Microbial Diversity at the Great Salt Plains of Oklahoma
Mark A. Schneegurt, Ingrid R. Caton, Brooke A. Landon, Sarah L. Castro, Seth A. Perkins
The Great Salt Plains in north-central Oklahoma is a barren 65-km2 salt flat where an evaporite crust of mainly NaCl is maintained with brine from subterranean salt deposits. Salt Plains Microbial Observatory (SPMO) has isolated a wide variety of halotolerant and halophilic bacteria, archaea, cyanobacteria, algae, and fungi. Initial heterotrophic enrichments and plating of SPMO soils yielded 105 diverse aerobic bacteria representing 46 phylotypes. More than a dozen different halophilic archaea and over 200 halotolerant cyanobacteria, diatoms and chlorophyte algae also have been isolated. The culturing campaign is now being extended to organisms that are more specialized and is being supported by culture-independent molecular analyses. Direct DNA extracts from soils have been used to generate 16S rRNA gene libraries. Phylogenetic analyses of the libraries will be compared to previous results of culture isolations from the same soil samples. Examples of many of the organisms important for biogeochemical cycling have not been isolated from or detected in terrestrial hypersaline habitats. Nitrogen fixation activity has been measured and nitrogenase (nifH) gene sequences detected. Clone libraries of nifH genes have been used to identify the numerically dominant diazotrophs. It appears that ammonia oxidizers are present based on PCR amplification of putative amoA gene sequences; however, ammonia-oxidizing bacteria have yet to be isolated. The salt flats are perpetually wet and many areas are clearly anaerobic near the surface. Real-time PCR is being used to detect and count the methanogens and sulfate-reducers in salt plains soils. The relative abundance of bacteria and archaea has been determined as well. This combination of classic microbiology, process-level measurements, and molecular techniques is revealing more of the microbial and functional diversity of the microbial assemblage of the Great Salt Plains. Supported by grants from NSF Microbial Observatories, NIH KINBRE Program of the NCRR, and NSF Graduate Fellows in K-12 Education.