http://www.huffingtonpost.com/2010/12/02/nasa-could-announce-arsenic-eating-bacteria_n_790954.html WASHINGTON — The discovery of a strange bacteria that can use arsenic as one of its nutrients widens the scope for finding new forms of life on Earth and possibly beyond. While researchers discovered the unusual bacteria here on Earth, they say it shows that life has possibilities beyond the major elements that have been considered essential. "This organism has dual capability. It can grow with either phosphorous or arsenic. That makes it very peculiar, though it falls short of being some form of truly 'alien' life," commented Paul C. W. Davies of Arizona State University, a co-author of the report appearing in Thursday's online edition of the journal Science. Six major elements have long been considered essential for life – carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. But the researchers found that the bacteria, discovered in Mono Lake, Calif. , is able to continue to grow after substituting arsenic for phosphorous. "It makes you wonder what else is possible," said Ariel D. Anbar of Arizona State University, a co-author of the report. The find is important in the search for life beyond Earth because researchers need to be able to recognize life, to know what life looks like, Anbar said. The study focuses on a microbe found on Earth. However, the announcement of a news conference to discuss it, which did not disclose details of the find, generated widespread speculation on the Internet that the report would disclose the discovery of extraterrestrial life. It didn't. The discovery "does show that in other planetary environments organisms might be able to use other elements to drive biochemistry and that the ' standard' set of elements we think are absolutely necessary for life might not be so fixed," commented Charles Cockell, professor at the Planetary and Space Sciences Research Institute, Open University, in Milton Keynes, United Kingdom. Cockell was not part of the research team. Story continues below Advertisement "This work is novel because it shows the substitution of one element for another in fundamental biochemistry and biochemical structure," added Cockell. It wasn't a chance discovery. Felisa Wolfe-Simon of NASA's Astrobiology Institute, who led the study, targeted Mono Lake because it has high arsenic levels. Arsenic and phosphorous are chemically similar, so she speculated that a microbe exposed to both might be able to substitute one for the other. "Arsenic is toxic mainly because its chemical behavior is so similar to that of phosphorus. As a result, organisms have a hard time telling these elements apart. But arsenic is different enough that it doesn't work as well as phosphorus, so it gets in there and sort of gums up the works of our biochemical machinery," explained Anbar. The researchers collected the bacteria known as GFAJ-1 and exposed it to increasing concentrations of arsenic, which it was able to adapt to and grow. The microbe does grow better on phosphorous, but showing that it can live with arsenic instead raises the possibility that a life form using arsenic could occur naturally, either elsewhere on Earth or on another planet or moon where arsenic is more common. Jamie S. Foster, an assistant professor of microbiology at the University of Florida, said the idea that arsenic could be substituted for phosphorous isn't new, but there has never been example where it was shown to work. Arsenic was more common in the early times on Earth, she said, so researchers have speculated that early life forms might have used it. "It does suggest that that there could be other ways to form life, not just how life formed on early Earth," said Foster, who was not part of Wolfe- Simon's research team. The research was supported by NASA, the Department of Energy and the National Institutes of Health.
【在 T**********t 的大作中提到】 : http://www.huffingtonpost.com/2010/12/02/nasa-could-announce-arsenic-eating-bacteria_n_790954.html : WASHINGTON — The discovery of a strange bacteria that can use arsenic as : one of its nutrients widens the scope for finding new forms of life on Earth : and possibly beyond. : While researchers discovered the unusual bacteria here on Earth, they say it : shows that life has possibilities beyond the major elements that have been : considered essential. : "This organism has dual capability. It can grow with either phosphorous or : arsenic. That makes it very peculiar, though it falls short of being some : form of truly 'alien' life," commented Paul C. W. Davies of Arizona State
what r u still arguing? no matter whatever way it goes through, if they have shown the As completely replace the Pi in the DNA/RNA, that's huge/ milestone in the textbook unless someone else has demonstrated that before.. .talking about imagination or in fiction, I think many of us have been wondering why life has to be made of those elements...why not even Fe or whatever...Why there has to be water or whatever...the alien could be made of metals and live on Metals as well, who knows...I am crazy now...
【在 n********k 的大作中提到】 : what r u still arguing? no matter whatever way it goes through, if they have : shown the As completely replace the Pi in the DNA/RNA, that's huge/ : milestone in the textbook unless someone else has demonstrated that before.. : .talking about imagination or in fiction, I think many of us have been : wondering why life has to be made of those elements...why not even Fe or : whatever...Why there has to be water or whatever...the alien could be made : of metals and live on Metals as well, who knows...I am crazy now...
s*y
44 楼
另外啊,某些过渡性金属,还真的说不定可以作为life form basis, 因为它们可以形成稳定多键复合物。
have ..
【在 n********k 的大作中提到】 : what r u still arguing? no matter whatever way it goes through, if they have : shown the As completely replace the Pi in the DNA/RNA, that's huge/ : milestone in the textbook unless someone else has demonstrated that before.. : .talking about imagination or in fiction, I think many of us have been : wondering why life has to be made of those elements...why not even Fe or : whatever...Why there has to be water or whatever...the alien could be made : of metals and live on Metals as well, who knows...I am crazy now...
【在 s****t 的大作中提到】 : interesting finding if it's indeed the case. : Can anyone send me a copy of science paper, please? : s******[email protected] : thanks.
In fact, it opens up tons of questions/opportunity---in term of DNA. RNA and Protein functions and regulation as well...so a next key question would be whether it is just an evolution accident or it has wider implication, e.g: it ever happens in other organism such as human, do As ever get into our DNA /RNA/protein and play any functional/regulatory roles? BTW, u are too greedy...if it doesn't need this DNA stuff, it would be an instant nobel....However, I always think everything is possible, life could well exist in isoforms other than us, it could be like a coahesive liquid, or like you said, use reduction, so O2 is toxic...
G. Miller, and J. F. Stolz. 2005. A microbial arsenic cycle in a salt- saturated, extreme environment: Searles Lake, California. Science. 308:1305- 1308.
L. G. Miller, and J. F. Stolz. 2005. A microbial arsenic cycle in a salt- saturated, extreme environment: Searles Lake, California. Science. 308:1305-1308. arsenic-metabolism-new-twists-on-an-old-poison
Some paper said that the cost of As resistance is low. And As resistance has been identified in many different species. For this strain (NASA have found), the growth rate is really slow(this is normal for such strains). After 480h, the total cells just increased about 10 folds(from 10e6/ml to 10e7/ml). So the demanding of phosphorus may be small. And after 120h, this strain reaches stationary phase. I don't know if they are still alive after 480h.
s*7
133 楼
L. G. Miller, and J. F. Stolz. 2005. A microbial arsenic cycle in a salt- saturated, extreme environment: Searles Lake, California. Science. 308:1305-1308. arsenic-metabolism-new-twists-on-an-old-poison it is a different story. this paper is about a bacteria using As as energy source. nasa's paper is using As in DNA.
G. Miller, and J. F. Stolz. 2005. A microbial arsenic cycle in a salt- saturated, extreme environment: Searles Lake, California. Science. 308:1305- 1308.
G. Miller, and J. F. Stolz. 2005. A microbial arsenic cycle in a salt- saturated, extreme environment: Searles Lake, California. Science. 308:1305- 1308.
Accumulation of PHB is very common in the bacteria under imbalanced growth conditions, especially nitrogen/Pi limitation. This is one of storage compounds. Furthermore, some algae can produce higher content of lipids under such conditions. Maybe PHB has other functions.
I saw the news yesterday and have a chance to read the paper in detail today. It was very exciting if proved, but right now I'm still not 100% convinced for the following reasons: 1. The authors showed that cells grow better in media containing +As/-P, than -As/-P. Could that be explained that As (40 mM Arsenate) stimulate the cells to uptake PO4? The author never really got rid of trace amount of PO4 in his experiment to give a clear conclusion. Also, the authors only showed one concentration of arsenate (40 mM), it will be more convincing if they show a better growth of the cells with a gradient concentrations of Arsenate in the media (Fig. 1A). 2. One of the most important data to show the amount of As in cells in the +As/-P media is worthless: 0.19+/-0.25 is meaningless. The author's explanation was that because the cells were harvested at stationary phase, then why didn't they take cells at late log phase since this data is so important for his conclusion? 3. The authors showed As was incorporated into biomolecules including DNA, proteins and metabolites by showing isolated biomolecures contain As. But how to determine whether As was incorporated during the cell growth or were simply labeled during the extraction process since there is plenty of As in the media? 4. I'm curious whether this strain contains a Arsenate detoxification gene, and the role of this gene in the cells. Can the cells still grow better with Arsenate in media if this gene is knocked out? This might be related to question 1.
c*1
148 楼
I saw the news yesterday and have a chance to read the paper in detail today. It was very exciting if proved, but right now I'm still not 100% convinced for the following reasons: 1. The authors showed that cells grow better in media containing +As/-P, than -As/-P. Could that be explained that As (40 mM Arsenate) stimulate the cells to uptake PO4? The author never really got rid of trace amount of PO4 in his experiment to give a clear conclusion. Also, the authors only showed one concentration of arsenate (40 mM), it will be more convincing if they show a better growth of the cells with a gradient concentrations of Arsenate in the media (Fig. 1A). 2. One of the most important data to show the amount of As in cells in the +As/-P media is worthless: 0.19+/-0.25 is meaningless. The author's explanation was that because the cells were harvested at stationary phase, then why didn't they take cells at late log phase since this data is so important for his conclusion? 3. The authors showed As was incorporated into biomolecules including DNA, proteins and metabolites by showing isolated biomolecures contain As. But how to determine whether As was incorporated during the cell growth or were simply labeled during the extraction process since there is plenty of As in the media? 4. I'm curious whether this strain contains a Arsenate detoxification gene, and the role of this gene in the cells. Can the cells still grow better with Arsenate in media if this gene is knocked out? This might be related to question 1.
S*I
149 楼
如果能提取纯化细菌的DNA做个晶体结构就清楚了。
【在 c********1 的大作中提到】 : I saw the news yesterday and have a chance to read the paper in detail : today. It was very exciting if proved, but right now I'm still not 100% : convinced for the following reasons: : 1. The authors showed that cells grow better in media containing +As/-P, : than -As/-P. Could that be explained that As (40 mM Arsenate) stimulate : the cells to uptake PO4? The author never really got rid of trace amount : of PO4 in his experiment to give a clear conclusion. Also, the authors : only showed one concentration of arsenate (40 mM), it will be more : convincing if they show a better growth of the cells with a gradient : concentrations of Arsenate in the media (Fig. 1A).
M*a
150 楼
They are totally different stories. Some dissimilatory metal-reducers can use As(V) as an electron acceptor and reduce As(V) to As(III). Lots of papers are available. Some bacteria such as Shewanella and Geobacter spp. can even reduce U(VI) to U(IV). These are dissimilatory reduction. The recent NASA discovery talks about incorporating an alternative element of one of the so called "essential elements" for life in bacterial biomass. In their experiments, oxygen was the electron acceptor.
When I was graduate, I did plant cell culture without phosphate. Clearly, cells grew by several-fold without phosphate or arsenic. Can I claim that a special plant cell culture can grow without phosphate, only five elements needed. The real trick is that the plant cells store a lot of phosphate in the initially-tested cells. The NASA paper may have the same situation. Some one has commented this possibility in the same issue of Science. Clearly, Science editors are zo shameless to ignore this possibility and do not ask the authors to test this possibility. In fact, this possibility can be eliminated easily. Transferring the stationary of cells growing on arsenic-only medium to another fresh arsenic-only media for growth testing. My guess is no growth at all. Do not take Science papers seriously any more. Recently they published so many non-sense or weak papers.