Limiting phosphorus may result in impaired growth and decreased glucose content in Escherichia coli MG1655

Abstract

Inorganic phosphate is an important source of phosphorus for Escherichia coli metabolism. In addition to carbon and nitrogen, the presence of these molecules within the bacterium’s environment contributes to its survival and growth. As such, extended periods of nutrient starvation results in metabolic and physiological changes to allow the organism to survive and adapt. Such a change is the activation of the stationary phase stress response primed by RpoS expression that results in glycogen accumulation. We hypothesized that the response occurs when phosphorus is limited to conserve metabolic energy in the form of glycogen as essential nutrients are limited. To determine the effects of phosphorus and nitrogen limitation on cellular growth and stationary phase glycogen accumulation of E. coli, MG1655 wild-type cells were subjected to nutrient limitation, and subsequent cellular glycogen quantification was attempted using a previously-established enzymatic glucose assay. Bacterial growth curve analysis showed that phosphorus-limiting conditions significantly impaired growth across all growth phases compared to non-limiting conditions and nitrogen-limiting conditions. Likewise, cellular glucose levels quantified after amyloglucosidase/hexokinase treatment may indicate a reduction of cellular glucose levels when phosphorus was limited compared to non-limiting conditions. Similarly, a possible reduction in cellular glucose levels relative to non-limiting conditions was observed in the nitrogen-limiting conditions but only when treated with amyloglucosidase. Altogether, the results of the investigation did not implicate any conclusive findings between phosphorus or nitrogen limitation and changes in cellular glycogen levels, but rather suggested that limiting phosphorus may lead to a reduction in bacterial growth and cellular glucose levels.