A proxy is where you count on a relation to use one easily measured thing instead of
what you actually want to measure. Temperature can be used as a proxy for
growth only because in a limited range, it correlates with growth. But that range needs
to be known for each organism, and needs to be stated in the protocol, and it usually
isn't.
Clearly temperature is not linear with growth when you reach the heat shock
levels, or the boiling point. But the growth curve with respect to temperature is
a curve, and we pretend it is linear by taking our samples from a narrow range.
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Get a free science project every week! "http://scitoys.com/newsletter.html"On Wed, Apr 25, 2012 at 10:21 AM, Nathan McCorkle <nmz787@gmail.com> wrote:
But in chemistry reactions are directly related to temperature, so its not really a proxy
On Apr 25, 2012 1:14 PM, "Simon Quellen Field" <sfield@scitoys.com> wrote:--I'm not arguing with Cathal -- he's brilliant, and more knowledgeable than I amabout these things. But I can build an incubator that guarantees I will never heatshock my critters, without needing better than 2 or 3 degrees in accuracy. I justset the temp 4 degrees below the heat shock temperature, and measure the growthof the colony more directly, instead of using temperature as a proxy for growth.-------Get a free science project every week! "http://scitoys.com/newsletter.html"
On Tue, Apr 24, 2012 at 9:45 PM, Nathan McCorkle <nmz787@gmail.com> wrote:On Tue, Apr 24, 2012 at 12:54 PM, Simon Quellen Field
<sfield@scitoys.com> wrote:
> What you say is true, but it is not necessary.
>
> You are using temperature as a surrogate for something else you actually
> should be
> measuring instead, such as the number of organisms per unit volume, or the
> growth
> rate, or the amount of some metabolite exceeds a threshold.
>> Higher temperatures mean moreWhat Cathal is saying here is a combination of things, that the temp
>> reactions per second, meaning faster growth. However, any higher than
>> this ceiling, and heat-shock starts to get induced. While the cells will
>> survive, their gene expression profiles will change markedly.
effects the growth rate so you could look at colony size delta with
vision processing or cell density with a light meter, but gene
expression IS heat dependent... when free energy levels are over a
protein or ribozyme's threshold (whatever that may be), stuff can
happen in a marked way (i.e. HSPs)
--
Nathan McCorkle
Rochester Institute of Technology
College of Science, Biotechnology/Bioinformatics
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