lon transcriptional regulation of genes necessary for capsular polysaccharide synthesis in Escherichia coli K-12

Abstract

It has previously been observed that Escherichia coli lon mutations increase the levels of enzymes involved in the synthesis of colanic acid capsular polysaccharide (A. Markovitz, p. 415-462, in I. Sutherland, ed., Surface Carbohydrates of the Prokaryotic Cell, 1977). To determine how lon regulates these enzymes, we have isolated, mapped, and characterized lac operon and lac protein fusions to genes necessary for capsule synthesis by the Mu d(lac Amp) in vivo fusion technique of Casadaban and Cohen (M. J. Casadaban and S. N. Cohen, Proc. Natl. Acad. Sci. U.S.A. 76:4530-4533, 1979). At least five genes have been identified which share a common pattern of regulation: they are transcribed at low levels in lon+ strains and at significantly higher levels in lon strains. These genes are located in a cluster close to udk at 45 min on the E. coli map; we have named these genes cpsA, B, C, D, and E. An additional locus, cpsF, located at 90 min, is regulated in a similar manner to cpsA to E but is not essential for colanic acid synthesis. Similar studies on the transcriptional regulation of fusions in the gal and manA operons, also necessary for colanic acid synthesis, do not show significant regulation by the lon locus. Therefore, the regulatory system described here does not extend to all genes in the colanic acid synthesis pathway.