Surviving bad times: E. coli's response to a switch from a rich to a poor medium

Supervisor:Fred Boogerd/Rodolfo Garcia (room G226e)

There are two projects. One deals with carbon, the other with nitrogen. The projects are related, but each one can be studied as a single MSc-project.

Carbon and Nitrogen are essential elements for all life forms.  A problem living organisms are confronted with as a fact of life is the ever changing environmental availability of nutrients, including C- and N-containing compounds. They have to deal with every possible nutritional status that lies somewhere in between feast and famine; periods of nutrient excess can be followed by periods of starvation. However, microorganisms have to endure nutrient limitation much more frequently than that they can enjoy nutritional affluence. In general, flexibility in the way cells can handle the variation in food supply seems essential for survival and reproduction.

In project I, you will study the transition from a rich to a poor carbon source, that is from a tasty sugar (glucose) to a sourish acid (acetate). A switch that requires a dramatic shift in metabolism. You will study this shift at the level of enzyme fluxes and metabolite concentrations. Metabolic pathways such glycolysis, citric acid and glyoxylate cycle and gluconeogenesis are involved. Besides wild type E. coli, several interesting mutants in carbon metabolism are available to further characterize the switch.

In project II, you will study the transition from a rich to a poor nitrogen source, that is from the preferred ammonium to the amino acid glutamine. A switch that requires redistribution of nitrogen among the two nitrogen-assimilating pathways. You will study this shift at the level of enzyme fluxes and metabolite concentrations. The two nitrogen pathways GS-GOGAT and GDH are involved. Besides wild type E. coli, several interesting mutants in nitrogen metabolism are available to further characterize the switch.