Genetics, Vol 147, 991-1001, Copyright © 1997


INVESTIGATIONS

A Genetic Strategy to Demonstrate the Occurrence of Spontaneous Mutations in Nondividing Cells Within Colonies of Escherichia coli

M. Reddy and J. Gowrishankar
Centre for Cellular and Molecular Biology, Hyderabad 500 007, India

A genetic strategy was designed to examine the occurrence of mutations in stationary-phase populations. In this strategy, a parental population of cells is able to survive under both permissive and restrictive conditions whereas mutants at a particular target locus exhibit a conditional-lethal phenotype. Thus, by growing the population to stationary phase under restrictive conditions and then shifting it to permissive conditions, mutations that had arisen in stationary phase can be studied without confounding effects caused by the occurrence of similar mutations during growth of the population. In two different applications of this strategy, we have studied the reversion to Lac(+) in stationary phase of several Lac(-) mutations in Escherichia coli. Our results indicate that a variety of spontaneous point mutations and deletions, particularly those that are sensitive to the mechanisms of replication slippage (for their generation) and methyl-directed mismatch repair (for their correction), can arise in nondividing populations of cells within a colony. The frequency of their occurrence was also elevated in mutS strains, which are defective in such mismatch repair. These data have relevance to the ongoing debate on adaptive or directed mutations in bacteria.


This article has been cited by other articles:


Home page
GeneticsHome page
S. M. Bharatan, M. Reddy, and J. Gowrishankar
Distinct Signatures for Mutator Sensitivity of lacZ Reversions and for the Spectrum of lacI/lacO Forward Mutations on the Chromosome of Nondividing Escherichia coli
Genetics, February 1, 2004; 166(2): 681 - 692.
[Abstract] [Full Text] [PDF]


Home page
J. Bacteriol.Home page
L. SaiSree, M. Reddy, and J. Gowrishankar
lon Incompatibility Associated with Mutations Causing SOS Induction: Null uvrD Alleles Induce an SOS Response in Escherichia coli
J. Bacteriol., June 1, 2000; 182(11): 3151 - 3157.
[Abstract] [Full Text]


Home page
J. Bacteriol.Home page
M. Reddy and J. Gowrishankar
Characterization of the uup Locus and Its Role in Transposon Excisions and Tandem Repeat Deletions in Escherichia coli
J. Bacteriol., April 1, 2000; 182(7): 1978 - 1986.
[Abstract] [Full Text]


Home page
Proc. Natl. Acad. Sci. USAHome page
P. L. Foster
Sorting out mutation rates
PNAS, July 6, 1999; 96(14): 7617 - 7618.
[Full Text] [PDF]