Transcription of glycolytic genes and operons in Bacillus subtilis: evidence for the presence of multiple levels of control of the gapA operon

Glycolysis is one of the main pathways of carbon catabolism in Bacillus sub tilis. Although the biochemical activity of glycolytic enzymes has been stu died in detail, no information about the expression of glycolytic genes has so far been available in this organism. Therefore, transcriptional analysi s of all glycolytic genes was performed. The genes cggR, gapA, pgk, tpi, pg m and eno, encoding the enzymes required for the interconversion of triose phosphates, are transcribed as a hexacistronic operon as demonstrated by No rthern analysis. This gapA operon is repressed by the regulator CggR. The p resence of sugars and amino acids synergistically results in the induction of the gapA operon. The transcriptional start site upstream of cggR was map ped by primer extension. Transcripts originating upstream of cggR are proce ssed near the 3' end of cggR. This endonucleolytic cleavage leads to differ ential stability of the resulting processing products: the monocistronic cg gR message is very rapidly degraded, whereas the mRNA species encoding glyc olytic enzymes exhibit much higher stability. An additional internal consti tutive promoter was identified upstream of pgk. Thus, gapA is the most stro ngly regulated gene of this operon. The pfk pyk operon encoding phosphofruc tokinase and pyruvate kinase is weakly induced by glucose. In contrast, the genes pgi and fbaA, coding for phosphoglucoisomerase and fructose-1,6-bisp hosphate aldolase, are constitutively expressed.