The transition from exponential to stationary phase growth in bacteria heralds extensive changes in biochemical, macromolecular, morphological and physiological properties. Stationary phase conditions in the laboratory may accurately reflect predominant conditions in the environment, where the unique properties of stationary phase cells are probably critical for competition and survival. Current evidence suggests that alterations in the pattern of gene expression, mediated via the effects of a few global regulatory factors, program these extensive changes. Glycogen (a-1,4 glucan with a-1,6 branches) biosynthesis is transcriptionally activated during early stationary phase in Escherichia coli. Our recent analysis of glycogen-overproducing mutants indicates that a previously uncharacterized regulatory system controls glycogen synthesis. This project is testing the hypothesis that the pleiotropic transposon-insertion mutation, TR1- 5, disrupts a component of a novel global regulatory system. The mutated gene is being sequenced and the mechanism of its effects on the expression of glycogen biosynthesis genes (glg) and other E. coli genes will be studied to elucidate its potential role in stationary phase adaptation. Although a-1,4 glucans are the predominant biological storage compounds and are important industrial products, the biological function of bacterial glycogen has not been rigorously established. Therefore, this project will also address the biological function of glycogen using survival and recovery experiments conducted with isogenic glycogen mutants. %%% This research is expected to provide information useful in achieving maximum gene expression in bacteria growing in industrial fermentors.
