Actually, I wasn't too clear on this either. Either the article was sloppy or my reading skills are impaired. Well, we have a few rebuttals: It's not an arsenic-based life form : Pharyngula [guest post: Alex Bradley, PhD] Arsenate-based DNA: a big idea with big holes : We Beasties Oddly enough, it seems that a few of my guesses more or less hit the target. Some scientists are guessing that there's a partial incorporation of arsenic into the extremophile's biochemistry and that the low phosphate concentrations in the growth medium might've been enough to fulfill the bacteria's growth requirements. One of the comments in the links posted above had a link to this other article: Microbial Arsenic Metabolism: New Twists on an Old Poison Apparently, another one of my crazy guesses was right. Some extremephiles can indeed use arsenic in anaerobic respiration.
You can't kill a virus with an antibiotic. A virus is a fast replicating nucleic acid. You can kill bacteria and fungi with antibiotics but not viruses. All you can do is stop it from reproducing.
The first article does note that they didn't actually find any specifics, which the NASA press release was light on. "*I've had it pointed out to me that they actually didn't fully demonstrate even this. What they showed was that, in the bacteria raised in arsenates, the proportion of arsenic rose and the proportion of phosphorus fell, which suggests indirectly that there could have been a replacement of the phosphorus by arsenic." This article: [guest post: Alex Bradley, PhD] Arsenate-based DNA: a big idea with big holes : We Beasties shows that I was definitely asking the right questions. To wit: "Once DNA is out of the cell, pure chemical processes take over, and experiments have demonstrated that hydrolysis of arsenate links is fast. So you could do a simple experiment to test whether DNA had a phosphate or arsenate backbone: just remove DNA from the cell and put it in water for a few minutes. Then examine whether it hydrolyzes or not. In an accidental way, Wolfe-Simon et al. performed precisely this experiment. The result indicates that the DNA of GFAJ-1 has a phosphate backbone." I did wonder whether those supposed arsenates were somehow more stable than normal because how could they survive inside the cell in the water in there? "The details are these: to isolate DNA, Wolfe-Simon et al. performed a phenol-chloroform extraction. In this technique, after cellular disruption, DNA and other cellular material were dissolved in water, and then the non-DNA material (such as lipids and proteins) were cleaned out of the mixture using phenol and chloroform. This is a pretty common laboratory procedure, and typically would take an hour or two. But here is the key point: During this whole procedure, the DNA was in water. Remember, proteins were removed from this mixture. Any cellular machinery that stabilized arsenate-DNA was removed. In the absence of biochemistry, pure chemistry takes over: any arsenate-DNA would have been quickly hydrolyzed in the water, breaking down into fragments of small size. Alternatively, phosphate-DNA would not hydrolyze quickly, and large-sized fragments might be recoverable." This was NOT in the NASA release. He also says that in the Sargasso, with epically low phosphate levels, bacteria do remove it from their lipids, but not their DNA. Good calls there. Hopefully this story has legs because the question of "So, how are they protecting these arsenates from hydrolysis?" might be "They aren't, not in DNA anyway.". They better jump on this right away if they want that part of their claim to hold up. Heh, this is funny though. Anti-science people love to think "science" is some giant, monolithic conspiracy where scientists back each other up and cover for each other so their "pet ideas" get put forth. Guess again. The sciences are savage and cutthroat. Look how quickly this claim got jumped on. So now we wait for a rebuttal from Team Arsenic... - Coeloptera
In some ways, science is a lot like fandom; they just have scientific journals instead of LiveJournals. I'm getting a little tired of seeing the "life as we don't know it" claim repeated every time this story is shown somewhere. Even if these lifeforms act as the paper suggests, it's still related to all life on Earth, and isn't evidence of a "shadow biosphere". If it survives scrutiny, it's certainly suggestive that other forms of life are possible. But ultimately this is just an Earth-based lifeform with an adaptation, albeit one we've never seen before. It's times like this, though, I wish I'd been able to clear my schedule to take the astrobiology class my school offered... it probably would have been fascinating stuff.
So while these bacteria are utilizing arsenates in their DNA, it's actually less stable chemically (or so it would appear)? Would this mean the cell was at higher risk of mutation, malfunction, or death during this period? Does that mean that surviving off the environmental arsenic would be more of an ability based in desparation than thriving in a niche? They mentioned that the arsenate-DNA hydrolyzed in water, but did they mean normal water, or the water of the arsenic-rich environment? Would there be any difference in Hydrolysis rates between the two? Or are there definitely cell mechanisms preventing this hydrolysis while the cell is still functional? What the stories are actually saying can get pretty confusing to someone without a biochem background, which I think isn't helping things.
All this does for me is confirm something I've said for the longest time that assuming life cannot exist outside of a planet much like our own is stupid and ignorant, when we only really know how the rules work here and not anywhere else.
Maybe I used the wrong term for whatever it is that makes us sick that mutates to be immune to whatever we take to cure/prevent it. It's really unimportant as to my main point. Whether it be a virus or bacteria makes no difference in the point I was making. Whatever it is that most pro-macro-evolution people throw out there as an example isn't really.
I appreciate the thought, but I get the feeling we'd be the only ones in it. I was just oversimplifying the articles' contents. The growth medium and the native environment merely had extremely low phosphate levels, not nonexistent ones based on what was said. This would just make the extremophile's life difficult but they could cope with it. They're not called extremophile for nothing. Personally, I found the linked article in the comments section the most interesting. It provided an explanation for the incorporation of arsenic into the bacteria's biochemical processes. I've only skimmed it, but it's quite informative. Even if we assume the whole Wolfe-Simon claim is bunk, it's cool to see how some lifeforms can so readily adapt to hostile conditions. The irony is that religious fundamentalists are no different than the hardcore scientists. If you question dogma, they will tear you a new one and feed you to the wolves. It's a slippery slope, though. The whole point of science is to question things and experiment, but most people have this Richard Dawkins douchebag attitude and arrogance. As I recall, we lost about 20 or 30 years of time in cloning advancement because the scientists who did the original cloning experiment on amphibians and failed to achieve comparable results on mammals thought they had the written the alpha and the omega on it...and so did everyone else. Turns out they'd made some mistakes or did some sloppy experimentation and this was only proven when some scientist decided not to follow conventional wisdom and try a similar experiment himself. This. As I said previously, I'm pretty sure nature's more imaginative than humans are. I remember how astronomers and astrophysicists kept saying that Jupiter-sized planets could only exist far away from suns and then, lo and behold, we found a star system where one was zipping around the sun at the same distance as Mercury.
"Hey, yeah, you pointed out the argument I made was wrong, so I totally meant another completely different term (which I can't remember the name of). But rest assured it totally proves I'm right about whatever it is you're talking about." Convincing stuff. You know that there's actually fossil evidence of dolphins and cetaceans developing from terrestrial mammals, right? Ungulids that look kind of like dogs turning gradually into aquatic mammals with fins and stuff. Does that count? And since you're so "pro-science" and pro-hard evidence, how about you provide some published case studies or papers to the contrary in your own thread instead of shitting up every thread about biology into an anti-evolution rant? Because I don't know about the rest of TFW, but I came to this thread to learn about bacteria eating poison, not that.
Well they definitely said they grew more slowly in the arsenic-rich environment with no phosphorus than one with more usual levels of phosphates. So it's got to be a "desperation move". That other article mentioned that we still didn't know for sure that they were using arsenates in their DNA. I am assuming that arsenic content of the water won't effect the extremely fast rate of hydrolysis of arsenates. PHB could do it, as they are stating the vacuoles have. But arsenates in water have 10 minutes or so before they go. Aside from some of the more complex stuff that I can't think of a way to simplify, I like to think I've been speaking layperson for the most part. - Coeloptera
