MICROBIAL ECOLOGY OF HYDROGEN-PRODUCING AND HYDROGEN-CONSUMING ANAEROBIC BACTERIA (METHANOGENS, BIOLOGICAL CORROSION, SULFATE REDUCERS)

This thesis deals with several aspects of the microbial ecology of hydrogen-producing and hydrogen-consuming anaerobic bacteria. The problem is put into perspective with an overview of the microbial ecology of anaerobic bacteria. The overview summarizes recent advances in the field which demonstrate that hydrogen plays a central role in the bacterial interactions in anaerobic environments.; Chapter 3 describes two enrichments of bacteria degrading butyrate via interspecific hydrogen transfer. In each enrichment a spore former consumes butyrate in consortia with H(,2)-consuming methanogens. The two enrichments differ in that one grows to an optically dense culture while the second grows in clumps. Microscopic examination suggests that clumping is due to the production of large amounts of extracellular polymer. Several H(,2)-consuming methanogens were identified in the enrichment. It is suggested that attachment of the methanogens to the hydrogen producer allows them to compete for the growth substrate against those bacteria having higher substrate affinity. The isolation of two sporeformers degrading butyrate via obligate proton reduction is doubly significant. First, this is the first report of endospore formers carrying out this type of metabolism. Second, by having spores it becomes easier to try to grow them in pure culture, something not achieved yet for bacteria degrading fatty acids in consortia with methanogens.; Chapter 4 explores the growth strategy of Desulfovibrio vulgaris Madison while growing on choline. It is shown that although the bacterium has the capacity to grow via interspecific hydrogen transfer, or via sulfate reduction, fermentation is the preferred catabolic route. Fermentation can be replaced by electron transport only if fumarate is added as a terminal electron acceptor. The results imply that even though the bacterium has the mechanism to synthesize relatively larger amounts of ATP, it actually utilizes the less efficient one. It is proposed that sulfide could be the cause of the inhibition. It is concluded that this bacterium is an excellent tool for studying the biochemistry of sulfate reduction, in particular for testing recently proposed mechanisms of hydrogen cycling.; In Chapter 5 data are presented providing a new perspective on the role of anaerobic bacteria in anaerobic corrosion. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI...