E. coli K12, the prokaryotic wimp
is a coliform bacterium that is a normal component of the human
intestinal flora, and is ordinarily
not a dangerous organism. The
K12 and related strains of E. coli
used in molecular cloning have been modified so that they are able to survive in culture only under
very specific conditions, and unable
survive at all in the human gut.
Municipal water sources are routinely tested for the
presence of "coliform"
(rod-shaped) bacteria, which would indicate
possible contamination with human or animal faecal material. Recent
cases of E. coli
contamination stem from "natural" pathogenic strains of E. coli that have found their way
into public water sources through improper sterilization or filtration.
Figure © 1991 by Gonick
& Wheelis, The Cartoon Guide to Genetics;
text © 2009
Steven M. Carr