Genetic composition of the Bacillus subtilis SOS system

J Bacteriol. 2005 Nov;187(22):7655-66. doi: 10.1128/JB.187.22.7655-7666.2005.


The SOS response in bacteria includes a global transcriptional response to DNA damage. DNA damage is sensed by the highly conserved recombination protein RecA, which facilitates inactivation of the transcriptional repressor LexA. Inactivation of LexA causes induction (derepression) of genes of the LexA regulon, many of which are involved in DNA repair and survival after DNA damage. To identify potential RecA-LexA-regulated genes in Bacillus subtilis, we searched the genome for putative LexA binding sites within 300 bp upstream of the start codons of all annotated open reading frames. We found 62 genes that could be regulated by putative LexA binding sites. Using mobility shift assays, we found that LexA binds specifically to DNA in the regulatory regions of 54 of these genes, which are organized in 34 putative operons. Using DNA microarray analyses, we found that 33 of the genes with LexA binding sites exhibit RecA-dependent induction by both mitomycin C and UV radiation. Among these 33 SOS genes, there are 22 distinct LexA binding sites preceding 18 putative operons. Alignment of the distinct LexA binding sites reveals an expanded consensus sequence for the B. subtilis operator: 5'-CGAACATATGTTCG-3'. Although the number of genes controlled by RecA and LexA in B. subtilis is similar to that of Escherichia coli, only eight B. subtilis RecA-dependent SOS genes have homologous counterparts in E. coli.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 5' Flanking Region
  • Bacillus subtilis / genetics*
  • Bacillus subtilis / physiology
  • Bacterial Proteins / metabolism
  • Binding Sites / genetics
  • Computational Biology
  • Consensus Sequence
  • DNA Damage
  • DNA, Bacterial / metabolism
  • Electrophoretic Mobility Shift Assay
  • Escherichia coli / genetics
  • Mitomycin / toxicity
  • Oligonucleotide Array Sequence Analysis
  • Open Reading Frames
  • Operator Regions, Genetic
  • Operon
  • Protein Binding
  • SOS Response, Genetics / genetics*
  • SOS Response, Genetics / physiology
  • Sequence Homology, Amino Acid
  • Serine Endopeptidases / metabolism
  • Ultraviolet Rays


  • Bacterial Proteins
  • DNA, Bacterial
  • LexA protein, Bacteria
  • Mitomycin
  • Serine Endopeptidases