Bacterial community composition in hydrothermal plume environments is heterogeneous and distinct

In this work we identified the dominant bacterial populations within the hydrothermal vent plumes of the East Pacific Rise and the Eastern Lau Spreading Center to determine if an endemic population of plume microbes exists, and to establish ecological relationships between microbial populations and vent chemistry. We hypothesize that chemistry and mineralogy play large roles in selecting the bacterial community composition, which is highly variable spatially and temporally in the plume environment. We analyzed samples from hydrothermal vent plumes collected using sediment traps deployed adjacent to two vents at 9°N on the East Pacific Rise (EPR) and with an in situ filtration rosette at the Eastern Lau Spreading Center (ELSC), for bacterial community composition. At the EPR, we examined time series samples from two different vents to assess differences in both time and space using automated rRNA intergenic spacer analysis (ARISA) to identify samples from which we then constructed six clone libraries of the 16S rRNA gene. ARISA indicated that there are separate communities at the two different vents, as well as temporal community differences at each vent. 16S rRNA clone libraries of the EPR plume sediment trap samples are consistent to with the work that has been done previously on plumes, in particular the presence of epsilon-proteobacteria that are indicative of sulfur cycling. There is evidence for iron oxidizing gamma-proteobacteria in some of the plume samples as well. ARISA analysis of plume samples from the ELSC will be presented and compared with the EPR samples. Correlations between chemistry and microbiology will be discussed. We conclude by showing that the plume environment is genetically distinct from the surrounding seawater and represents a deep-sea incubator for microbes that can thrive there. While work to date in hydrothermal environments has focused on determining the microbial communities on active and inactive hydrothermal chimneys and basaltic lavas at and near deep ocean volcanic systems, there is very little comparable data on the plume environment that physically and chemically connects them. This work begins to address that environment.