bacteria that eat rock and need no oxygen

[Fishteacher73]

Originally Posted by alxian

i'm wondering if their could be a super creature capable of tackling all known toxins and if their are any trully toxic compounds no life form can actually deal with.

While it is amazing at the diversity of bacteria and where they can thrive (On a return Apollo mission they found a strain of staph. that had continued to live in camera left ion the moon for two years). So we are continually having to edge back what we think the boundries of life are, and it the bacteria that are leading the way.

As for toxic compounds...IMO there probably are some man-made compounds that are pretty much universally toxic to all life (maybe given time some will be immune or even thrive with it). So I did some digging...The Merk Index lists a family of seven different proteins produced by the Clostridium botulinum bacterium, these are the ones that cause botulism. These seven toxins have a median lethal dose in mice of 0.0000003 mg of botulin/kg of body mass in mice.
This is the smallest LD50 listed. (For comparison Ricin has a LD50 of 0.001 mg of ricin/kg of body mass)
But surprisingly thse compounds are organic in nature and NOT mand-made....So much for that initial idea....
The most toxic man-made are the dioxin family, but they have a LD50 of 0.045 mg of dioxin/kg of body mass for rats. (over 100,000 times that of the botulism toxin).

[alxian]

so then maybe a uranium munching bacteria isn't so far fetched after all hmm? excellent

[Fishteacher73]

Originally Posted by alxian

so then maybe a uranium munching bacteria isn't so far fetched after all hmm? excellent

Not far fetched, but likely....

[TeleMad]

Originally Posted by Fishteacher73

... (On a return Apollo mission they found a strain of staph. that had continued to live in camera left ion the moon for two years).

Actually, it was a streptococcus.

“At the other extreme, viable specimens of the bacterium Streptococcus mitis were retrieved from the surface of the Moon, where they endured a complete vacuum for two years while attached to a camera housing on the Surveyor III spacecraft.” (The Fifth Miracle: The Search for the Origin and Meaning of Life, Paul Davies, Simon & Shuster, 1999, p 165)

“Streptococcus mitis survived 31 months in the space environment in a contaminated Surveyor spacecraft on the surface of the moon(10)” (Evolution on planet Earth: origins and achievements, David D. Wynn-Williams, Trends in Ecology & Evolution, 1999, 14:10:379-381: the (10) reference, listed at the end of the article, is: (10) Apollo Program Summary Report (1975) Section 3.2.28 Surveyor III Analysis, in vol. JCS-09423, NASA, Houston”.

[TeleMad]

alxian: i'm wondering if their could be a super creature capable of tackling all known toxins and if their are any trully toxic compounds no life form can actually deal with.

Someone suggested radiation, but first, it's not a compound, and second, as Fishteacher73 pointed out, some bacteria thrive in radiation.

You do raise an interesting question. For example, cyanide (CN-) is a poison because it binds to the final cytochrome of the electron transport chain, stopping the flow of electrons and thus the production of ATP. Yet cyanide is considered to have been prevalent during the origin of life (and many organic compounds are thought to have been formed by the repeated combining of hydrogen cynaide (HCN) molecules).

Since life can probably survive without proteins, but not without nucleic acids, and could possibly be as simple as a self-replicating RNA, the universal toxin would need to destroy nucleic acids somehow. Maybe it's just some concentrated strong acid, like H2SO4, HNO3, HCLO4, HCL, HBr, or HI.

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PS: Forgot for a moment that there are bacteria that live in highly acidic solutions. So that kills my latter idea of H2SO4 or some other strong acid being a universal poison.

Apparently, the strong acid does not make it all the way to the DNA because I believe if it did it would destroy the DNA. I'm guessing that the flow of protons into the bacterium is used to make ATP by chemiosmosis (which I know occurs in many bacteria) at the periphery of the cell, with the protons then being pumped back out of the cell in the process: if the inside became more acidic than the outside, chemiosmosis would stop - so the bacteria would need to maintain the inside at a higher pH than the outside and the continuous pumping of protons out of the cell would prevent the strong acid from destroying the DNA.