Thanks to those who replied to my inquiry on the history
of experimentation on the fitness consequences of increased/decreased
mutation rates in bacteria. The reference I'm sure I had in mind
was provided by Barry Hall, who (along with others) noted that
fitness was increased with increased mutation rates, not decreased
by decreased mutation rates as I had (mis)remembered and posted.
The citation that follows contains references to the genetic control
of mutation rate, including reduced mutation rate in T4. Several
people who replied to my post referred to the work in T4. I
won't post those references; they're available in the key
Cox, Edward C. & Gibson, Thomas C. (1974) Selection for high
mutation rates in chemostats. Genetics 77:169-184.
"Competition experiments in chemostats show that mutator
populations of Escherichia coli are more fit than wild type. The
increased fitness can be explained by the appearance of new mutants
better adapted to the chemostat environment. Fitness values vary
between chemostats and are strongly correlated (P<0.001) with
fluctuations in population density."
Thanks again to everyone who replied.
Department of Biochemistry and College of Forest Resources
University of Washington, Seattle
toby at u.washington.edu