellular fatty acids (> 10 % of total fatty acids) were C17 : 1ω6c (51.5 %) and summed feature 8 (13.5 %, comprising C18 : 1ω7c and/or C18 : 1ω6c). Phylogenetic analysis based on 16S rRNA gene sequence and draft genome grouped strain GB24T into the genus Roseicella . GB24T was most closely related to Roseicella frigidaeris DB1506T with 97.5 % 16S rRNA gene sequence similarity. The draft genome of GB24T comprised 6 153 170 bp with a DNA G+C content of 71.5 %. The average nucleotide identity (ANI) and in silico DNA–DNA hybridization (isDDH) values between GB24T and DB1506T were 83.2 % (Ortho ANI), 83.3 % [ANI by blast (ANIb)] and 27.0 %, respectively. Further genomic analysis of GB24T revealed the secondary metabolite clusters of terpene and phosphonate, which indicate the capacity for malleobactin (14 %) and phosphinothricin (6 %) tripeptide production. On the basis of the genotypic, chemotaxonomic and phenotypic results, GB24T represents a novel species, for which the name Roseicella aerolata sp. nov. is proposed. The type strain of Roseicella aerolata is GB24T (= GDMCC 1.2169T = JCM 34449T).

Dans les régions tempérées, les minéraux et les roches représentent la source principale de cations nutritifs des sols des écosystèmes à faible intrants telles que les forêts. Dans de tels environnements pauvres en nutriments, l’accès et le recyclage des cations nutritifs sont des processus clés pour la croissance et la productivité des arbres. Cependant, ces cations nutritifs ne sont pas directement accessibles aux racines des arbres car piégés dans les minéraux et roches des sols. En conséquence, le processus d’altération des minéraux joue un rôle essentiel car il contribue à restaurer la fertilité des sols et à fournir des nutriments inorganiques nécessaires à la croissance des arbres. L’altération des minéraux peut être dûe à des processus abiotiques (pH, érosion…) ou des processus biotiques (plantes, champignons, bactéries…). Parmi les acteurs biotiques, les bactéries sont capables d’altérer les minéraux par différents mécanismes comme la production de protons (acidolyse) ou la production de molécules chélatrices (complexolyse). Néanmoins, les gènes et protéines impliqués dans l’altération des minéraux par les bactéries sont mal connus. Dans le cadre de cette thèse, la souche bactérienne Collimonas pratensis PMB3(1) a été utilisée comme modèle pour identifier les gènes de l’altération. Cette souche a été isolée de la mycorhizosphère du chêne et est particulièrement efficace pour altérer les minéraux. Dans cette thèse l’analyse du génome de la souche PMB3(1) a mis en évidence l’absence certains gènes décrits dans l’altération (comme les glucose déshydrogénases PQQ dépendantes) et a souligné la nécessité de développer deux approches complémentaires : avec et sans a priori. (i) La démarche sans a priori a été développée via la création d’une banque de mutants aléatoires. Le criblage de cette banque de mutants sur des biotests mimant l’altération des minéraux a permis de sélectionner 3 mutants impactés dans leur capacité à altérer les minéraux. La caractérisation de ces mutants a révélé des mutations dans différents gènes impliqués dans la synthèse d’une glucose/méthanol/choline oxidoréductase (GMC). La comparaison de composés chimiques présents dans le surnageant de la souche sauvage et des mutants a révélé que cette GMC était responsable de la métabolisation du glucose en gluconate et de la production de protons, conduisant à une acidification du milieu et à une acidolyse des minéraux. (ii) La démarche avec a priori a été réalisée par la création d’un mutant ciblé au niveau du gène mbaA codant pour un NRPS (Non-Ribosomal Peptide Synthetase) responsable de la synthèse de sidérophore. L’utilisation conjointe de méthodes de chromatographie et de spectrométrie de masse a permis de caractériser chimiquement ce sidérophore, qui a été identifié comme étant une malléobactine. La comparaison de la souche sauvage et du mutant a révélé que la production de la malléobactine est impliquée dans l’altération de l’hématite par complexolyse et ce dans un milieu avec un fort pouvoir tampon. Les tests d’altération réalisés avec différents types de minéraux en présence de deux sources de carbones (glucose ou mannitol) et deux milieux ayant un pouvoir tampon différent ont révélé que la souche PMB3(1) était efficace pour altérer tous les minéraux testés. De plus, la source de carbone et le tampon du milieu avaient une forte influence sur l’efficacité des agents altérants. Enfin, des résultats préliminaires ont été obtenus sur la régulation des gènes et protéines en fonction de la disponibilité en nutriments inorganiques et de la présence du minéral par des techniques de transcriptomique et protéomique. Pour conclure, cette thèse a permis de (i) découvrir de nouveaux gènes liés à l’altération des minéraux par les bactéries, (ii) mettre en évidence l’influence des facteurs environnementaux dans l’efficacité des mécanismes d’altération utilisés par les bactéries
In temperate regions, minerals and rocks represent one of the main sources of nutritive cations in the soil of low-input ecosystems such as forests. In such nutrient-poor and non-amended environments, the access and the recycling of nutritive cations are key processes for tree growth and productivity. However, these nutritive cations are almost inaccessible to the tree roots as they are entrapped into organic matter or into soil minerals and rocks. Consequently, the mineral weathering process is essential, as it allows the restauration of soil fertility and provides the inorganic nutrients for tree growth. Mineral weathering can be attributed to abiotic (temperature, pH, erosion…) or biotic (plants, fungi, bacteria…) processes. Among the biotic processes, bacteria are able to weather minerals by different mechanisms such as the production of protons (acidolysis) or the production of chelating molecules (complexolysis). However, genes and proteins involved in mineral weathering by bacteria are not yet elucidated. As part of this thesis, a bacterial Collimonas pratensis strain PMB3(1) was used as a model to identify genes involved in mineral weathering. This strain was isolated from oak mycorrhizosphere and is efficient in weathering minerals. In this thesis, the analysis of the genome of the strain PMB3(1) evidenced the absence of certain genes described in mineral weathering (such as PQQ-dependent glucose dehydrogenases) and highlighted the need to develop two complementary approaches: with and without a priori. (i) The without a priori approach, has been developed with the building of a mutant library with the insertion of a plasposon pOT-182. The screening of this mutant library on biotests miming mineral weathering allowed the selection of three mutants impacted in their mineral weathering ability. The characterisation of these mutants revealed mutations in different genes involved in a glucose/methanol/choline oxidoreductase (GMC) synthesis. Comparisons between wild type and mutants chemical compounds in the culture supernatants showed that this GMC was able to converts glucose to gluconate and produce protons, leading to the acidification of the medium and minerals acidolysis. (ii) The with a priori approach was the building of a mbaA mutant coding for a NRPS (non-ribosomal peptide synthetase) responsible of siderophore biosynthesis. The combined use of chromatography (HPLC) and mass spectrometry (LC-ESI-MS and MS/MS) methods allowed to chemically characterize the siderophore as malleobactin X. Comparisons between wild ype and mbaA mutant strains revealed that the production of malleobactin was involved in mineral weathering by complexolysis in a strong buffered medium. Weathering tests performed with different mineral types in presence of two carbon sources (glucose or mannitol) and two media with different buffering capacities showed that the strain PMB3(1) was efficient to weather all tested minerals and that weathering molecules (GMC and malleobactin) had a similar effect whatever the mineral type. Furthermore, the carbon source and the buffering capacity had a strong influence on weathering molecules efficiency. Finally, preliminary results have been obtained on the regulation of genes and proteins according to inorganic nutrients availability and the presence of minerals by transcriptomic and proteomic technics. To conclude, this thesis (i) allowed the discovery of new genes involved in mineral weathering by bacteria, (ii) evidenced the influence of environmental factors in efficiency of molecular mechanisms involved in mineral weathering and used by bacteria