gfaj-1 gfaj-1 gfaj-1 is a strain of rod-shaped bacteria in the family halomonadaceae. it is an extremophile that was isolated from the hypersaline and alkaline mono lake in eastern california by geobiologist felisa wolfe-simon, a nasa research fellow in residence at the us geological survey. in a 2010 science journal publication, the authors claimed that the microbe, when starved of phosphorus, is capable of substituting arsenic for a small percentage of its phosphorus to sustain its growth. immediately after publication, other microbiologists and biochemists expressed doubt about this claim, which was robustly criticized in the scientific community. subsequent independent studies published in 2012 found no detectable arsenate in the dna of gfaj-1, refuted the claim, and demonstrated that gfaj-1 is simply an arsenate-resistant, phosphate-dependent organism. magnified cells of bacterium gfaj-1 grown in medium containing arsenate discovery wolfe-simon at mono lake, 2010 the gfaj-1 bacterium was discovered by geomicrobiologist felisa wolfe-simon, a nasa astrobiology fellow in residence at the us geological survey in menlo park, california. gfaj stands for "give felisa a job". the organism was isolated and cultured beginning in 2009 from samples she and her colleagues collected from sediments at the bottom of mono lake, california, u.s.a. mono lake is hypersaline (about 90 grams/liter) and highly alkaline (ph 9.8). it also has one of the highest natural concentrations of arsenic in the world (200 μm). the discovery was widely publicized on 2 december 2010. taxonomy and phylogeny escherichia coli strain o157:h7 halomonas alkaliphila halomonas venusta strain nbsl13 gfaj-1 halomonas sp. gtw halomonas sp. g27 halomonas sp. dh77 halomonas sp. mp3 halomonas sp. ib-o18 halomonas sp. ml-185 phylogeny of gfaj-1 based on ribosomal dna sequences. molecular analysis based on 16s rrna sequences shows gfaj-1 to be closely related to other moderate halophile ("salt-loving") bacteria of the family halomonadaceae. although the authors produced a cladogram in which the strain is nested among members of halomonas, including h. alkaliphila and h. venusta, they did not explicitly assign the strain to that genus. many bacteria are known to be able to tolerate high levels of arsenic, and to have a proclivity to take it up into their cells. however, gfaj-1 was controversially proposed to go a step further; when starved of phosphorus, it was proposed to instead incorporate arsenic into its metabolites and macromolecules and continue growing. the sequence of the genome of the bacterium gfaj-1 is now posted in genbank. species or strain