Laboratory K-12 colonizing our guts?

[ChenHA]

David F. Spencer wrote:

> 
> E.coli K-12 was the first of the primary E. coli isolates (1922, from 
> the stool of a diptheria patient).
> Here is a section from a good summary of E. coli, including K-12, taken 
> from:
> 
> http://www.epa.gov/oppt/biotech/pubs/fra/fra004.htm

Interesting site.  It doesn't however deal with other coli strains like 
BL21 which is commonly used for protein expression.  Is there 
information on the B strain?