Stop showing off and just use the more stable backbone!

Fat-As(s) GFAJ-1 cells high on arsenic. (Wolfe-Simon et. al., 2010)

So you can apparently substitute arsenic for phosphorous^[11]. Yes, we can’t even tell the difference between the two. In our defence, they are both elements of Group 15 and are only very slightly different in electronegativity and size (~0.02 nm). Our enzymes work hard to harvest the little phosphorous we can find and in their enthusiasm, end up being unable to distinguish arsenic from phosphorous. And so, while arsenic is still toxic to us because, for example, it has a high affinity for the dihydrolipoyl groups on our Pyruvate dehydrogenase, you somehow figured out not only how to protect the thiols on your metabolic enzymes from forming crippling chelate complexes with arsenic ions but also how to make the chemical backbones of your macromolecules out of arsenic instead of the universally accepted element, phosphorus. Great job! What do you want us to do about it? Give you a Nobel prize in bio-fucking-chemistry?

But before you go around asking to be knighted, let me bring your attention to a couple of things. I’ll have you know that we have figured out very cool ways to test for arsenic. James Marsh developed the Marsh test in 1836 to test for arsenic poisoning^[8]. (It kills us, you know, and in case you didn’t notice, it was a popular murder tool at the time, which I’m sure you had something to do with.) An italian guy, Bartolomeo Gosio, in 1890, figured out that he could use certain fungi to achieve the volatilization of Arsenous oxide to a garlic-odoured gas on the suspected materials^[1]. He even got this gas, trimethylarsine, named after himself as Gosio gas. Yes, your name starts with a G too but it’s not called GFAJ-1 gas is it? Do I hear you asking if we can tell between arsenic and phosphorous? Well, it turns out we can! How the fuck else do you think peer review works??? NanoSIMS is not only a nicer set of letters than GFAJ, but it is a new kind of secondary ion mass spectrometer that can measure trace elemental concentrations with a resolution of < 50 nm. (These scientists even come up with pop culture reference names for their equipment like MADONNA: MAinz Dust Observatory for the detection of Nanoscale Nuclear Anomalies. Does GFAJ-1 even stand for anything?) This ion microprobe can be used to spatially determine the composition of a material for up to 6 different elements or isotopes^[6]. So not only can we tell our P from our As but we have come a long way in just 300 years and now even use arsenic for the greater good like curing cancer^[9].

And just in case you go around saying “at least I did it without higher conciousness and support of the academy”, let me introduce you to brake fern Pteris vittata which can hyperaccumulate arsenic from the soil. It uses its phosphate transporters in its roots to uptake arsenic ions, reduces arsenate to arsenite if needed and then accumulates the anions primarily in its fronds (up to 27,000 mg As/kg dry weight)^[10]. Ferns may have xylem and phloem (and unlike you, know what fronds are) but don’t even have flowers or seeds! So no, they don’t do it because it’s a challenging academic endeavour. And then there are also these other microbes that are so exclusive that they don’t even bother coming up with douchey acronyms like GFAJ-1. Like Ectothiorhodospira-like and Oscillatoria-like bacteria that can grow by anoxygenic photosynthesis using arsenic(III) as a sole electron donor. These amazing bacteria apparently do not posses a Arsenite oxidase but instead use their Arsenate reductase in reverse to oxidise the oxyanions arsenic(III) to arsenic(V), an electrochemical potential of 139mV^[4]. I hear that they live quite close to you^[5]. How many of your mechanisms to tolerate the toxicity of arsenic did you steal from these hard-working photoautotrophs that have evolved these Arsenate reductase and other arsenic processing genes meticulously from ancient times, long before you even thought about HGT-ing things from them? But you probably already knew about these neighbours and have something to do with why the age of their Arsenate reductase being currently contested by Schoepp-Cothenet et. al.^[7] who you brainwashed with your visions of grandeur or threatened to poisoned with your arsenic backbones.

So, maybe you are an evil alien as some people report. Or maybe just you’re fat because you accumulate the arsenic(V) in your Poly-β-hydroxybutyrate rich vacuole-like regions and have cell body image issues (Figure 1 C/D, Wolfe-Simon et. al., 2010). Either way, stop showing off and just use the more stable and time-tested backbone. Do I need to point out that the symbol for arsenic is As, only one letter away from ASS? CONJUGATE YOU GFAJ-1 ASS!!!!

References

1. Bentley R, Chasteen TG. Microbial methylation of metalloids: arsenic, antimony, and bismuth. Microbiol Mol Biol Rev. 2002 Jun;66(2):250-71.
2. Carter DE, Aposhian HV, Gandolfi AJ. The metabolism of inorganic arsenic oxides, gallium arsenide, and arsine: a toxicochemical review. Toxicol Appl Pharmacol. 2003 Dec 15;193(3):309-34.
3. Henry B.F. Dixon. The Biochemical Action of Arsonic Acids Especially As Phosphate Analogues. Advances in Inorganic Chemistry Volume 44, 1996, Pages 191-227.
4. Kulp TR, Hoeft SE, Asao M, Madigan MT, Hollibaugh JT, Fisher JC, Stolz JF, Culbertson CW, Miller LG, Oremland RS. Arsenic(III) fuels anoxygenic photosynthesis in hot spring biofilms from Mono Lake, California. Science. 2008 Aug 15;321(5891):967-70.
5. Oremland RS, Stolz JF, Hollibaugh JT. The microbial arsenic cycle in Mono Lake, California. FEMS Microbiol Ecol. 2004 Apr 1;48(1):15-27.
6. P. Hoppe. NanoSIMS: A new tool in cosmochemistry . Applied Surface Science. 252 (2006) 7102–7106.
7. Schoepp-Cothenet B, Duval S, Santini JM, Nitschke W. Comment on “Arsenic (III) fuels anoxygenic photosynthesis in hot spring biofilms from Mono Lake, California”. Science. 2009 Jan 30;323(5914):583.
8. Spring RJ. The electrolytic test for detection of arsenic alone and in the presence of other metals. Talanta. 1982 Oct;29(10):883-5.
9. Sumi D, Shinkai Y, Kumagai Y. Signal transduction pathways and transcription factors triggered by arsenic trioxide in leukemia cells. Toxicol Appl Pharmacol. 2010 May 1;244(3):385-92. Epub 2010 Mar 1.
10. Wang J, Zhao FJ, Meharg AA, Raab A, Feldmann J, McGrath SP. Mechanisms of arsenic hyperaccumulation in Pteris vittata. Uptake kinetics, interactions with phosphate, and arsenic speciation. Plant Physiol. 2002 Nov;130(3):1552-61.
11. Wolfe-Simon F, Blum JS, Kulp TR, Gordon GW, Hoeft SE, Pett-Ridge J, Stolz JF, Webb SM, Weber PK, Davies PC, Anbar AD, Oremland RS. A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus. Science. 2010 Dec 2. [Epub ahead of print]