Expression of the adenylate cyclase gene during cell elongation in Escherichia coli K-12.

Expression of the adenylate cyclase gene (cya) in synchronized Escherichia coli cells was investigated by using the cya-lacZ protein and operon fusion plasmids. The regulation of cya expression during the cell cycle is characterized as follows: cya is expressed during cell elongation; expression is repressed during cell division; regulation is exerted at the transcriptional level. To test cya expression during cell elongation, we constructed a plasmid (pLCR1) in which the lacUV5 promoter operator was fused to the structural gene of cya and investigated the effect of cya expression by isopropyl-beta-D-thiogalactopyranoside (IPTG) on the cell division of cells containing pLCR1. By the addition of IPTG, cell division was inhibited and filaments were formed. Such an inhibitory effect was antagonized by adding cyclic GMP to the culture medium and was not observed in the crp mutant.