So the big headline on all the scientifically illiterate news channels today (until they lost interest) was NASA's press release on a new biological discovery. It was painful watching news anchors try to process something meaningful out of the scientific explanation - most of them were expecting little green men and cut out of the press release after the first 5 minutes.

Basically, what I had been taught throughout school was that DNA was made of C, H, 0, N, P and that this is how every single living thing on the planet was defined.

Now they find a microorganism that lives in an area of highly concentrated Arsenic that substituted the Phosphorus element in its DNA, with Arsenic! Rewrite the biology books! Having a biochemistry major, this came as a mind-blowing discovery.

The interesting question: is this an adaptation, or a product of an entirely different genesis than our own? One thing for sure, we have never seen any living thing with this property, so as far as I'm concerned - it's an alien

The wiki on Phosphorus says that: "Because phosphorus is just below nitrogen in the periodic table, the two elements share many of their bonding characteristics"

Also the wiki on Arsenic states that: "Arsenic compounds resemble in some respects those of phosphorus"

So, *maybe*, it isn't really that chemically crazy that one can take the place of another... But I've never been a chemistry lover so I could be completely wrong.

Either case I'll bump your thread with a beautiful picture of the Periodic Table for everyone to enjoy!

we don't yet know anything about these organisms other than their use of arsenic as an element in their DNA; I'm sure in the next few years, they will be well documented.

I suspect it evolved from some kind of Prokaryote. These cells lack any internal structures, having their DNA in a nodule in their centre, and many species obtain energy from the reactions of chemicals such as arsenic. Many are extremophiles, because their simpler internal structure allows them to survive otherwise damaging environments.

My psudoscientific theory is that they came about when arsenic, which can form many of the same chemical bonds as phosphorus but is a lot less stable, simply began to bond with the DNA of cells which routinely drew energy from arsenic and thus had a tolerance to its normally toxic properties. For this to happen, the cell would have to somehow live in an environment where there was an abundance of free radicals of arsenic.

tldr; this probably evolved from an archaea or bacteria which had a habit of keeping free radicals of arsenic inside its membrane, rather than being a seperate instance of life forming.

Quote: Original post by owl
So, *maybe*, it isn't really that chemically crazy that one can take the place of another... But I've never been a chemistry lover so I could be completely wrong.

It's not that chemically crazy, the reason arsenic is so deadly to us is because its so close to phosphorus and it stuffs up our chemical pathways.

In the grand scheme of things its not that surprising to find life has managed to make use of arsenic; a little more so that such life exists here but not so out there as to be unbelievable.
(I also watched something a few years back which speculated there would be life 'out there' which is based on arsenic.)

What it goes to show is that life finds a way, reminds me of something else I heard on a TV program once; the universe tends towards life, so much so it seems almost inevitable.

"Life abhors a vacuum."

It certainly isn't chemically surprising and was in fact hypothesized for a while because these kind of substitutions have been known to happen in other biological processes - but what is important about it is that it demonstrates adaptability at the lowest level of DNA and its primary biomolecules (proteins etc). It shows that what we believed to be the essential chemical makeup of all living things can be fudged.

On a surface level it seems logical, but the scientific implications go beyond that.

I havent read the actual announcement, but from what i've read on another forum, this may not quite be as big a discovery as first thought.

My (limited) understanding is that because Arsenic is very similar to Phosphorus, it tends to form similar bonds to phosphorus. Therefore if arsenic is injested into the boddy, it will bond with ATP and Proteins, but because it is less stable, it tends to break down, causing problems transporting energy around the body. This usually proves fatal.

I believe what they have discovered is a microbe that is able to function in an arsenic rich environment, and shows signs that its structure consists of arsenic. However I believe traces of phosphorus have also been found in this microbe, so at present it is not known whether this microbe can simply tolerate the presence of phosphorus and continue to function, or if it uses arsenic instead of phosphorus ...

Quote: Original post by speciesUnknown
we don't yet know anything about these organisms other than their use of arsenic as an element in their DNA; I'm sure in the next few years, they will be well documented.

I suspect it evolved from some kind of Prokaryote. These cells lack any internal structures, having their DNA in a nodule in their centre, and many species obtain energy from the reactions of chemicals such as arsenic. Many are extremophiles, because their simpler internal structure allows them to survive otherwise damaging environments.

My psudoscientific theory is that they came about when arsenic, which can form many of the same chemical bonds as phosphorus but is a lot less stable, simply began to bond with the DNA of cells which routinely drew energy from arsenic and thus had a tolerance to its normally toxic properties. For this to happen, the cell would have to somehow live in an environment where there was an abundance of free radicals of arsenic.

tldr; this probably evolved from an archaea or bacteria which had a habit of keeping free radicals of arsenic inside its membrane, rather than being a seperate instance of life forming.

Yes what ever happened to the extremophiles and other interesting forms of life that we have known about for years?
I don't see what the connection to extraterrestial life is coming into play in all this?
Even the wikipedia entry for extemophiles is showing this GFAJ-1 as falling under it.
http://en.wikipedia.org/wiki/Extremophile

Sounds to me that maybe some of these other extemophiles are just as mysterious since they live in hostile/extreme enviornments which would make testing them difficult at best.

p.s. I also recall someone(can't remember exactly at the moment might've even been Carl Sagan?) postulating a while back about the possibility of silicon based life and how we are biased by looking for carbon based life.

Quote: Original post by daviangel
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I don't see what the connection to extraterrestial life is coming into play in all this?...

Basically, proof that a DNA like molecule can exist in an actual lifeform, is proof that yet another form of life can exist on other planets. There are lots of Hypothetical forms of biochemistry which are not based on hydrocarbons, phosphorus etc. The formation of life depends on a string of coincidences, and this discovery increases the numbers of possible scenarios for life to evolve. Basically, the number of possible places for life to evolve just increased tenfold.

The LA Times article said that it was a relative of E. Coli, or at least genetically similar to it (near the end of the first-page text.