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Artykuły w czasopismach na temat "Bacteria-protozoa food webs"
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Pozzato, L., D. Van Oevelen, L. Moodley, K. Soetaert i J. J. Middelburg. "Sink or link? The bacterial role in benthic carbon cycling in the Arabian Sea's oxygen minimum zone". Biogeosciences 10, nr 11 (2.11.2013): 6879–91. http://dx.doi.org/10.5194/bg-10-6879-2013.
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Abstract. The bacterial loop, the consumption of dissolved organic matter (DOM) by bacteria and subsequent transfer of bacterial carbon to higher trophic levels, plays a prominent role in pelagic food webs. However, its role in sedimentary ecosystems is not well documented. Here we present the results of isotope tracer experiments performed under in situ oxygen conditions in sediments from inside and outside the Arabian Sea's oxygen minimum zone (OMZ) to study the importance of the microbial loop in this setting. Particulate organic matter, added as phytodetritus, was processed by bacteria, protozoa and metazoans, while dissolved organic matter was processed only by bacteria and there was very little, if any, transfer to higher trophic levels within the 7 day experimental period. This lack of significant transfer of bacterial-derived carbon to metazoan consumers indicates that the bacterial loop is rather inefficient, in sediments both inside and outside the OMZ. Moreover, metazoans directly consumed labile particulate organic matter resources and thus competed with bacteria for phytodetritus.
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Pozzato, L., D. Van Oevelen, L. Moodley, K. Soetaert i J. J. Middelburg. "Sink or link? The bacterial role in benthic carbon cycling in the Arabian sea oxygen minimum zone". Biogeosciences Discussions 10, nr 6 (26.06.2013): 10399–428. http://dx.doi.org/10.5194/bgd-10-10399-2013.
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Abstract. The bacterial loop, the consumption of dissolved organic matter (DOM) by bacteria and subsequent transfer of bacterial carbon to higher trophic levels, plays a prominent role in pelagic aquatic food webs. However, its role in sedimentary ecosystems is not well documented. Here we present the results of isotope tracer experiments performed under in situ oxygen conditions in sediments from inside and outside the Arabian Sea Oxygen Minimum Zone (OMZ) to study the importance of the microbial loop in this setting. Particulate organic matter, added as phytodetritus, was processed by bacteria, protozoa and metazoans, while dissolved organic matter was processed only by bacteria and there was very little, if any, transfer to higher trophic levels within the experimental period. This lack of significant transfer of bacterial-derived carbon to metazoan consumers indicates that the bacterial loop is rather inefficient in these sediments. Moreover, metazoans directly consume labile particulate organic matter resources and thus compete with bacteria for phytodetritus.
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Esperschütz, J., A. Pérez-de-Mora, K. Schreiner, G. Welzl, F. Buegger, J. Zeyer, F. Hagedorn, J. C. Munch i M. Schloter. "Microbial food web dynamics along a soil chronosequence of a glacier forefield". Biogeosciences Discussions 8, nr 1 (10.02.2011): 1275–308. http://dx.doi.org/10.5194/bgd-8-1275-2011.
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Abstract. Microbial food webs are critical for efficient nutrient turnover providing the basis for functional and stable ecosystems. However, the successional development of such microbial food webs and their role in "young" ecosystems is unclear. Due to a continuous glacier retreat since the middle of the 19th century, glacier forefields have expanded offering an excellent opportunity to study food web development at differently developed soils. In the present study, litter degradation and the corresponding C fluxes into microbial communities were investigated along the forefield of the Damma glacier (Switzerland). 13C-enriched litter of the pioneering plant Leucanthemopsis alpina (L.) Heywood was incorporated into the soil at sites that have been free from ice for approximately 10, 60, 100 and more than 700 years. The structure and function of microbial communities were identified by 13C analysis of phospholipid fatty acids (PLFA) and phospholipid ether lipids (PLEL). Results showed increasing microbial diversity and biomass, and enhanced proliferation of bacterial groups as ecosystem development progressed. Initially, litter decomposition proceeded faster at the more developed sites, but at the end of the experiment loss of litter mass was similar at all sites, once the more easily-degradable litter fraction was processed. As a result incorporation of 13C into microbial biomass was more evident during the first weeks of litter decomposition. 13C enrichments of both PLEL and PUFA biomarkers following litter incorporation were observed at all sites, suggesting similar microbial foodwebs at all stages of soil development. Nonetheless, the contribution of bacteria and actinomycetes to litter turnover became more pronounced as soil age increased in detriment of archaea, fungi and protozoa, more prominent in recently deglaciated terrain.
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Esperschütz, J., A. Pérez-de-Mora, K. Schreiner, G. Welzl, F. Buegger, J. Zeyer, F. Hagedorn, J. C. Munch i M. Schloter. "Microbial food web dynamics along a soil chronosequence of a glacier forefield". Biogeosciences 8, nr 11 (11.11.2011): 3283–94. http://dx.doi.org/10.5194/bg-8-3283-2011.
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Abstract. Microbial food webs are critical for efficient nutrient turnover providing the basis for functional and stable ecosystems. However, the successional development of such microbial food webs and their role in "young" ecosystems is unclear. Due to a continuous glacier retreat since the middle of the 19th century, glacier forefields have expanded offering an excellent opportunity to study food web dynamics in soils at different developmental stages. In the present study, litter degradation and the corresponding C fluxes into microbial communities were investigated along the forefield of the Damma glacier (Switzerland). 13C-enriched litter of the pioneering plant Leucanthemopsis alpina (L.) Heywood was incorporated into the soil at sites that have been free from ice for approximately 10, 60, 100 and more than 700 years. The structure and function of microbial communities were identified by 13C analysis of phospholipid fatty acids (PLFA) and phospholipid ether lipids (PLEL). Results showed increasing microbial diversity and biomass, and enhanced proliferation of bacterial groups as ecosystem development progressed. Initially, litter decomposition proceeded faster at the more developed sites, but at the end of the experiment loss of litter mass was similar at all sites, once the more easily-degradable litter fraction was processed. As a result incorporation of 13C into microbial biomass was more evident during the first weeks of litter decomposition. 13C enrichments of both PLEL and PLFA biomarkers following litter incorporation were observed at all sites, suggesting similar microbial foodwebs at all stages of soil development. Nonetheless, the contribution of bacteria, especially actinomycetes to litter turnover became more pronounced as soil age increased in detriment of archaea, fungi and protozoa, more prominent in recently deglaciated terrain.
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Eo, Jinu, Kee-Choon Park i Byung-Bae Park. "Short-term effects of organic waste amendments on soil biota: responses of soil food web under eggplant cultivation". Soil Research 50, nr 5 (2012): 436. http://dx.doi.org/10.1071/sr12013.
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The aim of this study was to investigate the effects of reusable organic wastes on soil organisms, with a focus on changes in the soil food web. Bone meal, de-oiled cake, and oyster shell were applied at 5 t ha–1, and the abundance and biomass of soil organisms were measured at 4, 8, and 13 weeks after treatment in soil under eggplant cultivation. The abundance of microflora and fauna was higher in the soils treated with bone meal or de-oiled cake than in untreated soils, suggesting that soil organisms are affected by the quality of applied organic wastes. Increases in the abundance of bacterivorous nematodes were observed under treatment with bone meal or de-oiled cake, but there was little change in the abundance of predatory nematodes. A positive response of microarthropods in the Collembola and Oribatida was apparent, and these organisms are involved as secondary consumers in the soil food web, but the predaceous Gamasida were relatively unaffected. The abundance of protozoa, microbivorous nematodes, Collembola, and Oribatida was correlated with the abundance of bacteria and fungi, indicating that both bacteria- and fungi-based food webs formed. The abundance of the secondary consumers was not significantly correlated with that of the predators. The study suggested that, in the short-term, organic waste alters the primary and secondary consumers but its effect may not extend to predators.
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Laybourn-Parry, Johanna. "Survival mechanisms in Antarctic lakes". Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 357, nr 1423 (29.07.2002): 863–69. http://dx.doi.org/10.1098/rstb.2002.1075.
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In Antarctic lakes, organisms are confronted by continuous low temperatures as well as a poor light climate and nutrient limitation. Such extreme environments support truncated food webs with no fish, few metazoans and a dominance of microbial plankton. The key to success lies in entering the short Antarctic summer with actively growing populations. In many cases, the most successful organisms continue to function throughout the year. The few crustacean zooplankton remain active in the winter months, surviving on endogenous energy reserves and, in some cases, continuing development. Among the Protozoa, mixotrophy is an important nutritional strategy. In the extreme lakes of the McMurdo Dry Valleys, planktonic cryptophytes are forced to sustain a mixotrophic strategy and cannot survive by photosynthesis alone. The dependence on ingesting bacteria varies seasonally and with depth in the water column. In the Vestfold Hills, Pyramimonas , which dominates the plankton of some of the saline lakes, also resorts to mixotrophy, but does become entirely photosynthetic at mid–summer. Mixotrophic ciliates are also common and the entirely photosynthetic ciliate Mesodinium rubrum has a widespread distribution in the saline lakes of the Vestfold Hills, where it attains high concentrations. Bacteria continue to grow all year, showing cycles that appear to be related to the availability of dissolved organic carbon. In saline lakes, bacteria experience sub–zero temperatures for long periods of the year and have developed biochemical adaptations that include anti–freeze proteins, changes in the concentrations of polyunsaturated fatty acids in their membranes and suites of low–temperature enzymes.
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Rochera, Carlos, i Antonio Camacho. "Limnology and Aquatic Microbial Ecology of Byers Peninsula: A Main Freshwater Biodiversity Hotspot in Maritime Antarctica". Diversity 11, nr 10 (21.10.2019): 201. http://dx.doi.org/10.3390/d11100201.
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Here we present a comprehensive review of the diversity revealed by research in limnology and microbial ecology conducted in Byers Peninsula (Livingston Island, South Shetland Islands, Antarctica) during the last two decades. The site constitutes one of the largest ice-free areas within the Antarctic Peninsula region. Since it has a high level of environmental protection, it is less human-impacted compared to other sites within the South Shetland archipelago. The main investigations in Byers Peninsula focused on the physical and chemical limnology of the lakes, ponds, rivers, and wetlands, as well as on the structure of their planktonic and benthic microbial communities, and on the functional ecology of the microbial food webs. Lakes and ponds in Byers range along a productivity gradient that extends from the less productive lakes located upland to the eutrophic coastal lakes. Their planktonic assemblages include viruses, bacteria, a metabolically diverse community of protists (i.e., autotrophs, heterotrophs, and mixotrophs), and a few metazooplankton species. Most of the studies conducted in the site demonstrate the strong influence of the physical environment (i.e., temperature, availability of light, and water) and nutrient availability in structuring these microbial communities. However, top-down biotic processes may occur in summer, when predation by zooplankton can exert a strong influence on the abundance of protists, including flagellates and ciliated protozoa. As a consequence, bacterioplankton could be partly released from the grazing pressure exerted by these protists, and proliferates fueled by external nutrient subsidies from the lake’s catchment. As summer temperatures in this region are slightly above the melting point of water, biotic processes, such as those related to the productivity of lakes during ice-free periods, could become even more relevant as warming induced by climate change progresses. The limnological research carried out at the site proves that Byers Peninsula deserves special attention in the framework of the research in extreme environments. Together with nearby sites, such as Signy Island, Byers Peninsula comprises a featuring element of the Maritime Antarctic region that represents a benchmark area relative to the global distribution and diversity of aquatic microorganisms.
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Dopheide, Andrew, Gavin Lear, Rebecca Stott i Gillian Lewis. "Preferential Feeding by the Ciliates Chilodonella and Tetrahymena spp. and Effects of These Protozoa on Bacterial Biofilm Structure and Composition". Applied and Environmental Microbiology 77, nr 13 (20.05.2011): 4564–72. http://dx.doi.org/10.1128/aem.02421-10.
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ABSTRACTProtozoa are important components of microbial food webs, but protozoan feeding preferences and their effects in the context of bacterial biofilms are not well understood. The feeding interactions of two contrasting ciliates, the free-swimming filter feederTetrahymenasp. and the surface-associated predatorChilodonellasp., were investigated using biofilm-forming bacteria genetically modified to express fluorescent proteins. According to microscopy, both ciliates readily consumed cells from bothPseudomonascostantiniiandSerratiaplymuthicabiofilms. When offered a choice between spatially separated biofilms, each ciliate showed a preference forP. costantiniibiofilms. Experiments with bacterial cell extracts indicated that both ciliates used dissolved chemical cues to locate biofilms.Chilodonellasp. evidently used bacterial chemical cues as a basis for preferential feeding decisions, but it was unclear whetherTetrahymenasp. did also. Confocal microscopy of live biofilms revealed thatTetrahymenasp. had a major impact on biofilm morphology, forming holes and channels throughoutS. plymuthicabiofilms and reducingP. costantiniibiofilms to isolated, grazing-resistant microcolonies. Grazing byChilodonellasp. resulted in the development of less-defined trails throughS. plymuthicabiofilms and causedP. costantiniibiofilms to become homogeneous scatterings of cells. It was not clear whether the observed feeding preferences for spatially separatedP. costantiniibiofilms overS. plymuthicabiofilms resulted in selective targeting ofP. costantiniicells in mixed biofilms. Grazing of mixed biofilms resulted in the depletion of both types of bacteria, withTetrahymenasp. having a larger impact thanChilodonellasp., and effects similar to those seen in grazed single-species biofilms.
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Niedźwiecki, Michał, Malgorzata Adamczuk i Tomasz Mieczan. "Trophic interactions among the heterotrophic components of plankton in man-made peat pools". Journal of Limnology, 20.03.2017. http://dx.doi.org/10.4081/jlimnol.2017.1594.
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<p>Man-made peat pools are permanent freshwater habitats developed due to non-commercial man-made peat extraction. Yet, they have not been widely surveyed in terms of ecosystem functioning, mainly regarding the complexity of heterotrophic components of the plankton. In this study we analysed distribution and trophic interrelations among heterotrophic plankton in man-made peat pools located in different types of peatbogs. We found that peat pools showed extreme differences in environmental conditions that occurred to be important drivers of distribution of microplankton and metazooplankton. Abundance of bacteria and protozoa showed significant differences, whereas metazooplankton was less differentiated in density among peat pools. In all peat pools stress-tolerant species of protozoa and metazoa were dominant. In each peat pool five trophic functional groups were distinguished. The abundance of lower functional trophic groups (bacteria, heterotrophic nanoflagellates (HNF) and ciliates feeding on bacteria and HNF) was weakly influenced by environmental drivers and was highly stable in all peat pool types. Higher fu<span style="text-decoration: underline;">n</span>ctional trophic groups (naupli, omnivorous and carnivorous ciliates, cladocerans, adult copepods and copepodites) were strongly influenced by environmental variables and exhibited lower stability. Our study contributes to comprehensive knowledge of the functioning of peat bogs, as our results have shown that peat pools are characterized by high stability of the lowest trophic levels, which can be crucial for energy transfer and carbon flux through food webs.</p>
Rozprawy doktorskie na temat "Bacteria-protozoa food webs"
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Moreno, Ana Maria Biotechnology & Biomolecular Sciences Faculty of Science UNSW. "Understanding bacteria-protozoa interactions: from grazing resistance mechanisms to carbon flow in bacteria-protozoa food webs". Publisher:University of New South Wales. Biotechnology & Biomolecular Sciences, 2008. http://handle.unsw.edu.au/1959.4/41446.
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Bacteria-protozoa interactions are one of the oldest between prokaryotic and eukaryotic organisms. As such, their study offers a unique opportunity to understand the different relationships that have evolved between them, including pathogenesis, and how their interaction can affect some important processes, such as wastewater treatment. In the first part of the work described here, the grazing defence mechanisms employed by Pseudomonas aeruginosa against the surface grazer, Acanthamoeba castellanii, were investigated. P. aeruginosa cells from early logarithmic growth and stationary phase were found to use different defence strategies. The type-III secretion system (T3SS) was found to be responsible for cytotoxicity of early logarithmic growth cells against A. castellanii. Of the three exotoxins produced by P. aeruginosa PA99, the phospholipase ExoU was found to make the greatest contribution to bacterial toxicity against the amoebae. Interestingly, a PA99null mutant that does not produce any known exotoxins but synthesises a secretion apparatus, was also found to be toxic to the amoeba, suggesting that the T3SS was being used to translocate other unknown toxins. Quorum sensing regulated virulence factor production was found to be involved in the grazing defence response of stationary phase P. aeruginosa cells. A. castellanii was found to be most susceptible to hydrogen cyanide and elastase produced during late logarithmic and stationary phase. In the second part, a stable isotope probing method was developed to investigate carbon flow through bacteria-protozoa food webs in activated sludge. The method was subsequently used to track carbon from bicarbonate and acetate through bacteria-orotozoa food webs under ammonia oxidising and nitrate reducing conditions. It was found that the Peritrich ciliate Campanella umbellaria, dominated the acquisition of carbon from bacteria with access to CO2 under ammonia oxidising conditions. Thus it appears that some of these bacteria must live in the plankton, as C. umbellaria is a filter feeder. No specific protozoan groups were found to dominate carbon acquisition from bacteria with access to acetate, under nitrate reducing conditions, probably due to label dilution. Overall the results presented here showed how bacteria-protozoa interactions have shaped infectious processes in higher eukaryotes, and the dynamics of carbon flow in activated sludge.
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Jackson, Victoria S. "The production and fate of picoplankton and protozoa in the pelagic food web of Napoleon Gulf, Lake Victoria, East Africa". Thesis, Waterloo, Ont. : University of Waterloo, 2004. http://etd.uwaterloo.ca/etd/vsjackso2004.pdf.
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Thesis (Ph.D.)--University of Waterloo, 2004."A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Master of Science in Biology." Includes bibliographical references.
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Thelaus, Johanna. "The aquatic microbial food web and occurence of predation-resistant and potentially pathogenic bacteria, such as Francisella tularensis". Doctoral thesis, Umeå universitet, Ekologi, miljö och geovetenskap, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1620.
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All natural aquatic systems harbour a vast variety of microorganisms. In the aquatic microbial food web, the larger microorganisms (i.e. protozoa) feed on the smaller microorganisms (i.e. bacteria and phytoplankton). An increase in nutrient availability results in changes of the microbial food web structure, like altered community composition and blooms of toxic phytoplankton. In this thesis work I hypothesised that nutrient-rich aquatic environments, with strong protozoan predation, favour the occurrence of predation-resistant bacteria like F. tularensis, and that the microbial food web may provide a reservoir for the bacterium between outbreaks. By using a size-structured ecosystem food web model it was shown that the protozoan predation pressure on bacteria, defined as protozoan predation per bacterial biomass, increases with increasing nutrient availability in aquatic systems (estimated chlorophyll a 0.2 to 112 μg L-1). This dynamics was caused by increasing growth-rate of a relatively constant number of bacterial cells, maintaining the growth of an increasing number of protozoan cells. The results were supported by meta-analysis of field studies. Thus my results suggest that protozoa control the bacterial community by predation in nutrient-rich environments. In a field study in a natural productivity gradient (chlorophyll a 1.4 to 31 μg L-1) it was shown that intense selection pressure from protozoan predators, favours predation-resistant forms of bacteria. Thus, the abundance of predation-resistant bacteria increases with increasing nutrient availability in lakes. Furthermore, I could demonstrate that the bacterium Francisella tularensis, the causative agent of tularemia, was present in eutrophic aquatic systems in an emerging tularemia area. Isolated strains of the bacterium were found to be resistant to protozoan predation. In a microcosm study, using natural lake water, high nutrient availability in combination with high abundance of a small colourless flagellate predator favoured the occurrence of F. tularensis holarctica. In laboratory experiments F. tularensis strains were able to form biofilm at temperatures between 30-37°C, but not below 30°C. In conclusion, I have shown that the protozoan predation pressure on bacteria increases with increasing nutrient availability in aquatic systems. Predation-resistant forms of bacteria, such as F. tularensis are favoured in nutrient-rich environments. The complexity of the microbial food web and nutrient-richness of the water, influence the transmission of the pathogenic F. tularensis holarctica. However, over long periods of time, the bacterium survives in lake water but may lose its virulence. The temperature-regulated biofilm formation by F. tularensis may play a role in colonization of vectors or for colonization of hosts, rather than for survival in aquatic environments.
Książki na temat "Bacteria-protozoa food webs"
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Sirová, Dagmara, Jiří Bárta, Jakub Borovec i Jaroslav Vrba. The Utricularia-associated microbiome: composition, function, and ecology. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198779841.003.0025.
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This chapter reviews current advances regarding plant–microbe interactions in aquatic Utricularia. New findings on the composition and function of trap commensals, based mainly on the advances in molecular methods, are presented in the context of the ecological role of Utricularia-associated microorganisms. Bacteria, fungi, algae, and protozoa colonize the Utricularia trap lumen and form diverse, interactive communities. The involvement of these microbial food webs in the regeneration of nutrients from complex organic matter is explained and their potential contribution to the nutrient acquisition in aquatic Utricularia is discussed. The Utricularia–commensal system is suggested to be a suitable model system for studying plant-microbe and microbe-microbe interactions and related ecological questions.
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Miller, Thomas E., William E. Bradshaw i Christina M. Holzapfel. Pitcher-plant communities as model systems for addressing fundamental questions in ecology and evolution. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198779841.003.0024.
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Carnivorous plants have close associations with other species that live in or on the plant. Sarracenia purpurea has a particularly large number of inquiline species, many of which are obligates that live in its water-filled leaves. These include a well-studied food web of bacteria, protozoa, rotifers, mites, and Diptera larvae, all of which depend on the prey of the host plant. This model system has been used to address fundamental questions in ecology and evolution, including studies of keystone predation, succession, consumer versus resource control, invasion, dispersal, and the roles of resources and predators in metacommunities. The microecosystem also has been used to understand density-dependent selection, the genetic structure of populations, evolution over climatic gradients, and evolution in a multispecies, community context. In this chapter, the ecology of this potentially mutualistic contained community is explored in the context of its carnivorous host.
Części książek na temat "Bacteria-protozoa food webs"
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Juo, Anthony S. R., i Kathrin Franzluebbers. "Soil Biology and Microbiology". W Tropical Soils. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195115987.003.0008.
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Soil organisms are fauna and flora that spend all or part of their life in the soil. They play a vital role in the maintenance of soil fertility through processes such as the accumulation of soil organic matter, soil aggregation, and the mineralization of organic matter which releases nutrients available to higher plants. Moreover, many antibiotics are produced from microorganisms isolated from soils. Soil fauna include macrofauna (> 2 mm in width, such as mice, earthworms, termites, and millipedes), through mesofauna (0.2-2 mm, such as collembola and mites), to microfauna (<0.2 mm, such as nematodes and protozoa). Soil flora include macroflora (such as the roots of higher plants), and microflora (such as algae, fungi, actinomycetes, and bacteria). The activities of soil fauna and flora are intimately related in what ecologists call a food chain or, more accurately, a food web. Higher plants play the role of primary producers by using water and energy from the sun, and carbon from atmospheric carbon dioxide to make organic molecules and living tissues. Soil organisms that eat live plants, such as mice or termites, are called herbivores. Most soil organisms, however, use the debris of dead tissues left by plants and animals (detritus) as their source of food, and are called detritivores. Soil organisms that consume live animals, such as centipedes, mites, spiders, or nematodes, are predators and are called carnivores. Some organisms that live off, but do not consume, other organisms are called parasites. Mycrophytic feeders are organisms that use microflora as their source of food, and include certain collembola, mites, termites, nematodes, and protozoa. The actions of soil fauna in the food web are both physical and chemical, while those of the microflora are mostly biochemical. The actions of mesofauna and macrofauna enhance the activities of the microflora in several ways. First, the chewing action fragments the litter to expose the more easily decomposed cell contents for microbial digestion. Second, the fragmented plant tissues are thoroughly mixed with microorganisms in the animal gut, where conditions are ideal for microbial action. Third, the mobile animals carry microorganisms with them and help them to disperse and find new food sources.