The use of multiple-vessel,open flow systems to investigate carbon flow in anaerobic microbial communities

Five vessels, connected in series, were used for a continuous flow system to model carbon flow in anaerobic microbial communities. Two such 5-vessel systems were constructed, the inflows containing 10 mM sulfate and either 10 mM glucose or benzoate. Dilution was slow (D=0.0018 h^?1 for the whole system). Analyses of dissolved organic and inorganic carbon, and of CO₂ and CH₄, showed that the systems attained steady states in which biomass was constant, although there was net biosynthesis in the early vessels and net mineralization in succeeding vessels. Examination of the distributions of sulfate reduction, methanogenesis, and of H₂+CO₂-utilizing fatty acid-forming bacteria revealed spatial separation of these functional groups of bacteria in different vessels of the array, resembling the vertical spatial separation found in many natural sediments. Such model systems should, therefore, prove valuable in investigating the many microbial activities that contribute to the flow of carbon in anaerobic microbial communities.