Properties of Distinct Biofilm Communities at an Acid Mine Drainage Site

The Superfund site at the Richmond Mine in Redding, California contains microorganisms that greatly contribute to the generation of the mine's characteristic acidic, metal-rich environment. Rather than dispersed as single cells, these microorganisms are often found in biofilm communities. Several visually distinct biofilm communities exist in the mine, and they have been previously analyzed by FISH. The different communities are likely to be a reflection of the different microenvironments within the mine. Here, we compare other aspects of these distinct biofilms to better understand how these organisms thrive in their microenvironments. First, we have analyzed the polysaccharides present in the different biofilm samples, since polysaccharides are prominent components of the matrix which holds the biofilms together. Second, we have monitored how resilient the biofilms are to changes in temperature and pH, and to the presence of detergents. Third, since some biofilms have a characteristic pink hue thought to be due to the presence of cytochromes, we have also studied the heme-containing proteins in the pink biofilm samples. And last, we have used ICP-AES, UV-VIS, HRSEM, ATR-FTIR and XRD analyses, to compare the ability of different biofilms to sequester metals including As, Zn, and Fe, which may also have implications in toxicity and metal mobility in water bodies and sediments.