RESUMEN
Life is mostly composed of the elements carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. Although these six elements make up nucleic acids, proteins, and lipids and thus the bulk of living matter, it is theoretically possible that some other elements in the periodic table could serve the same functions. Here, we describe a bacterium, strain GFAJ-1 of the Halomonadaceae, isolated from Mono Lake, California, that is able to substitute arsenic for phosphorus to sustain its growth. Our data show evidence for arsenate in macromolecules that normally contain phosphate, most notably nucleic acids and proteins. Exchange of one of the major bio-elements may have profound evolutionary and geochemical importance.
Asunto(s)
Arseniatos/metabolismo , Arsénico/metabolismo , ADN Bacteriano/química , Halomonadaceae/crecimiento & desarrollo , Halomonadaceae/metabolismo , Fosfatos/metabolismo , Fósforo/metabolismo , Arseniatos/análisis , Arsénico/análisis , Arsénico/química , Proteínas Bacterianas/análisis , Proteínas Bacterianas/metabolismo , California , Medios de Cultivo , ADN Bacteriano/metabolismo , Sedimentos Geológicos/microbiología , Halomonadaceae/citología , Halomonadaceae/aislamiento & purificación , Datos de Secuencia Molecular , Fosfatos/análisis , Fósforo/análisis , Fósforo/química , Espectrometría de Masa de Ion Secundario , Vacuolas/ultraestructura , Microbiología del AguaRESUMEN
Abstract Bovine rumen fluid and slurried hamster feces completely reduced millimolar levels of arsenate to arsenite upon incubation under anoxic conditions. This activity was strongly inhibited by autoclaving or aerobic conditions, and partially inhibited by tungstate or chloramphenicol. The rate of arsenate reduction was faster in feces from a population of arsenate-watered (100 ppm) hamsters compared to a control group watered without arsenate. Using radioisotope methods, arsenate reductase activity in hamster feces was also detected at very low concentrations of added arsenate ( approximately 10 muM). Bacterial cultures were isolated from these materials, as well as from the termite hindgut, that grew using H(2) as their electron donor, acetate as their carbon source, and arsenate as their respiratory electron acceptor. The three cultures aligned phylogenetically either with well-established enteric bacteria, or with an organism associated with feedlot fecal wastes. Because arsenite is transported across the gut epithelium more readily than arsenate, microbial dissimilatory reduction of arsenate in the gut may promote the body's absorption of arsenic and hence potentiate its toxicity.