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Bacterium isolated from California's Mono Lake has arsenic in its DNA
Posted by Uwe Kolitsch
Uwe Kolitsch December 04, 2010 04:49PMhttp://www.scientificamerican.com/article.cfm?id=arsenic-life
Rob Woodside December 04, 2010 07:02PMAs undergrads my friend, a biologist, grew saltwater tolerant copopods from fresh water copopods by simply adding salt and breeding the survivors. Now Mono lake has produced arsenic tolerant bugs by feeding them arsenic and not much phosphorus. The exciting thing here is the possibility of an Arsenic eating bacterium that might sequester Arsenic from ground water etc. I'm not sure how to filter out the bacterium to actually remove or mine the Arsenic, but it is interesting. Also interesting are the structural and biochemical changes that result from breeding tolerant strains. However this is a long way from Arsenic based aliens as adverstised by NASA!!! This is very reminiscent of the Martian life that NASA found in an Antarctic meteorite which they announced with great fanfare. The immediate refutations somehow didn't get the same treatment. It is sad when NASA has to resort to such showboating hoping to get funding from the bright lights in the US congress.
Knut Eldjarn December 04, 2010 08:44PMRob, there seems to be more to the story than just arsenic tolerant bacteria, but still far away from an alternative form of life. Replacing Carbon with Silicium and Phosphorus with Arsenic - breathing Sulphur instead of Oxygen - that would be something. I think NASA will have to come up with something more than the Mono lake bacteria to atract serious funding for sci-fi adventures in the present financial climate. But every new bit of information about the diversity of the chemistry in living organisms is always fascinating.
I nice weekend to you all.
Rob Woodside December 05, 2010 12:07AMKnut, I'm not sure there is any more to it. The dream seems to be that no longer does life necessarily depend on only 6 elements but that one of them, phosphorus, can be entirely replaced by arsenic. First of all life depends on a lot more than 6 elements. Second, in spite of mimetite and pyromorphite, phosphorus and arsenic will not always produce identical structures, let alone "life forms". Already there are visible differences between the Arsenic tolerant and parent bugs. It will be interesting to see just how far the substitution can go but I doubt very much there will be an Arsenic end member.
In these bankrupt times of budget and revenue cutting mania, NASA could do both by cutting its manned space program which has gone nowhere in the last generation and spend more on its robot programs that have been a well spring of discovery and could sorely use the cash.
Edited 1 time(s). Last edit at 12/05/2010 12:16AM by Rob Woodside.
Ray Hill December 05, 2010 12:44AMI felt that the gist of the message was that we need to constantly review what it is that we define as life, and that this had knocked
one more level off the list of things requiring a definition for life...
yes there are already uniquely based life forms at the vents on the deep sea
floor, and they were the first really big divergences from our basically carbon based life form definition, but I happen to welcome anything that
will bring attention back to the search for other life in the universe, and that broadens our definitions so that we don't actually miss it , when we find it...and of course, keeps the money coming into the space program...and yes Rob, the roboticized remote program is amazing, but it's limitations will eventually push us, if we keep the programs funded, to eventually sending man out there to do a more detailed and flexible research and search on the near planets....
Rob Woodside December 05, 2010 01:02AMIn the immortal words of Patrick Suppes, " Man is a meat machine and what a meat machine can do, a metal machine can do!"
Now that we've tested the waters by going to the moon, I don't think we should be wasting time and money on manned programs until we can cheaply and reliably orbit Mega ton containers. I'm surprised that the Apollo astronauts aren't all dying from cancer due to their solar wind and cosmic ray exposures.
Norman King December 05, 2010 01:36AM" . . . in spite of mimetite and pyromorphite, phosphorus and arsenic will not always produce identical structures, let alone "life forms". Already there are visible differences between the Arsenic tolerant and parent bugs." (Rob Woodside)
This is the essence of natural selection. I love it, and I'll pay for more research!
Then, maybe from little bits and scraps of knowledge such as this, we'll someday learn the full scope of life and its evolution.
Harris Mason December 05, 2010 03:30AMI think there is a some misunderstanding of the research presented above. Yes, life depends on more than just 6 elements (Cu, and Cr are toxic in large amounts but needed in small amounts for some enzymes to function), but traditional thinking has been that these 6 elements absolutely have to be present since they are the major components to proteins, DNA, ATP, etc. P is absolutely needed to make DNA and ATP and without these you are dead. Here though they grew the bacteria in the complete absence of P. So they cannot synthesize these "essential" compounds. Instead they inoculate the growth media with As and the bacteria (while not growing as easily in the P media) still lived and multiplied. Therefore, they must be using AsO4 in analogues of these critical compounds (they had no P to make it otherwise!). The mere finding that this bacteria can grow in the presence of As alone makes scientists have to rethink what is commonly considered "necessary" for life. This is completely different from a resistance.
Rob you are right they are likely going to have different structures If they had the same structure as our DNA and ATP we could do the same thing, but no one is going to start using arsenates as food preservatives anytime soon. I am sure this will unleash a flurry of research into what the structure of these compounds are, and how the organisms synthesize them.
Also the suggestion that this a waste of NASA funds illustrates a lack of understanding of how much money is allocated for this kind of research. The astrobiology funds are so minor compared to the total NASA budget. And yes NASA is going to play it up for the press. They should! This is cool research and they should be proud of the results. Evolution is amazing!
Norman King December 05, 2010 04:03PMIn view of the current interest in Mono Lake and the interesting life forms just reportred from there, I have uploaded (in "New Photos Today") a sort of photo essay on Mono Lake--primarily about the tufa deposits. I haven't researched the occurrence of those life forms, but there were many comments already in the on-line material about communities of bacteria and other microbes living in the tufa, and perhaps even mediating its precipitation. I took all of the photos in July of 2003. Enjoy!
Edited 1 time(s). Last edit at 12/05/2010 06:29PM by Norman King.
Henry Barwood December 05, 2010 05:29PMMakes me wonder what other metals bacteria may utilize, and their relationship to ore bodies and supergene weathering. Transfer of metals inside the bacteria instead of the bacteria simply altering the local conditions to cause precipitation and concentration of ores.
Troy, Alabama USA
Rob Woodside December 05, 2010 07:16PMSo far we appear to have garbled press accounts with lots of spin. Some say "As is in the DNA", others say "if confirmed". Some say "P poor environment" , others "no P whatsoever", etc. We will probably have to await the published results to know just what has been done. As an ignorant physicist it never occurred to me that there were only 6 elements absolutely required for life. From people's reactions I suppose this idea rates with sunlight or water being absolutely necessary for life. I can only hope that these As tolerant bugs will turn out to be as fascinating and fruitful as the black smoker colonies, etc.. The cost of this research is peanuts compared to the manned space program and I'm not advocating cutting this. If the manned space boondoggle was shut down NASA would have more money to spend on interesting work like this and robotic missions.
Knut Eldjarn December 05, 2010 07:51PMThey way a large number of metals and other elements are incorporated in biomolecules and used in different life processes is a very important field of research (metalonomics etc). While only a 6 elements are considered major elements in living organisms, it is clear from recent studies that a much larger number of elements may have yet undiscovered vital functions in trace amounts. Studies depriving pregnant goats of a large number of unusual elements one by one have shown grave interferences in fetal development indicating that the first living organism on earth made use of a much larger part of the periodic system than most people know. Such findings may have important implications both for nutrition and new drugs. Exposure to small amounts of other elements over a long period of time may also have unknown detrimental effect on living organisms. The way we treat this planet, our long term survival may depend on a far better understanding of the total interaction between living organisms and the inorganic environment. Any new contribution in this field, like the studies of the Mono lake bacterias can turn out to be of great importance.
Edited 1 time(s). Last edit at 12/06/2010 09:20AM by Knut Eldjarn.
Peter Haas December 07, 2010 05:43AM
That possibility looks more promising in the light of a new study describing a bacterium isolated from California's Mono Lake that can use arsenic, which is usually poisonous to life, as one of its key nutrient elements. The microbe can even take up arsenic into its biomolecules, replacing phosphorus as a structural building block in DNA and possibly in energy-carrying molecules such as adenosine triphosphate (ATP) as well.
(1) Replacement of phosphate units with arsenate units in biomolecules is not new. There has been research on this topic in the past. If there is a high enough concentration of arsenate offered, it will be inevitably incorporated in biomolecules. The reason for this is simply an equilibrium effect. Phosphate and arsenate are structural analogues and undergo the same reactions. There are only quantitative differences, i.e. the reactivities are not the same.
(2) Whether the arsenic analogues are still functional is a completely different question. In this respect, the bare fact of their existence does mean nothing. There is essentially no basis for the conclusion that "we have a new element in the group of six that, at least for this organism, can sustain life", which is presented later in the article. One may conclude that arsenic is not lethal for those organisms, but "not lethal" and "sustaining life" are just not the same.
(3) Incorporation of arsenate in DNA will result in a defect, because arsenate esters, unlike phosphate esters, are very susceptible to hydrolysis. However, this usually does not have a noticeable effect, (1) because the genetic information is duplicated in the DNA molecule and the second strand will still hold all the information when the first strand is broken, (2) because a break in the backbone will not necessarily result in a break of the strand, since there are enzymes active which do repair such defects. Unlike the chemical modification of a base that holds genetic information (phosphate or arsenate do not), which will inevitably result in a mutation, defects in the backbone are "simple" defects, which occur frequently in all organisms.
(4) The question whether arsenate may also be incorporated in ATP is easily answered, because this topic has been extensively researched in the past (a short explanation is given in Stryer, L.: Biochemistry, Freeman & Company (New York), > 1000 pp.). It does not, but in the presence of arsenate, ATP does not form either. Arsenate breaks the reaction chain by uncoupling the phosphorylation and oxidation steps. Glycolysis still proceeds, but the ATP normally formed in the conversion of the phosphate ester intermediate is lost, because the As analogue is highly labile and will hydrolyze before the enzyme-catalyzed phosphate transfer takes place.
David Von Bargen December 07, 2010 02:26PMThis looks like an extreme long shot to make any difference to exobiology. If you look at the cosmic abundances of phosphorus and arsenic, you are looking at ratios of 100:1 to 1000:1. There really aren't all that many environments where you would have enough arsenic with a lack of phosphorus for these types of reactions to work.
Alfredo Petrov December 07, 2010 02:32PMYes, and without plate tectonics arsenic (and other heavy elements) is unlikely to accumulate anywhere. I'm not sure how common plate tectonics will be on exoplanets. There doesn't seem to be much of it on any other rocky planet in the Solar System. I'd have expected plate tectonics to operate on Venus, considering it's almost a sister planet to Earth, but there doesn't seem to be.
Rob Woodside December 07, 2010 04:23PMAlfredo, all you need is internal heat to drive mantle convection and a lubricant like water for tectonics to work. So while we could pile huge ice balls from the Ort cloud into Mars or Venus to terraform them, only Venus has the internal heat now for tectonics to start.
In the last few years there's been a couple of Nova programs about the earth's magnetic field. According to these programs the earth's magnetic field protects us from the scorching solar wind that would otherwise blow away our atmosphere. The proof they say is Mars with no large dipole field and little atmosphere. They fail to mention Venus with an oppressive toxic atmosphere and no large dipole field. Once mantle convection developed on Venus it would be amusing to see if a large dipole magnetic field would also appear.
I think the sad thing here is that Science of itself is absolutely fascinating and we don't need alien or doomsday spins to make it so.
Georg Graf December 07, 2010 08:16PMHi All,
my sugestion: Life based on B-N-B-N- chains on planets like Jupiter. E. g. Borazole B3N3H6 is very similar to Benzene C6H6. Of course there are differences, e. g. the B-N bonding is a little bit polarized, the c-c bonding is not.
One day man send a probe to research Jupiters atmosphere. Some month later radio signals from Jupiter are disturbing all radio signals on earth. The signals from Jupiter have structure and content: Numbers; prime numbers; a periodic table of elements (ending with lead); ...
Dreaming in Thale near Goslar of a fantastic future
gord major December 09, 2010 03:11PMI remeber reading a book about Western sheepherders who carried and based on memory arsenic to bait the dead sheep.
Since they carried it in their pocket and were not scrupulous in the handling such arsenic build up a tolerance to arsenic.
How does this relate to the MONO arsenic uptake?
Noah Horwitz December 09, 2010 04:36PMI've read that Venus is thought to once have had an ocean and plate tectonics. But eventually the planet heated up and the ocean boiled away. This removed the lubricant for plate tectonics, and without tectonics to disperse energy (presumably from radioactive decay in the planet's core), the crust gets "resurfaced" by massive lava flows every once in a while. It's an interesting theory, but apparently no one's been able to collect rock samples from Venus and date them to confirm it.
Rob Woodside December 09, 2010 04:45PMIf Nasa spent some of their Manned Space program money on robotics we'd have those samples by now :X
The initial visitors to venus never made it to the surface, But with that info the Russians made it to the surface and got photos through a diamond window before the lander died within minutes of arrival.
Chris Stefano December 09, 2010 07:01PMThe temperature of the Venutian surface is actually hot enough that the crust is significantly more ductile than ours. There is no reason to believe that Venus does not have mantle convection, but tectonics with a ductile crust should be expected to look a lot different from what we see on Earth.
Steve Hardinger December 13, 2010 03:38PMThe "arsenic in DNA" publication was rubbish when published, and is now under significant scrutiny. See for example: http://www.cendigital.org/cendigital/20101213?sub_id=GHKCQoWslGl4#pg9
Alfredo Petrov July 09, 2012 06:38PMAnd a year and a half later, to update this topic, it seems to get increasingly debunked:
Bart Cannon July 10, 2012 09:10AMNASA's Felisa Wolfe-Simon's theory about arsenic based life forms is COMPLETELY dead in the "water".
This in no way suggests that microbes which metabolize arsenic do not exist.
If there is a chemical bond, a microbe will evolve to exploit the energy potential.
NASA is a shameless promotional organization. They are desperate for news potential.
Could any Mindater do a bioassy on a weathering arsenopyrite sample ?
Edited 2 time(s). Last edit at 07/10/2012 01:58PM by Bart Cannon.
Frank Keutsch July 10, 2012 11:22AMBart,
"microprobes which metabolize arsenic"... is your microprobe a living being? I do sometimes have that impression, as they sometimes seem to develop a life of their own.
I have been pondering your question though as it is of considerable commercial interest, e.g., gold mining.
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