Transcriptional analysis of the sigA and sigB genes of Brevibacterium lactofermentum

Transcription of the sigA</it> and sigB</it> genes of Brevibacterium lactofermentum</it>, encoding the principal sigma factors of RNA polymerase, has been investigated by Northern blot and primer extension analysis. Northern hybridizations revealed that sigA</it> is transcribed as a monocistronic mRNA of 1.7 kb and sigB</it> gives two transcripts of 1.1 and 1.5 kb. Similar transcription patterns of sigA</it> and sigB</it> 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</it> RNA showed that the sigA</it> and sigB</it> 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</it> and sigB</it> promoter regions provided evidence for highly conserved sequences in both of them.