The discovery of deep-sea hydrothermal vents caused scientists to reconsider their notions about life in the deep sea. In these seemingly inhospitable environments, free-living microbes, as well as microbial-animal symbioses, thrive in the warm waters around vents. The biomass per unit area in this environment is comparable to that of rainforests. Uniquely, these highly productive ecosystems are based on microbial chemoautotrophic metabolism, wherein microbes generate metabolic energy by drawing oxygen or nitrate from surrounding seawater to oxidize reduced chemicals (e.g., sulfide) found in the vent fluids (Sievert and Vetriani, 2012, in this issue). The rapid and voluminous fluid flux through hydrothermal vents replenishes these substrates at a rate sufficient to support this substantial community. The tremendous microbial productivity observed at vents raises the question as to whether these microorganisms are also well suited for bioenergy and biofuel production. Here, we discuss the utility and issues associated with two example approaches: in situ bioelectricity generation and microbially mediated large-scale biofuel production.

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