1. Arsenic(III) fuels anoxygenic photosynthesis in hot spring biofilms from Mono Lake, California.
- Author
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Kulp TR, Hoeft SE, Asao M, Madigan MT, Hollibaugh JT, Fisher JC, Stolz JF, Culbertson CW, Miller LG, and Oremland RS
- Subjects
- Anaerobiosis, Arsenate Reductases genetics, Arsenate Reductases metabolism, Autotrophic Processes, California, Cyanobacteria growth & development, Cyanobacteria isolation & purification, Ectothiorhodospira classification, Ectothiorhodospira growth & development, Ectothiorhodospira isolation & purification, Light, Molecular Sequence Data, Oxidation-Reduction, Sulfides metabolism, Arsenates metabolism, Arsenites metabolism, Biofilms growth & development, Cyanobacteria metabolism, Ectothiorhodospira metabolism, Hot Springs microbiology, Photosynthesis
- Abstract
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.
- Published
- 2008
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