Deinococcus Radiodurans Durability
Just wondering if anyone could explain to me how its possible that organisms like Deinococcus radiodurans which we discussed in yesterdays lecture are able to withstand temperature extremities (think it was -150C or +150C?).
What is about their organic structure that gives them this durability?

Patrick Slater (u5018801)




I don't know details, so someone else please chime in, but the basics are:





One relevant fact that I forgot to mention in the lecture is that many bacteria spend most of their time dormant anyway. In fact, it's possible that most of Earth life consists of dormant bacteria. In the dormant state, the bacteria are not metabolising (or, of course, growing or reproducing) — they're just waiting for a better environment to come along, and if/when it does they start metabolising again. So bacteria have had lots and lots of practice at being dormant and then reviving when a suitable environment comes along.

I hope someone will add more details, but anyway I hope you get the picture, that the abilities of Deinococcus radiodurans are actually quite widespread among Earth organisms, although to a lesser degree in most other organisms. We really don't know much about this yet, but it's possible that a lot of organisms can survive in space.

Jason




Hi.

As mentioned, it is easy for bacteria and some insects to remain alive under subfreezing conditions. One of the reasons behind this is they have anti-freezing agents such as glycerol. It has been shown that in larvae of goldenrod gall moth, their glycerol content is in fact, seasonal. When temperature drops (particularly during early autumn), their physiological concentration of glycerol increases. Besides, there are also some anti-freeze proteins which can disrupt the formation of ice particles within these organisms.

As for the heat endurance of some extremophiles, I believe it also has something to do with the folding of proteins within them, other than relying solely on protective chemicals. Prion proteins can remain viable even when heated to a high temperature. This is why meats from infected sources are not consumable even though they are cooked at high temperature (scrapie is a good example here). More detailed information regarding the folding of this class of proteins are needed to explain the issue completely and I'm all ears for it. Moreover, there is a class of protein named 'small heat-shock protein'. It is named so because once these proteins are subjected to heat and be destabilised, some molecular chaperones are able to convert them back to their native functional states.

Goh Tze How
(u5167200)




Thanks, How!

Jason




That's fascinating How. The tertiary protein bonds must certainly be broken and the protein denatured at 150 degrees but I wonder why the protein structure of the "chaperones" is not denatured rendering them useless (as they surely must be protein structures themselves?)?
Fascinating too that glycerol/anti-freeze can reach high concentrations as I believe it inhibits the ATP production of energy (so a poison to humans).
In biology, there's always another way of doing things!

Senan.




"In biology, there's always another way of doing things!"

That's exactly what I'm hoping is the take-home message of this part of the course.

Boring for you if you already knew that. :-)

Jason




Aha! I've just found out that one of the ways organisms can survive very cold conditions is by dehydrating. See https://en.wikipedia.org/wiki/Tardigrade

Jason