Abstract

Evolution Shapes Differences in Bacterial Response to Nutrient Starvation

Volker Behrends, Lecturer, Roehampton University

Getting the most out of available nutrients is one of the key challenges in nature. At the same time, organisms have to maintain a certain amount of physiological plasticity to respond if nutrient availability changes. As metabolic pathways need to integrate different nutrient inputs simultaneously, we were interested in how this apparent paradox of optimised growth and optimised flexibility is handled at metabolic and protein level across species. We investigated nitrogen limitation and starvation in Escherichia coli and Mycobacterium smegmatis by transcriptiomic, proteomic and NMR- and LC/MS-based metabolic profiling. By dynamically monitoring responses to changing nitrogen availability we were able to study the systems behaviour and signalling hierarchies. Growth of E. coli was fast, strictly correlated to extracellular nitrogen availability and characterized by differentially regulated overflow metabolism of acetate and a-ketoglutarate (among others) during active growth and starvation, respectively. In contrast, M. smegmatis accumulated ‘capacitator’ metabolites to buffer extracellular shortages of carbon or nitrogen. Additionally, we identified hierarchies of key proteomic and metabolic regulators controlling short- and long-term limitation response. The two bacteria exhibited two fundamentally different coping strategies. While E. coli employs a fast growth, feast-or-famine approach, M. smegmatis synthesises metabolites to be used up in times of limitation.