Transcriptional analysis of the sigA and sigB genes of Brevibacterium lactofermentum.

Transcription of the sigA and sigB genes of Brevibacterium lactofermentum, encoding the principal sigma factors of RNA polymerase, has been investigated by Northern blot and primer extension analysis. Northern hybridizations revealed that sigA is transcribed as a monocistronic mRNA of 1.7 kb and sigB gives two transcripts of 1.1 and 1.5 kb. Similar transcription patterns of sigA and sigB genes in nutrient-rich medium were observed; transcripts of both genes occurred simultaneously throughout the exponential growth phase and decayed clearly when the stationary phase was reached. Primer extension analysis of B. lactofermentum RNA showed that the sigA and sigB transcription initiation sites are located 17 bp and 24 bp upstream from the first nucleotide of the respective translation initiation codons. Alignment of the sigA and sigB promoter regions provided evidence for highly conserved sequences in both of them.