Isolation and mapping of Escherichia coli mutations conferring resistance to division inhibition protein DicB.

Temperature-sensitive dicA mutants of Escherichia coli, dicA1(Ts), are blocked for cell division, owing to derepressed expression of a division inhibition gene, dicB. We isolated mutants which survived a high temperature in the dicA1 background and which survived induced expression of dicB carried by a high-copy-number plasmid. Most of the mutations conferred very slow growth on the cells. Two were mapped to the 90-min cluster of genes involved in translation and transcription, in or very close to gene rpoB. The majority of the other mutations were found to cause variable degrees of minicell formation and to map within or very close to the minB locus. Contrary to these mutations, the canonical min-1 mutation did not confer resistance to DicB.