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Hydrogen and thiosulfate limits for growth of a thermophilic, autotrophic Desulfurobacterium species from a deep‐sea hydrothermal vent

Stewart, Lucy C., Llewellyn, James G., Butterfield, David A., Lilley, Marvin D., Holden, James F.
Environmental microbiology reports 2016 v.8 no.2 pp. 196-200
hydrogen, hydrogen sulfide, microbial growth, models, nitrates, oxidation, oxygen, pH, pyrite, seawater, sodium chloride, sulfur, temperature, thiosulfates, tube worms, Pacific Ocean
Hydrothermal fluids (341°C and 19°C) were collected < 1 m apart from a black smoker chimney and a tubeworm mound on the Boardwalk edifice at the Endeavour Segment in the northeastern Pacific Ocean to study anaerobic microbial growth in hydrothermal mineral deposits. Geochemical modelling of mixed vent fluid and seawater suggests the mixture was anoxic above 55°C and that low H₂ concentrations (79 μmol kg⁻¹ in end‐member hydrothermal fluid) limit anaerobic hydrogenotrophic growth above this temperature. A thermophilic, hydrogenotrophic sulfur reducer, Desulfurobacterium strain HR11, was isolated from the 19°C fluid raising questions about its H₂‐dependent growth kinetics. Strain HR11 grew at 40–77°C (Tₒₚₜ 72–75°C), pH 5–8.5 (pHₒₚₜ 6–7) and 1–5% (wt vol⁻¹) NaCl (NaClₒₚₜ 3–4%). The highest growth rates occurred when S₂O₃ ²⁻ and S° were reduced to H₂S. Modest growth occurred by NO₃ ⁻ reduction. Monod constants for its growth were Kₛ of 30 μM for H₂ and Kₛ of 20 μM for S₂O₃ ²⁻ with a μₘₐₓ of 2.0 h⁻¹. The minimum H₂ and S₂O₃ ²⁻ concentrations for growth were 3 μM and 5 μM respectively. Possible sources of S₂O₃ ²⁻ and S° are from abiotic dissolved sulfide and pyrite oxidation by O₂.