Hydrogen Thresholds and Steady-State Concentrations Associated with Microbial Arsenate Respiration

• Published in: Environmental science & technology 2007-04, Vol.41 (7), p.2311-2317
• Main Authors: Heimann, Axel C, Blodau, Christian, Postma, Dieke, Larsen, Flemming, Viet, Pham H, Nhan, Pham Q, Jessen, Søren, Duc, Mai T, Hue, Nguyen T. M, Jakobsen, Rasmus
• Format: Article
• Language: English
• Subjects: Arsenates - metabolism; Arsenic; Arsenic content; Bacteriology; Biodegradation, Environmental; Biological and medical sciences; Chemical reactions; Chromatography, Gas; Contamination; Electrons; Environmental Pollutants - metabolism; Epsilonproteobacteria - metabolism; Fundamental and applied biological sciences. Psychology; Geologic Sediments - analysis; Hydrogen - metabolism; Metabolism. Enzymes; Methane - metabolism; Microbiology; Microorganisms; Respiration; Sediments; Thermodynamics; Vietnam
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es062067d

H2 thresholds for microbial respiration of arsenate (As(V)) were investigated in a pure culture of Sulfurospirillum arsenophilum. H2 was consumed to threshold concentrations of 0.03−0.09 nmol/L with As(V) as terminal electron acceptor, allowing for a Gibbs free-energy yield of 36−41 kJ per mol of reaction. These thresholds are among the lowest measured for anaerobic respirers and fall into the range of denitrifiers or Fe(III)-reducers. In sediments from an arsenic-contaminated aquifer in the Red River flood plain, Vietnam, H2 levels decreased to 0.4−2 nmol/L when As(V) was added under anoxic conditions. When As(V) was depleted, H2 concentrations rebounded by a factor of 10, a level similar to that observed in arsenic-free controls. The sediment-associated microbial population completely reduced millimolar levels of As(V) to arsenite (As(III)) within a few days. The rate of As(V)-reduction was essentially the same in sediments amended with a pure culture of S. arsenophilum. These findings together with a review of observed H2 threshold and steady-state values suggest that microbial As(V)-respirers have a competitive advantage over several other anaerobic respirers through their ability to thrive at low H2 levels.