Abstract
BackgroundCommunities of microorganisms control the rates of key biogeochemical cycles, and are important for biotechnology, bioremediation, and industrial microbiological processes. For this reason, we constructed a model microbial community comprised of three species dependent on trophic interactions. The three species microbial community was comprised of Clostridium cellulolyticum, Desulfovibrio vulgaris Hildenborough, and Geobacter sulfurreducens and was grown under continuous culture conditions. Cellobiose served as the carbon and energy source for C. cellulolyticum, whereas D. vulgaris and G. sulfurreducens derived carbon and energy from the metabolic products of cellobiose fermentation and were provided with sulfate and fumarate respectively as electron acceptors.ResultsqPCR monitoring of the culture revealed C. cellulolyticum to be dominant as expected and confirmed the presence of D. vulgaris and G. sulfurreducens. Proposed metabolic modeling of carbon and electron flow of the three-species community indicated that the growth of C. cellulolyticum and D. vulgaris were electron donor limited whereas G. sulfurreducens was electron acceptor limited.ConclusionsThe results demonstrate that C. cellulolyticum, D. vulgaris, and G. sulfurreducens can be grown in coculture in a continuous culture system in which D. vulgaris and G. sulfurreducens are dependent upon the metabolic byproducts of C. cellulolyticum for nutrients. This represents a step towards developing a tractable model ecosystem comprised of members representing the functional groups of a trophic network.
Highlights
Communities of microorganisms control the rates of key biogeochemical cycles, and are important for biotechnology, bioremediation, and industrial microbiological processes
Growth of bacteria in carbon limited continuous-culture systems more closely resembles that in natural ecosystems [13] in contrast to the excess nutrients provided in most microbiological media [13]
Tri-culture inoculation and metabolite monitoring reveals limiting nutrients Two custom built continuous culture vessels as described in the Materials and Methods section and shown in Figure 1 were each inoculated with 50 ml of a previously grown three species community culture comprised of C. cellulolyticum, D. vulgaris, and G. sulfurreducens with cell numbers and ratios similar to those described here as determined by quantitative PCR (qPCR) that was grown under the same continuous flow conditions
Summary
Communities of microorganisms control the rates of key biogeochemical cycles, and are important for biotechnology, bioremediation, and industrial microbiological processes For this reason, we constructed a model microbial community comprised of three species dependent on trophic interactions. While the relatively recent advances in molecular ecology and metagenomic-enabled studies of microbial communities have greatly advanced our understanding of In their natural environments, microbial communities are often growth-limited by the availability of carbon and energy [10,11,12]. The steady-state growth condition afforded by continuous-culture systems is more precise and statistically reproducible than the constantly changing physiological states of cells grown under batch culture conditions [13,14] These approaches may be favored for model community studies
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