NASA Finds New Life (Bacteria uses Arsenic instead of Phosphorous)

[Ian David]

NASA Finds New Life
http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=102&topic_id=4638937&mesg_id=4638937

[struggle4progress]

1. Bacteria first species observed to use arsenic-laced DNA backbone

... Evolutionary geochemist Felisa Wolfe-Simon, the lead author, and her colleagues found a strain of bacterium (GFAJ-1 of the Halomonadaceae family) that can grow in a medium abundant in arsenic and lacking phosphorus. The GFAJ-1 bacterium naturally resides in the arsenic-rich waters (200 uM) of Mono Lake located in California's Eastern Sierra, and it belongs to a family of proteobacteria that is known to accumulate arsenic. It's not remarkable that GFAJ-1 survives in high concentrations of arsenic, but what is startling is that it potentially integrates arsenic into its DNA and proteins.

Arsenic is chemically similar to phosphorus, which has a large presence in biomolecules in the form of phosphate (PO43-). That’s partly why arsenic is so toxic. In physiological conditions, phosphate and arsenate (AsO43-) are analogous enough that some metabolic pathways cannot tell them apart initially. But incorporation of arsenic disrupts later steps in these pathways, most likely due to arsenic compounds’ relative instability and lower resistance to hydrolysis.

The researchers propose that, if an organism possesses an ability to overcome arsenate’s instability, it might be able to exchange phosphorus for arsenic in biological pathways. To test their hypothesis, they extracted GFAJ-1 from Mono Lake and subjected the bacteria to an artificial medium with increasing concentrations of arsenate and only trace amounts of phosphate.

GFAJ-1 bacteria grew slower with arsenate than they would with phosphate, but they were still able to increase their cell count by 20-fold in six days. The cells ended up containing 0.19 percent arsenic by dry weight compared to just 0.001 percent in the control cells. More importantly, the cells grown in arsenate were noticeably different in morphology from the control population. They were 1.5 times bigger by volume and developed large vacuole-like regions inside the cells ...

http://arstechnica.com/science/news/2010/12/bacteria-can-integrate-arsenic-into-its-dna-and-proteins.ars

[struggle4progress]

2. Researchers Discover Microbes That Live on Arsenic

... Force-grown in the laboratory, these bacteria use the notorious poison to replace molecules of the element phosphorus in critical parts of their working biology, including in the spiral backbone of DNA, which is a crucial component for all known life, the researchers said. By depending on an element so toxic to normal life, the microbes are a living demonstration of the exotic substances that alien biochemistry might, in theory at least, use on other worlds.

"It is building itself out of arsenic," said geo-microbiologist Felisa Wolfe-Simon at NASA's Astrobiology Institute and the U.S. Geological Survey, who led researchers from eight federal and university laboratories conducting the experiment. "All life we know is the same biochemically, and this is a little different. It is suggesting there is another way to be alive."

The researchers conceded, however, that by themselves these odd microbes don't prove yet that there is a fundamentally different basis for life on Earth. "It is beginning to open the door a crack to possibilities," she said.

Several independent experts were convinced that these unusual organisms were not so far out of the ordinary. "This is an interesting curiosity, a novel discovery but not a paradigm-breaking one," said New York University chemist Robert Shapiro, an authority on DNA and the origin of life who was not involved in the project. "It is a cousin of known living things that has some peculiar habits" ...

http://online.wsj.com/article/SB10001424052748703377504575650840897300342.html

[denbot]

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