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Genome‐wide hypermutation in a subpopulation of stationary‐phase cells underlies recombination‐dependent adaptive mutation
Author(s) -
Torkelson Joel,
Harris Reuben S.,
Lombardo MaryJane,
Nagendran Jayan,
Thulin Carl,
Rosenberg Susan M.
Publication year - 1997
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/16.11.3303
Subject(s) - somatic hypermutation , biology , adaptive mutation , replicon , genetics , mutation , gene , mutagenesis , plasmid , genome , population , demography , b cell , sociology , antibody
Stationary‐phase mutation in microbes can produce selected (‘adaptive’) mutants preferentially. In one system, this occurs via a distinct, recombination‐dependent mechanism. Two points of controversy have surrounded these adaptive reversions of an Escherichia coli lac mutation. First, are the mutations directed preferentially to the selected gene in a Lamarckian manner? Second, is the adaptive mutation mechanism specific to the F plasmid replicon carrying lac ? We report that lac adaptive mutations are associated with hypermutation in unselected genes, in all replicons in the cell. The associated mutations have a similar sequence spectrum to the adaptive reversions. Thus, the adaptive mutagenesis mechanism is not directed to the lac genes, in a Lamarckian manner, nor to the F′ replicon carrying lac . Hypermutation was not found in non‐revertants exposed to selection. Therefore, the genome‐wide hypermutation underlying adaptive mutation occurs in a differentiated subpopulation. The existence of mutable subpopulations in non‐growing cells is important in bacterial evolution and could be relevant to the somatic mutations that give rise to cancers in multicellular organisms.