Abstract
The conversion of cellulosic biomass into biofuels can potentially be improved by employing robust microorganisms and enzymes that efficiently deconstruct plant polysaccharides at elevated temperatures. Many of the geothermal features of Yellowstone National Park (YNP) are surrounded by plant biomass and may support complex microbial communities adapted to utilize plant biomass as a primary carbon and energy source. In this study, a well-known hot spring environment, Obsidian Pool (OP), which is located in the Mud Volcano region of YNP, was examined for potential biomass-active organisms using cultivation independent and enrichment techniques. Of notable interest was a flooded depression adjacent to OP supporting a stand of Juncus tweedyi, a heat-tolerant rush commonly found growing near geothermal features in YNP. Bacterial and archaeal communities in the main pool and vegetated area were studied through 454 pyrosequencing of the 16S rRNA genes. Archaeal diversity in the main pool was higher than bacterial, however in the vegetated area, overall bacterial diversity was significantly higher. DNA isolated from heated sediments surrounding the plants was enriched in members of the Firmicutes including potentially (hemi)cellulolytic bacteria from the genera Clostridium, Anaerobacter, Caloramator and Thermoanaerobacter. Microcosms containing model and real biomass substrates were established at a wide range of temperatures (55oC – 85oC). Microbial activity was observed up to 80oC on all substrates including Avicel, Xylan, switchgrass, and Populus sp. Enrichment cultures revealed some of the most active cellulolytic bacteria, which were not detected in 16S tag libraries.
