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Theta‐type DNA replication stimulates homologous recombination in the Bacillus subtilis chromosome
Author(s) -
MorelDeville Françoise,
Ehrlich S. Dusko
Publication year - 1996
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1996.398936.x
Subject(s) - biology , bacillus subtilis , homologous recombination , homologous chromosome , genetics , recombination , chromosome , dna replication , dna , ploidy , gene , bacteria
To test the effects of theta‐type replication on homologous DNA recombination, we integrated in the chromosome of Bacillus subtilis a structure comprising a conditional replication region and direct repeats of ∼ 4 kb. The replicon was derived from a broad‐host‐range plasmid, pAMβ1, which replicates by a unidirectional theta mechanism and is thermosensitive. The direct repeats were derived from plasmid pBR322 and flanked the chloramphenicol‐resistance gene of plasmid pC194. Recombination between the repeats could therefore lead to a loss of the resistance gene or the appearance of additional repeats. The integrated replicon was active at the permissive temperature, and ∼ 25% of the integrated plasmids could be isolated as Y‐shaped molecules after restriction, having a branch at the replication origin. Replicon activity stimulated recombination four‐ to fivefold, as estimated from the proportion of chloramphenicol‐sensitive cells at the restrictive and permissive temperature, and also led to the appearance of additional direct repeats. We conclude that theta‐type replication stimulates homologous recombination and suggest that many or even most recombination events between long homologous sequences present in a bacterial genome may be the consequence of DNA replication.