Mineral Separation for Discerning Microbe-Mineral Interactions (graduate student Ben Harrison)Cells have been shown to differentially attach to minerals of variable structure and composition in diverse environments. In some cases this results from the properties of the cell wall of the mineral surface. Alternatively, cells may preferentially colonize mineral surfaces which afford them key nutrients or electron donors/acceptors for respiration. We have been developing methods separating mineral fractions of environmental samples using an applied magnetic field or heavy liquids in order to characterize their associated microbial communities with molecular techniques (e.g. DNA extraction with 16S rRNA gene amplification followed by clone library construction or TRFLP, fluorescent in situ hybridization). This approach is particularly well suited to marine sediments, in which microbe-mineral interactions are poorly constrained.
We have applied this approach to hydrothermal chimneys of the Lau and North Fiji Backarc basins in the Western Pacific as well as continental margin sediments off California. These methods are also playing a role in characterizing novel microbial communities in oxic, deep-ocean red clays of the South Pacific Gyre. Such open-ocean environments have received little microbiological study The extreme nutrient limitation encountered in these sediments, derived from poor availability of organic matter descending from the water column, may encourage composition-dependent patterns of microbial mineral colonization.