Adaption to extreme nuclear acidity -- possible?

[Green Xenon]

Hi:

 

The acetic acid bacterium has an acidic cytoplasm but the nucleus is still pH-neutral. Is it possible for the proteins, DNA/RNA, and other organic molecules of a living cell to somehow adapt to pH of 0? If not, then what is the lowest pH the cell [including the nuclear molecules] can adapt to?

 

 

Thanks,

 

GX

[mississippichem]

Hi:

 

The acetic acid bacterium has an acidic cytoplasm but the nucleus is still pH-neutral. Is it possible for the proteins, DNA/RNA, and other organic molecules of a living cell to somehow adapt to pH of 0? If not, then what is the lowest pH the cell [including the nuclear molecules] can adapt to?

 

 

Thanks,

 

GX

 

Well, I don't know what the actual limit is. However, at some low pH, stuff will begin to hydrolyze. Also, a very low pH might mess with the hydrogen bonding scheme of the nucleobases once everything gets protonated. You might end up with non-Watson-Crick base pairing (stuff like T-T or A-C) or no base paring at all. It's actually an interesting question. I'm sure the biochemers around here know a lot more.

[Tr0x]

The molecular components of cells are actually quite fragile, and require a protective coating of sorts to survive in extreme environments such as extreme pH (i.e. cell membranes/walls). Acidophiles usually have powerful ion pumps within the membranes, which effectively maintain a neutral pH in the cell.

 

None of that really answers your question though...just showing that life can generally get around having to completely change its biochemistry in order to deal with acidic environments.

 

A pH of 0 in the cell and nucleus would be tricky to withstand, as protein folds are very sensitive to pH. Assuming the pH remains constant, and given enough time, pH sensitive proteins could conceivably evolve to better fold at low pH (though they may not maintain the same efficiency or even function) . But at this low of a pH, hydrolysis would be running rampant, and probably chewing up peptides, and sugars (i.e. phosphate-deoxiribose backbones of DNA).

 

If the organism could somehow shield it's DNA chemically (i.e. glycosylating it constantly) then MAYBE it could withstand having a pH 0 in the nucleus. But this would require a rediculous amount of energy for the cell...and converting the low pH into a form of energy wouldn't work in this case, as that would require a gradient/a higher pH in the cell than the outside.

 

As for the lowest pH an organism can adapt to...well apparently you can ignore most of my above conjecture as there is an archaea that can survive pH 0...and apparently without a cell wall! Review articles citing the one I linked to would be worth a read. Whether or not the pH is acidic/neutral in the nucleus wasn't discussed.

 

Oh, and while looking up answers for this, pH can apparently even be negative! Now THAT would be tricky to survive!

[CharonY]

Bacteria do not have a nucleus. The lowest measured intracellular pH that I came across in bacteria (and remembered) was around 5.

 

Edit: short sentences and I managed to introduce numerous typos. I suck.

Edited August 5, 2011 by CharonY

[Tr0x]

Bacteria do not have nucleus.

 

Oh wow how could I forget that?! I need to brush up on my basic biology apparently

 

The article I cited stated that the organism didn't have any significant membrane/cell wall beyond the ordinary. This suggests that the cytoplasm is likely acidic as well...but to what degree it didn't say.

Edited August 4, 2011 by Tr0x