Genetic analysis of a class of polymyxin resistant partial revertants of stage O sporulation mutants of Bacillus subtilis: Map of the chromosome region near the origin of replication

A group of extracistronic mutations restored polymyxin resistance to stage O sporulation mutants of Bacillus subtilis, as well as resistance to antibiotic from the wild type sporulating strain, and to phages Φ2 and Φ15, without restoring the ability to sporulate.

Abstract

A group of extracistronic mutations restored polymyxin resistance to stage O sporulation mutants of Bacillus subtilis, as well as resistance to antibioticfrom the wild type sporulating strain, and to phages Φ2 and Φ15,without restoring the ability to sporulate.The spoOA mutants containing these partial revertant mutations fell into two major classes: Those that grew well in minimal media and produced little antibiotic;and those that grew poorly and produced high levels of antibiotic.The partial revertant mutations were located near the origin of replication of the chromosome on the genetic map,in a locus called abrB.A detailed map of this region was constructed using data from two and three factor transduction and transformation crosses.The following order of markers was obtained: purA 16-spo-CM1-novA1-gua-1-(dnaH151-ts8132)-recG13-abrB-pac-tms-26-lysS-cysA14. The abrBlocus was separated by at least 50% recombination in transformation from the known loci on either side of it.Similar partial revertant mutations from other laboratories (cpsX, abs, and tol markers)also mapped at the abrB locus. The mutations at this locus were closely linked by transformation (recombination index <0.1 in most cases)suggesting that they comprise a single gene.