Laboratory model systems for the study of microbial communities

Olga Sánchez, Isabel Ferrera, Jordi Mas

Research output: Chapter in BookChapterResearchpeer-review

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Abstract

Laboratory cultures have been extensively used in the past as a tool to study the behavior of model organisms subject to a variety of environmental conditions and hence to extrapolate the type of behavior that could be expected from similar microorganisms living in nature. The information obtained using this approach has been crucial for our current understanding of the functional role of certain microbial groups in the environment, but falls short when facing the complexity of interactions operating in real microbial communities. The main drawback associated with the use of laboratory cultures lays on the fact that conditions in such cultures are usually homogeneous and strongly selective. Batch cultures contain initial concentrations of growth substrates much higher than the growthlimiting threshold thus selecting for organisms with very high specific growth rates. Continuous cultures overcome this limitation by forcing the organisms to grow at low substrate concentrations, well within the growth-limiting range. As a result, organisms with a high affinity for the limiting substrate are selected. None of these cases allows the establishment of a complex microbial community. The development of complexity in laboratory reactors requires the existence of a certain degree of heterogeneity, either in time or in space, which allows organisms with different requirements to find their niche and avoid competitive exclusion. In an attempt to provide such heterogeneity we have developed a type of bioreactor where solid surfaces within the reactor allow the structuring of the microbial community in space. Analysis of microbial diversity within the reactor using culture-independent molecular techniques reveals the existence of complex assemblages of bacteria diverse both taxonomically and functionally. While the taxonomic composition of these assemblages seems to vary depending on the origin of the inoculum, the functional composition remains quite constant. The results indicate that the use of relatively simple laboratory reactors incorporating a small degree of heterogeneity allows the development of a significant level of biological complexity and can constitute a valuable tool to study the factors determining microbial diversity in natural environments. © 2008 Nova Science Publishers, Inc. All rights reserved.
Original languageEnglish
Title of host publicationMicrobial Ecology Research Trends
Pages87-114
Number of pages27
Publication statusPublished - 1 Jan 2008

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