Microbial consortia involved in the anaerobic degradation of hydrocarbons

In this review, we examine the energetics of well-characterized biodegradat ion pathways and explore the possibilities for these to support growth of m ultiple organisms interacting in consortia. The relevant phenotypic and/or phylogenetic characteristics of isolates and consortia mediating hydrocarbo n degradation coupled with different terminal electron-accepting processes (TEAP) are also reviewed. While the information on metabolic pathways has b een gained from the analysis of individual isolates, the energetic framewor k presented here demonstrates that microbial consortia could be readily pos tulated for hydrocarbon degradation coupled to any TEAP. Several specialize d reactions occur within these pathways, and the organisms mediating these are likely to play a key role in defining the hydrocarbon degradation chara cteristics of the community under a given TEAP. Comparing these processes w ithin and between TEAPs reveals biological unity in that divergent phylotyp es display similar degradation mechanisms and biological diversity in that hydrocarbon-degraders closely related as phylotypes differ in the type and variety of hydrocarbon degradation pathways they possess. Analysis of micro cosms and of field samples suggests that we have only begun to reveal the d iversity of organisms mediating anaerobic hydrocarbon degradation. Advancem ents in the understanding of how hydrocarbon-degrading communities function will be significantly affected by the extent to which organisms mediating specialized reactions can be identified, and tools developed to allow their study in situ.