A natural view of microbial biodiversity within hot spring cyanobacterial mat communities

This review summarizes a decade of research in which we have used molecular , methods, in conjunction with more traditional approaches, to study hot sp ring cyanobacterial mats as models for understanding principles of microbia l community ecology. Molecular methods reveal that the composition of these communities is grossly oversimplified by microscopic and cultivation metho ds. For example, none of 31 unique 16S rRNA sequences detected in the Octop us Spring mat, Yellowstone National Park, matches that of any prokaryote pr eviously cultivated from geothermal systems; 11 are contributed by genetica lly diverse cyanobacteria, even though a single cyanobacterial species was suspected based on morphologic and culture analysis. By studying the basis for the incongruity between culture and molecular samplings of community co mposition, we are beginning to cultivate isolates whose 16S rRNA sequences are readily detected. By placing the genetic diversity detected in context with the well-defined natural environmental gradients typical of hot spring ma systems, the relationship between gene and species diversity is clarifi ed and ecological patterns gf species occurrence emerge. By combining these ecological patterns with the evolutionary patterns inherently revealed by phylogenetic analysis of gene sequence data, we find that it may be possibl e to understand microbial biodiversity within these systems by using princi ples similar, to those developed by evolutionary ecologists to understand b iodiversity of larger species. We hope that such an approach guides microbi al ecologists to a more realistic and predictive understanding of microbial species occurrence and responsiveness in both natural and disturbed habita ts.