Anaerobic environments are distributed over the entire earth and H2 is always present as an intermediate in the decomposition of organic compounds. Under natural conditions, certain anaerobic bacteria capable of H2 consumption, maintain the H2 concentration at threshold levels (1-2 nM for sulfate reducing environments). The physiology of H2 consumption is of interest to environmental microbiologists because of the global significance of this process. However, the ability to study this at the genetic level has only recently emerged. Scientists are now poised to address the question of the mechanism for growth of sulfate reducing bacteria under natural conditions. Desulfovibrio desulfuricans G20 will be used as the model organism. Initial experiments will involve screening a library of 5760 transposon mutants of strain G20 for the ability to grow on H2 together with the benzoate-consuming-H2 producing bacterium Syntrophus aciditrophicus. The screening process uses a modification of the signature tagged mutagenesis procedure. Mutants unable to grow on the H2 produced during syntrophic growth (within the coculture) will be characterized to determine the gene that has been mutated. We predict that we will identify 10-20 functional and regulatory genes in this way. Functional genes will be characterized by comparing the kinetics of H2 consumption among the mutants in order to determine whether these proteins are involved directly in H2 processing. Broader impacts include the use of novel approaches to undergraduate learning. As well, results of these studies could provide useful information to aid in development of biological processes for H2 production or consumption.
