Comparative transcriptomic analysis (nitrate vs. sulfur respiration) in Thermovibrio ammonificans

The reduction of elemental sulfur is an important energy conserving pathway in numerous anoxic geothermal environments. Members of the ubiquitous Epsilonproteobacteria, Aquificae as well as several orders of archaea are all able to conserve energy through sulfur respiration, contributing significantly to sulfur biogeochemical cycling. Despite this, the pathways through which elemental sulfur is reduced to hydrogen sulfide remain unclear in certain cases. Thermovibrio ammonificans is a deep-sea vent thermophilic member the deep-branching family Desulfurobacteriaceae (phylum Aquificae) able to conserve energy from the oxidation of hydrogen and reduction of both nitrate and elemental sulfur. While the pathway through which nitrate reduction to ammonia has been previously identified, the enzymes and pathway involved in sulfur respiration have not. In an effort to elucidate the pathway of sulfur reduction as well as the mechanism used to respire a bulk solid substrate, we performed comparative transcriptomic and proteomic experiments, coupled to microscopy observations.