[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Reverse-engineering the T. rex genome



Phillip Bigelow wrote:

> Apparently, for crocs and gators, the immune response (and
> other defenses) defeat the microorganism (otherwise the
> disease wouldn't be characterized as an "avian" disease.
> 
> Maybe I'm bogging myself down in semantics, but isn't the
> animal's unique immune response (or lack there-of), and its
> other unique defenses to infection (or lack there-of)
> predisposed by its genes?
> 
> If it isn't predisposed by genes, then why do only birds
> get this infection?


I'd pretty much agree with Dann here.  The microbe in question is probably 
adapted to surviving (and replicating) within a certain optimal temperature 
range.  The physiology of birds (as endotherms) maintains a high and constant 
body temperature.  Crocs are ectothermic, and are therefore prone to 
fluctuations in body temp.  If the microbe isn't at its peak metabolic 
performance, then it's more susceptible to being brought down by the host's 
defenses.  


The bacterium Escherichia_ coli_, which thrives in the human gut (mostly 
harmless, but with certain strains being highly pathogenic), has an optimal 
growth temp of around 37C.  Why 37C?  Because that is the normal human body 
temp.  _E. coli_ doesn't like cool temps, and will go into "cold stress" mode 
at around 15C.



Cheers

Tim