GENETIC AND TRANSCRIPTIONAL ORGANIZATION OF THE BACILLUS-SUBTILIS SPC-ALPHA REGION

We used chromosomal walking methods to isolate a 10.8-kb region from t he major ribosomal protein (r-protein) gene cluster of Bacillus subtil is (Bs). The gene order in this region, given by gene product, was r-p roteins L14-L24-L5-S14-S8-L6-L18-S5-L30-L15-SecY-adenylate kinase (Adk )-methionine aminopeptidase (Map)-initiation factor 1 (IF1)-L36-S13-S1 1-alpha subunit of RNA polymerase-L17. The region cloned, therefore, c ontains the homologues for the last three genes of the Escherichia col i (Ec) S10 operon, together with entire spc and alpha operons. This Bs organization differs from the corresponding region in Ec by the inclu sion of the genes encoding Adk, Map and IF1 between the genes encoding SecY and L36. Plasmid integration experiments indicated that all 22 g enes comprise a single large transcriptional unit controlled from a ma jor promoter which lies upstream from the gene encoding r-protein L16. Promoter probe experiments located lesser activities internal to this large transcriptional unit, the secY and map promoters. The secY prom oter region (psecY) contained two activities, each principally functio ning in the stationary growth phase when high protein export is requir ed. Thus, the Bs S10-spc-alpha region differs from its Ec counterpart in both genetic and transcriptional organization. Given this differenc e in transcriptional organization, the mechanisms coordinating express ion of the translational apparatus are also likely to differ between E c and Bs.