tag:blogger.com,1999:blog-14072474.post7100960764193292089..comments2023-11-03T06:36:27.305-04:00Comments on Phronesisaical: Arsenic, Phosphorus, Not Such a Big Differencehelmuthttp://www.blogger.com/profile/09069600766378586919noreply@blogger.comBlogger11125tag:blogger.com,1999:blog-14072474.post-84985137987813295332010-12-04T11:24:31.369-05:002010-12-04T11:24:31.369-05:00Excuse me, phosphorus-free diet.Excuse me, phosphorus-free diet.Joelnoreply@blogger.comtag:blogger.com,1999:blog-14072474.post-28043397011349203742010-12-04T11:23:51.075-05:002010-12-04T11:23:51.075-05:00They were able to subsist on an arsenic-free diet ...They were able to subsist on an arsenic-free diet and show a lack of radiolabeled (radioactive) phosphorus incorporation, so the demonstration of arsenic substituion is by inference. I don't have the access to AAAS at home, but it's in the current issue of Science if you want to read the primary literature. Of all the academic journals, Science is probably the most approachable for the layman.Joelnoreply@blogger.comtag:blogger.com,1999:blog-14072474.post-35726572874729742092010-12-04T08:31:30.100-05:002010-12-04T08:31:30.100-05:00More here.<a href="http://phronesisaical.blogspot.com/2010/12/more-on-those-arsenic-eating-bacteria.html" rel="nofollow">More here.</a>Cheryl Roferhttps://www.blogger.com/profile/11082102629165547210noreply@blogger.comtag:blogger.com,1999:blog-14072474.post-36300885961367248342010-12-04T02:00:09.649-05:002010-12-04T02:00:09.649-05:00They found their bacteria in Mono Lake, which, lik...They found their bacteria in Mono Lake, which, like all the (remaining) lakes in the great Basin desert is highly saline. However "merely" ~10,000 years ago, these lakes were not saline. Are the biologists suggesting that the bacteria evolved an arsenic-accepting metabolism during the Holocene? Or are they saying something else???Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-14072474.post-39308963076573951062010-12-03T19:06:48.100-05:002010-12-03T19:06:48.100-05:00Joel, I agree that it's intriguing. But I am w...Joel, I agree that it's intriguing. But I am wondering about some of the questions mt raised, particularly about the DNA. Have all the P's been replaced by As's? That's going to be interesting DNA. Is it reproducing itself normally?<br /><br />And I just like to see credit given for earlier work. Some of the articles sounded like the approach was to substitute As nutrients for all P nutrients. That's entirely analogous to substituting deuterated water for normal water.Cheryl Roferhttps://www.blogger.com/profile/11082102629165547210noreply@blogger.comtag:blogger.com,1999:blog-14072474.post-89155466284858020922010-12-03T18:55:20.370-05:002010-12-03T18:55:20.370-05:00i.e. not much, I'm guessing.i.e. not much, I'm guessing.MThttps://www.blogger.com/profile/02341704109256270557noreply@blogger.comtag:blogger.com,1999:blog-14072474.post-91176769114379581372010-12-03T18:49:56.407-05:002010-12-03T18:49:56.407-05:00I suppose from the astrobiology angle, subbing As ...I suppose from the astrobiology angle, subbing As for P could look like another kettle of fish from subbing D for H, because H is everywhere and D is supposed to predominate nowhere, while arsenic could be abundant where phosphorous isn't, suggesting life could be places we haven't bothered looking...until now. I don't know how much that would matter to the methods with which we've looked so far, or could have looked, if we'd had more respect for arsenic.MThttps://www.blogger.com/profile/02341704109256270557noreply@blogger.comtag:blogger.com,1999:blog-14072474.post-40160629902500345072010-12-03T18:16:13.230-05:002010-12-03T18:16:13.230-05:00Huffington ran it front page on top with a photo f...Huffington ran it front page on top with a photo from space and crediting NASA for discovering a new form of life and I ran to the radio before reading more. Of course NPR had more important things to talk about like FIFA's assignment of the next two World Cups and when I read their gloss on the press release from NASA I wanted to scream. I bookmarked the Daily Beast and hope never to read Huffington again. I'm sure I would have to read 18 column inches of Overbye before I appreciated what's so cool about this, if anything. Does it suggest that no important enzymes act directly on phosphorous atoms, or else their kinetics would be so different targeting arsenic that the bugs would be like mutants or even nonviable? Wait, did the researchers even look for such effects? How do they even know to what extent they've replaced all the P's with As's, and are they really saying it's 100%? I don't care enough to look.MThttps://www.blogger.com/profile/02341704109256270557noreply@blogger.comtag:blogger.com,1999:blog-14072474.post-42169927552495822092010-12-03T16:34:58.764-05:002010-12-03T16:34:58.764-05:00It is true that ingestion of trace minerals can be...It is true that ingestion of trace minerals can be essential to certain enzymatic processes (selenium) or toxic to rapidly growing, potentially cancerous cells (arsenic). However, in no previously demonstrated case has anyone been able to <i>replace</i> one of the six fundamental elements for life with another, non-essential element and still sustain life. <br /><br />Members of the same periodic group share a lot of similarities, but in no way are they the same. This is especially true in biological processes. Sodium and potassium are both critical regulators of membrane potential <i>and</i> fall within the same periodic group, but are in no way biologically interchangable. They are transported through specialized ion channels, have different (often opposing) physiological effects, and have dramatically different pharmacology (injecting sodium chloride, otherwise known as saline, is completely harmless, whereas injected potassium chloride, a component of the lethal injection mixture, will totally kill you).<br /><br />You really have to get into the nitty-gritty of the discovery to see what's so fascinating about it. Phosphorous is an essential component of signal transduction, transcription and translation. Think about it this way; without phosphorous, in every case but this one, there's no DNA. That's a huge advancement in biochemistry, however you slice it.Joelnoreply@blogger.comtag:blogger.com,1999:blog-14072474.post-75706784931200238002010-12-03T07:58:29.665-05:002010-12-03T07:58:29.665-05:00Thanks, Ed. I should have checked the atomic weigh...Thanks, Ed. I should have checked the atomic weights.<br /><br />Totally agree that the addition of electron orbitals makes a bigger difference than the difference between isotopes.Cheryl Roferhttps://www.blogger.com/profile/11082102629165547210noreply@blogger.comtag:blogger.com,1999:blog-14072474.post-38457437147988996912010-12-02T21:06:50.963-05:002010-12-02T21:06:50.963-05:00Neat stuff, Cheryl. But I think that As vs. P has ...Neat stuff, Cheryl. But I think that As vs. P has to be considered a larger change than D vs. H. The atomic weight ratio is about 2 for each pair (slightly larger for As/P) but the AS/P pair has different electron structure, as well.Ed Gaffneyhttp://edgaffney@earthlink.netnoreply@blogger.com