Analysis of cepA and other Bacteroides fragilis genes reveals a unique promoter structure

Abstract

There is little known about the sequences that mediate the initiation of transcription in Bacteroides fragilis, thus transcriptional start sites for 13 new genes were determined and a total of 23 promoter regions upstream of the start sites were aligned and similarities were noted. A region at about -7 contained a consensus sequence of TAnnTTTG and upstream in the region centered at about -33, another TTTG motif was found in the majority of promoters examined. Canonical, Escherichia coli, -10 and -35 consensus sequences were not readily apparent. Mutations within the -7 motif indicated the TTTG residues were essential since changes in this sequence reduced the promoter activity to that of a no promoter control in a chloramphenicol acetyl transferase transcriptional fusion model system. Additional fusion studies indicated that the -33 region was also necessary for full activity.