Arsenic(III) Fuels Anoxygenic Photosynthesis in Hot Spring Biofilms from Mono Lake, California

• Published in: Science (American Association for the Advancement of Science) 2008-08, Vol.321 (5891), p.967-970
• Main Authors: Kulp, T.R, Hoeft, S.E, Asao, M, Madigan, M.T, Hollibaugh, J.T, Fisher, J.C, Stolz, J.F, Culbertson, C.W, Miller, L.G, Oremland, R.S
• Format: Article
• Language: English
• Subjects: Anaerobiosis; Animal, plant and microbial ecology; Arsenate Reductases - genetics; Arsenate Reductases - metabolism; Arsenates - metabolism; Arsenic; Arsenites; Arsenites - metabolism; Autotrophic Processes; Bacteriology; Biofilms; Biofilms - growth & development; Biological and medical sciences; California; Cyanobacteria; Cyanobacteria - growth & development; Cyanobacteria - isolation & purification; Cyanobacteria - metabolism; Cyanophyta; Ectothiorhodospira; Ectothiorhodospira - classification; Ectothiorhodospira - growth & development; Ectothiorhodospira - isolation & purification; Ectothiorhodospira - metabolism; Electrons; Freshwater; Fundamental and applied biological sciences. Psychology; Genetics; Hot springs; Hot Springs - microbiology; Light; Metabolism; Metabolism. Enzymes; Microbial ecology; Microbiology; Molecular Sequence Data; Oxidation; Oxidation-Reduction; Photosynthesis; Sulfides; Sulfides - metabolism; Various environments (extraatmospheric space, air, water)
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1160799

Phylogenetic analysis indicates that microbial arsenic metabolism is ancient and probably extends back to the primordial Earth. In microbial biofilms growing on the rock surfaces of anoxic brine pools fed by hot springs containing arsenite and sulfide at high concentrations, we discovered light-dependent oxidation of arsenite [As(III)] to arsenate [As(V)] occurring under anoxic conditions. The communities were composed primarily of Ectothiorhodospira-like purple bacteria or Oscillatoria-like cyanobacteria. A pure culture of a photosynthetic bacterium grew as a photoautotroph when As(III) was used as the sole photosynthetic electron donor. The strain contained genes encoding a putative As(V) reductase but no detectable homologs of the As(III) oxidase genes of aerobic chemolithotrophs, suggesting a reverse functionality for the reductase. Production of As(V) by anoxygenic photosynthesis probably opened niches for primordial Earth's first As(V)-respiring prokaryotes.