Hydrogen (H2) has an important role in the anaerobic degradation of organic carbon and is the basis for many syntrophic interactions that commonly occur in microbial communities. Little is known, however, with regard to the biotic and/or abiotic factors that control the distribution and phylogenetic diversity of organisms which produce H2 in microbial communities. In this study, we examined the FeFe-hydrogenase gene (hydA) as a proxy for fermentative bacterial H2 production along physical and chemical gradients in various geothermal springs in Yellowstone National Park (YNP), WY, USA. The distribution of hydA in YNP geothermal springs was constrained by pH to environments co-inhabited by oxygenic phototrophs and to environments predicted to have low inputs of abiotic H2. The individual HydA asssemblages from YNP springs were more closely related when compared with randomly assembled communities, which suggests ecological filtering. Model selection approaches revealed that geographic distance was the best explanatory variable to predict the phylogenetic relatedness of HydA communities. This evinces the dispersal limitation imposed by the geothermal spring environment on HydA phylogenetic diversity even at small spatial scales. pH differences between sites is the second highest ranked explanatory variable of HydA phylogenetic relatedness, which suggests that the ecology related to pH imposes strong phylogenetic niche conservatism. Collectively, these results indicate that pH has imposed strong niche conservatism on fermentative bacteria and that, within a narrow pH realm, YNP springs are dispersal limited with respect to fermentative bacterial communities.
Bibliographical noteFunding Information:
This work was supported by grants from the US Air Force Office of Scientific Research to JWP and JRS and by the NASA Astrobiology Institute (JWP). ESB is graciously supported by a NASA Astrobiology Institute Postdoctoral Fellowship and TLH was supported by a NSF-Integrated Graduate Educational and Research and Training fellowship. We are grateful to Christie Hendrix in the Yellowstone Center for Resources for permitting the research activity and for support in all facets of the research.
Copyright 2011 Elsevier B.V., All rights reserved.
- Yellowstone National Park
- dispersal limitation
- niche conservatism