In some of my experiments I have been working on heat shock experiments of a temperature range of 40-50oC for 2-30 minute time periods.
What I have found is that there seems to be a temperature switch at 44-48oC , where 30 minutes at 44 has the same effect in terms of loss of viability as 5 minutes at 46oC; by 48oC viability has been significantly reduced to a population of persister cells.
Does anyone know of any other examples of this sort of in the existing literature; of course it is obvious that all bacteria have an upper temperature limit for viability, but what I'm wondering is what mechanism (what key protein degrades? membrane collapse) controls this?
Hi Hani
Thanks for your message. I have not tried to work out the cardinal temperature range that the organism grows at personally, although this might be historical data that we have in the lab. What I did do was to expose the organism to 40, 42, 44, 46, 48 and 50 for 2, 5, 10, 15 and 30 minutes. What i found is that you don't get significant drops in viability at 40 and 42 after 30 minutes, but after 10 minutes at 44 you start to see a drop. This drop becomes more rapid as you increase the temperature to 46, and by 48 and 50 the drop trend becomes the same. I have been digging through the literature when I found this:
http://link.springer.com/article/10.1023/A:1006840623763
and this:
http://www.sciencedirect.com/science/article/pii/S000398610500072X
From the whole paper in the top link, and the viability data in the second paper, it seems that thykaloid membrane stability starts to collapse at 42-44oC, and that you get a sharp irreversible phase change at 45-46oC that leads to necrosis.
I found the top paper after I sent out this message, but it seems to answer my problem. Do you have any thoughts on those conclusions?
Toby
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