CYANOBACTERIA, UNEXPECTED MICROBES IN ACID MINE DRAINAGE

Our discovery of cyanobacteria growing in acid conditions has important repercussions for the geomicrobiology of acidic systems since acid conditions are known to preclude cyanobacteria. A biomarker unique to cyanobacteria (mid-methyl branched fatty acid (9-Me-15:0)) was recently discovered in stromatolitic Fe-rich deposits in an acid mine drainage (AMD) system at the abandoned Green Valley coal mine site (GVS) in western Indiana. In this study, we searched for and discovered cyanobacteria living in eukaryote-dominated biofilms, which are known to contribute to the formation of Fe-rich stromatolites at this site. During sampling, AMD pH was ranged from 2.7 to 3.5 depending on weather conditions. Eukaryotic dominated biofilms consisted primarily of the photosynthetic acidophilic protozoan Euglena mutabilis. In this study cyanobacteria were isolated by streaking biofilm material on plates containing BG11 medium. Resulting colonies were sub-cultured. All cultures were grown aerobically under lights. To date, representative species of at least three genera, including Nostoc and Oscillatoria, have been identified. Identification of other cyanobacterial isolates will be presented. Preliminary analysis of fatty acid biomarkers in these isolated species revealed that at least two species contain 9-Me-15:0. We expect that additional fatty acids will be identified from our other cyanobacterial isolates. Future research will focus on the ecological significance of this unique microbial component of the eukaryote-dominated biofilm.