Saturday, December 18, 2010

Mithradites, he died old

Blessed as we are at Riddled Manor with an over-supply of trivalent and pentavalent arsenic compounds -- entirely due to realgar and orpiment having such really cool names , not to mention being pigments of an unparalleled yellow (and not at all connected with a Mythbusters test of the theory that Napolean was killed by fumes from his arsenic-green wallpaper. Also, don't worry, Christmas Ale is supposed to be that colour), blessed as we are, we were terribly excited by the news about an organism that has seemingly become dependent on arsenic for its metabolism.

The organism in question -- an extremophilic but otherwise bog-standard gammaproteobacterium,* not an Archaebacterium or anything exotic -- had been cultured in the lab with more and more arsenic in the agar medium, and less and less phosphorus, until it evolved a tolerance for the toxin. The researchers reckoned that it was actually using arsenic atoms as substitutes for phosphorus (i.e. with redesigned DNA and RNA chains, and ATAs instead of ATP in its energy economy). Sadly, other researchers have cast nasturtiums on their claim.

Naturally one's immediate thought is to rewrite Strong Poison for the bacterial market. The plot would involve one strain of prokaryote inviting another strain over for dinner, and then (when the dinner guest expires painfully with all the symptoms of acute arsenic poisoning) using the alibi that both diners shared the omelette, with the host remaining unscathed -- so the police should direct their impertinent questions elsewhere. Eventually the only other suspect is cleared when it emerges that the murderer spent many months building up a tolerance for arsenic. All ends happily with conjugation. If the heirs of Dorothy Sayers take exception then they should feel free to kiss my Danish arse.

There is some question as to whether mammalian tetrapods can develop sufficient tolerance for this plot device to work in the Eumetazoan subkingdom. Bergen Evans ridiculed the whole notion of arsenic immunity, though his skepticism was based on the idea sounding silly rather than on any empirical evidence.
Bergen Evans at left

On the other hand, even if you doubt the authority of the N Y Times from 1854,** then I refer you to recent studies from 1906, 1916 and 1945, cited in the Handbook of Pesticide Toxicology. Sadly, no human research; also an unpardonable lack of twin studies. Have I mentioned that Christmas Ale is on the house for readers who happen to have a twin?
On the prehensile tail, chronic exposure to arsenic in the drinking water (liberated into the groundwater by adverse soil chemistry) is apparently a Bad Thing, i.e. carcinogenic and teratogenic. Or so I was informed by a young lady from New York (whom we met on the bus back from walking Tiger Leaping Gorge), who is working in Bangladesh as a sort of public-health residency, encouraging villagers to choose the least arsenical of whatever water supplies are available to them.

Jane resorted to more and more emphatic ways of showing her disapproval of people who used the "On one hand / on the other hand" construction to create the impression of uncommitted neutrality.

I am inclined to cut Ms. Sayers a great deal of slack in this dispute since as well as providing much of my toxicological knowledge, her novels also introduced me to the Kai Lung cycle, and to the poetry of Thomas Lovett Beddoes.

* A member of the Oceanospirillales order, i.e. related to the microbial endosymbiont of the bone-eating snot-worm.

** Citing a Dr Tschudi writing in "a French Medical Journal" and translated by "a writer for the Boston Medical Journal".


Big Bad Bald Bastard said...

I always keep some on hand, in case I have to produce some arsenical bronze.

merc said...

.../I got nothing/.

Substance McGravitas said...

You eat more arsenic, it does less. Stands to reason.

Pass the plutonium please.