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J. Bacteriol., 02 1996, 951-960, Vol 178, No. 4
S Ferrer, MB Viejo, JF Guasch, J Enfedaque and M Regue
Bacteriocin 28b production is induced by mitomycin in wild-type Serratia
marcescens 2170 but not in Escherichia coli harboring the bacteriocin 28b
structural gene (bss). Studies with a bss-lacZ transcriptional fusion
showed that mitomycin increased the level of bss gene transcription in S.
marcescens but not in the E. coli background. A S. marcescens Tn5 insertion
mutant was obtained (S. marcescens 2170 reg::Tn5) whose bacteriocin 28b
production and bss gene transcription were not increased by mitomycin
treatment. Cloning and DNA sequencing of the mutated region showed that the
Tn5 insertion was flanked by an SOS box sequence and three genes that are
probably cotranscribed (regA, regB, and regC). These three genes had
homology to phage holins, phage lysozymes, and the Ogr transcriptional
activator of P2 and related bacteriophages, respectively. Recombinant
plasmid containing this wild- type DNA region complemented the reg::Tn5
regulatory mutant. A transcriptional fusion between a 157-bp DNA fragment,
containing the apparent SOS box upstream of the regA gene, and the cat gene
showed increased chloramphenicol acetyltransferase activity upon mitomycin
treatment. Upstream of the bss gene, a sequence similar to the consensus
sequence proposed to bind Ogr protein was found, but no sequence similar to
an SOS box was detected. Our results suggest that transcriptional induction
of bacteriocin 28b upon mitomycin treatment is mediated by the regC gene
whose own transcription would be LexA dependent.
Copyright © 1996, American Society for Microbiology
Genetic evidence for an activator required for induction of colicin- like bacteriocin 28b production in Serratia marcescens by DNA-damaging agents
Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Barcelona, Spain.
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