Physiological role of E.coli

[Arlin Stoltzfus]

Ivan Yu. Torshin wrote:
> 
> Hello, world !
> 
> While trying to elucidate (by reading) physiological role of several
> periplasmic enzymes from E.coli, a question arose:
> 
>     What are physiological functions of human E.coli ? What
> substances does it produce/'eat' ?

E. coli lives in the intestines of most mammals, and is also 
found in some other tetrapods, as well as some insects.  In 
humans, E. coli is an extremely minor component of the 
intestinal flora-- most intestinal microbes are anaerobic, 
and Bacteroides fragilis, the most common component, is 
about 2 or 3 orders of magnitude more dense than E. coli 
in colon contents.  You could probably find out more by 
posting your question to bionet.microbiology.

It may be a mistake to assume that E. coli has a "function" 
for humans.  E. coli may not benefit mammals at all.  How 
would mammals prevent it from living there, given that they 
are so generous in providing homes for other microbes?  And 
even if E. coli has a "function" for some mammals, it may 
be living in humans just because it can.  

That having been said, at least some E. coli strains synthesize 
vitamin K (don't ask me what that is, chemically).  Whether 
one wants to call this a "function" depends on the evolutionary 
history of this relationship, and how anthropocentrically one 
wishes to define "function". 

Arlin

-- 
Arlin Stoltzfus
Department of Biochemistry
Dalhousie University
Halifax, Nova Scotia B3H 4H7 CANADA
(email) arlin at is.dal.ca 
(phone) 902-494-3569 
(fax) 902-494-1355