Hydrogenobacter sp. RSW1 Genome sequencing and assembly. Hydrogenobacter sp. RSW1

Aerobic and anaerobic processes tend to be spatially or temporally decoupled at scales ranging from individual cells to ecosystems and from minutes to hours due to bioenergetic considerations, competition, and biochemical incapability with oxygen. Here we describe a metabolically flexible Aquificales bacterium, Hydrogenobacter strain RSW1, isolated from a circumneutral hot spring (68 degrees C) that can oxidize elemental sulfur or hydrogen and can reduce O2 or S0. Cells provided with S0 and O2 produced SO42- and coupled this to growth, while cells provided with H2 and S0 produced sulfide and generated ATP that enhanced cell viability but could not couple this to growth. Surprisingly, the addition of low O2 to cultures grown with H2/S0 stimulated HS- and cell production, indicating simultaneous respiration of S0 and O2. Varying the concentration of H2 and/or O2 impacted whether cells reduced or oxidized S0. Transcripts for proteins involved in H2 oxidation, S0 reduction, and O2 reduction in H2/S0/O2-grown cultures were detected and confirmed co-occurring aerobic and anaerobic respiration while HS- was being produced. Together, these data indicate that RSW1 can simultaneously oxidize H2 and S0 with O2 or simultaneously reduce O2 and S0 with H2. These flexible and hybrid energy metabolisms enhance the growth kinetics of cells and may increase their fitness and competitiveness for energy substrates in their low O2 hot spring habitats. The prevalence of proteins allowing for reduction of S0 in the genomes of thermophilic microaerophiles may suggest these hybrid forms of energy metabolism to be widespread.