Isolation and characterization of Streptococcus cremoris Wg2-specific promoters.

By cloning MboI fragments in the promoter selection vector pGKV210, which replicates in Streptococcus lactis, Bacillus subtilis, and Escherichia coli and carries a promoterless chloramphenicol acetyltransferase gene, we obtained a number of fragments endowed with promoter activity, partly by direct selection for chloramphenicol resistance in S. lactis IL1403 and partly by selection in B. subtilis. Five fragments were sequenced, and the promoters were mapped with S1 nuclease. The promoters agreed with the E. coli promoter consensus and the B. subtilis vegetative sigma 43 promoter consensus. The promoters were preceded by an A + T-rich region (ranging from 64 to 78% A + T). S1 nuclease mapping data showed that the transcriptional start point in three of the fragments was at a TAG sequence 5 to 9 nucleotides downstream from the promoter. Three fragments carried an open reading frame preceded by a ribosome-binding site which can be recognized by E. coli, B. subtilis, and S. lactis ribosomes.