A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus

Abstract

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.

Anion Recognition in Water: Recent Advances from a Supramolecular and Macromolecular Perspective

“…The scientific response to the apparent finding of bacteria (GFAJ‐1) living in an arsenic‐rich, phosphate‐free environment,6 and suggesting the existence of arseno‐DNA, was comprehensive: chemists noted that the rates of hydrolysis50 and reduction51 of arsenate esters would predict a prohibitively low stability for arseno‐DNA; furthermore, biologists showed that trace levels of phosphate were present and sufficient for bacteria,7 and found no detectable arsenic in their DNA 52. It transpired that the bacteria are able to tolerate high arsenate/low phosphate environments because they can be extremely selective in their uptake of the two: a phosphate‐binding protein (PBP) up‐regulated by GFAJ‐1 in phosphate‐poor conditions has a 4500‐fold preference for phosphate over arsenate.…”

“…In 2011, it was reported that a strain of bacteria taken from Mono Lake in California (USA) could grow in media rich in arsenate but free of phosphate 6. Such a result implied that arsenic could replace phosphorus in the bacterial genome, and would be the first instance of life comprised of alternative elements—thus meaning that the search for life outside Earth should be significantly broadened in terms of possible environments.…”

Basic statistical recipes for the emergence of biochemical discernment

“…For example, in eubacteria and eukarya, similar responses to heat stress are mediated by completely unrelated molecules (sigma factor switch or HSF respectively). This relative arbitrariness in the choice of molecules, is also suggested by anecdotic findings such as for example (if confirmed), variant DNA molecules of exotic cells with arsenic instead of phosphate (Wolfe-Simon et al, 2010). Resembling biological structures can also be generated by unrelated machineries, through a phenomenon of convergence driven by physical constraints.…”

De quoi l’extraterrestre est-il le nom ?

“…Ainsi, la vie terrestre est essentiellement composée de carbone, d'hydrogène, d'oxygène et d'azote (avec une pincée de phosphore et de soufre) qui sont aussi quatre éléments chimiques très abondants dans l'univers [8]. Il est donc raisonnable de penser qu'une vie extraterrestre sera aussi basée sur ces éléments, même si une équipe américaine prétend avoir découvert une bactérie utilisant l'arsenic à la place du phosphore [9]. D'autre part, du microorganisme le plus simple à l'organisme le plus complexe, on retrouve un certain nombre de fonctions vitales de base :…”