Do brine pools preserve genetic material?

Submitted by Vonnie610 t3_11q9x51 in askscience

So I know that the reason we don’t have dino DNA from fossils is that they are… fossilised. So all the info has been replaced by rocks (or at least that is my very basic understanding).

I watched a video about these brine pools (AKA underwater lakes) where sea critters fall in and die. In the video they looked really well preserved and I wanted to know if the DNA is still available in those pickled critters or if the same fossilisation process happens but with salt.

Bonus question is if that DNA info is valuable/helps us understand more!

https://i.imgur.com/6jGDnqI.jpg

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S_A_N_D_ t1_jc4fek2 wrote

This is a relevant article on the subject.

https://www.nature.com/articles/nature.2012.11555

>After cell death, enzymes start to break down the bonds between the nucleotides that form the backbone of DNA, and micro-organisms speed the decay. In the long run, however, reactions with water are thought to be responsible for most bond degradation. Groundwater is almost ubiquitous, so DNA in buried bone samples should, in theory, degrade at a set rate.

Basically, unless the sample is preserved under unnaturally dry conditions while also conveniently protected from all other sources of degradation (something that is unlikely to happen naturally), you're looking at best case scenario of ~7 million years, though the most likely would be ~1 million years.

As water is the main contributing factor, it's unlikely salt water would have any significant net positive effect on preservation length of time.

Edit: Here is an article I found that suggests high salt anoxic conditions will have a net protective effect, however the study does have some limitations. Overall, it might suggest that a high salt environment might help skew the half life to the longer end of the spectrum, though I'm unable to suggest it may extend it beyond that to any significant degree.

https://www.nature.com/articles/srep22960

Also I didn't truly answer your question. I would expect that we would be able to extract DNA from the organisms you are looking at in those salt pools, however the success would decrease with time. After about 500 years, about 1/2 the DNA bonds would be broken, and 500 years after that another half would be broken. We can piece together fragments of DNA to make up the whole (sort of like piecing a puzzle back together), but the chance of success would decrease with time. The further back you go, the more samples you'd need to get a complete picture, and after about a million years the task would pretty much become impossible even if you had an abundance of well preserved samples.

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figmentPez t1_jc5hnvi wrote

Replying to S_A_N_D_ (#2,223,848)

>it's unlikely salt water would have any significant net positive effect on preservation length of time.

Given that high salt concentrations denature proteins, I'd suspect that the opposite is the case. Salt so concentrated that it causes life to die seems like it would cause DNA to break down faster.

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S_A_N_D_ t1_jc5j4r1 wrote

Replying to figmentPez (#2,225,793)

Protein denaturation happens because the tertiary structure is broken as the charged and polar interactions of each residue are broken or disrupted. Salt will have little impact on the peptide bond.

Death due to salinity is usually due to organisms being unable to maintain a proper intracellular osmotic balance rather than from direct protein denaturation.

Hypersaline solutions may cause some of the DNA to precipitate, however I'm not sure if it will have a net negative, or net positive effect. I'm actually leaning towards it possibly having a protective effect, but I'm not sure I have the background in biochemistry necessary to say that from a position of authority.

Overall though I expect it would be unlikely to make any measurable change to the numbers listed above, especially since the calculated half life was for samples that were buried and are therefore surrounded by a lot of minerals as well, and therefore also likely salts. I'm guessing any protective effect from our example would be insignificant.

Edit: Here is an article that does suggest high salt concentrations have a net protective effect on DNA preservation in the environment, though the study does suffer from some major limitations so we are unable to conclude to what degree this would have relative to the paper I mentioned in my first post. I expect it might skew the half life to the longer end of the range, but to what degree I can't speculate.

https://www.nature.com/articles/srep22960

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