Persistant phenotypic differences (serial subculture)?

James Graham graham at biodec.wustl.edu
Thu Jun 13 16:27:55 EST 1996

> I would also think that it could be connected with mutation events.
> Decades ago I remember a discussion on a conference about such a problem.
> The outcome was like that after a long run of a chemostate (several tenth
> of generations) there should be a remarkable difference between the last
> culture and the inoculum. The pessimists should stop work with
> chemostates if they use it in a manner to produce an "equal product" for
> their research needs. The optimists argue that you could always identify
> e.g. E.coli as E.coli during the chemostate run. At least the differences
> caused by different dilutions suggest a solution within the direction of
> mutation to me.

In contrast to "several tens of generations" of chemostat growth, the 
variation between identical log phase batch cultures inoculated from 
different sources of the same strain (eg. colony vs. broth) occurs apparently 
among the majority of cells after only 4 or 5 generations. No feasible 
mutation rate could possibly account for such extensive phenotypic difference.

Clearly, this aspect of microbial physiology is vastly under-appreciated
considering it is readily observable in daily laboratory work. (Only
one potential relevant source of references has so far been suggested.)

Anyone else seen anything? Other examples of this?

J. Graham PhD 
Biology Department 
Washington University of St. Louis 

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