Amplification of mutator cells in a population as a result of horizontal transfer.
Mutator cells that lack the mismatch repair system (MMR(-)) occur at rates of 10(-5) or less in laboratory populations started from wild-type cells. We show that after selection for recombinants in an interspecies mating between Salmonella enterica serovar Typhimurium and Escherichia coli, the percentage of MMR(-) cells rises to several percent of the recombinant population, and after a second successive mating and selection, greater than 95% of the recombinants are MMR(-). Coupling a single cross and selection with either mutagenesis or selection for spontaneous mutants also results in a dramatic increase in MMR(-) cells. We discuss how horizontal transfer can result in mutator strains during adaptive evolution.
Funchain
P
P
Department of Microbiology and Molecular Genetics, University of California, Los Angeles, California 90095, USA.
Yeung
A
A
Stewart
J
J
Clendenin
W M
WM
Miller
J H
JH
D020137:Base Pair Mismatch; D003227:Conjugation, Genetic; D003433:Crosses, Genetic; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics*; D022761:Gene Transfer, Horizontal; D010641:Phenotype; D019779:Salmonella enterica / Q000166:cytology / Q000235:genetics*