Functional and structural responses of a degradative microbial community to substrates with varying degrees of complexity in chemical structure

The objective of the present study was to determine whether cultivation of a degradative community on substrates with varying degrees of chlorination and complexity in chemical structure, as well as cultivation in batch and flow cell culture, would alter the community's functional capability. The community was isolated from oil-contaminated soil and maintained in the laboratory on 2,4,6-trichlorobenzoic acid for 5 months before its ability to grow on 15 different chemicals as sole carbon source was evaluated in batch and flow cell systems. While the community could grow and develop biofilms in flow cells on all the substrates, only 11 of the 15 substrates could support growth in batch culture. Although biofilm development was less extensive on chemicals such as pentachlorophenol (2.09% average area covered by biofilm; average biofilm depth = 3 mu m) than on 2,4,6-trichlorobenzoic acid (50.84% area covered; biofilm depth = 6.4 mu m), no correlation was observed between the degree of chlorination, or number of rings, and the number of planktonic cells or biofilm biomass. In contrast, physicochemical characteristics such as the octanol/water partition coefficient had a significant effect on the development of biofilm biomass. In the case of planktonic communities, the degree of chlorination and ring number also had no effect on the BIOLOG carbon utilization profiles of the resulting communities. Although the sessile communities generally clustered separately from their planktonic counterparts, principal component analysis of carbon utilization profiles of the sessile communities showed different grouping between growth on chlorinated and nonchlorinated substrates. Analysis of the degradative community maintained on 2,4,6-trichlorobenzoic acid over an extended period further showed that adaptation to a new chemical environment is a rather slow process, since the substrate utilization profiles did not stabilize even after 12 months. These results demonstrate the flexibility in metabolic ability and community structure found in microbial communities.