Phosphoenolpyruvate:carbohydrate phosphotransferase systems of bacteria.

SUMMARY: It was investigated whether Escherichia coli cultured in a glucose-limited chemostat is able to grow with a series of sugars whose utilization is normally repressed during batch growth with glucose. Cells growing at dilution rates of 0·2, 0·3 and 0·6 h-1 were able to immediately utilize and grow with fructose mannose, maltose and ribose. Galactose was transported instantaneously but growth started only after a considerable lag. Arabinose was the only sugar tested which was neither transported nor utilized immediately. The results give experimental evidence that in vivo catabolite repression by glucose is absent at the very low glucose concentrations present in chemostat culture. Additionally, the results demonstrate that chemostat-grown cells of E. coli are able to substitute glucose as a carbon and energy source by several other sugars with no lag period.

Is Escherichia coli growing in glucose-limited chemostat culture able to utilize other sugars without lag?

crr mutants of Salmonella typhimurium are thought to be defective in the regulation of adenylate cyclase and a number of transport systems by the phosphoenolpyruvate-dependent sugar phosphotransferase system, crr mutants are also defective in the enzymatic activity of factor IIIGlc (IIIGlc), a protein component of the phosphotransferase system involved in glucose transport. Therefore, it has been proposed that IIIGlc is the primary effector of phosphotransferase system-mediated regulation of cell metabolism. We characterized crr mutants with respect to the presence and function of IIIGlc by using an immunochemical approach. All of the crr mutants tested had low (0 to 30%) levels of IIIGlc compared with wild-type cells, as determined by rocket immunoelectrophoresis. The IIIGlc isolated from one crr mutant was investigated in more detail and showed abnormal aggregation behavior, which indicated a structural change in the protein. These results supported the hypothesis that a crr mutation directly affects IIIGlc, probably by altering the structural gene of IIIGlc. Several crr strains which appeared to be devoid of IIIGlc in immunoprecipitation assays were still capable of in vitro phosphorylation and transport of methyl alpha-glucoside. This phosphorylation activity was sensitive to specific anti-IIIGlc serum. Moreover, the membranes of crr mutants, as well as those of wild-type cells, contained a protein that reacted strongly with our anti-IIIGlc serum. We propose that S. typhimurium contains a membrane-bound form of IIIGlc which may be involved in phosphotransferase system activity.

Characterization of factor IIIGLc in catabolite repression-resistant (crr) mutants of Salmonella typhimurium.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2884%2980794-2

Genetic studies of the phs locus of Escherichia coli, a mutation causing pleiotropic lesions in metabolism and pH homeostasis

Carbohydrate utilization patterns and substrate preferences in Bacteroides thetaiotaomicron.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2880%2980567-9

Kathleen Brown

Papers

Mechanisms of 'inducer exclusion' by glucose.