Chemoautotrophy: Discerning the Key Perpetrators from the Cariaco Redoxcline Lineup of Suspects

Our polyphasic investigation was designed to characterize microbial communities and metabolic activities across the well-constrained Cariaco Basin redoxcline. We coupled interrogations of microbial functional potential (metagenomics), activity (rate measurements and gene expression), and taxonomic diversity (based on SSU rRNA) to identify the key suspects in chemoautotrophic processes. We infer from these data the microbial impacts on key ecological/geochemical processes. Contrary to popular belief and former testimonials, the epsilon-proteobacteria are not the sole perpetrators, and the gamma-proteobacteria are currently the main suspects. Sulfur oxidation appears to be the main source of energy production and Marine Group A and delta-proteobacteria are implicated as partners in crime regarding cryptic sulfur cycling. Anammox bacteria play a key role in the micro-oxic water layers. Data suggest that even the permanently-stratified Cariaco basin is not a static ecosystem, but instead, one that experiences temporal and spatial perturbations and evolution.