Bacterial Variability within an Iron-Silica-Manganese-rich Hydrothermal Mound Located Off-axis at the Cleft Segment, Juan de Fuca Ridge

Terminal-restriction fragment length polymorphisms (T-RFLPs) and traditional clone library analysis were used to identify and assess the spatial variability of microbial communities within an active diffusely venting hydrothermal mound found 4 km off-axis at the Cleft Segment, Juan de Fuca Ridge. T-RFLP fingerprints were generated from three subsamples taken from different depths of a sediment core. The top and center subsamples were dominated by phylotypes clustering with the proposed ζ -Proteobacteria. The bottom of the core was dominated by a phylotype clustering in the Nitrospina group within the δ -Proteobacteria. Cluster analysis of T-RFLP fingerprints from the center of the core shows a similar community structure with those from iron-dominated microbial mat communities collected from NW Eifuku Seamount in the Mariana Island Arc and from Loihi Seamount, Hawaii. Our study demonstrates that off-axis diffuse hydrothermal activity generates microbial communities that can potentially affect their habitat through the differential precipitation of Fe-, Si-, and Mn-rich deposits.