Aggregation of Escherichia coli proteins during stationary phase depends on glucose and oxygen availability

In natural environments, bacteria are often challenged by nutrient starvation and other stresses. As a consequence, cell growth is arrested and bacteria enter stationary phase. In this report, we demonstrate that during stationary phase, Escherichia coli cells accumulate aggregates of misfolded proteins and complexes of Dps (starvation-induced protein) with chromosomal DNA. We found that the formation of multicomponent protein aggregates and insoluble Dps-DNA complexes depended on growth conditions and was influenced by the availability of oxygen and glucose in a medium. Aerobic stationary cells grown in unbuffered medium supplemented with glucose contained insoluble Dps-DNA, whereas multicomponent protein aggregates were accumulated under glucose starvation. On the contrary, under oxygen depletion, Dps-DNA complexes were formed in the absence of glucose, whereas multicomponent protein aggregates appeared in the presence of glucose. The mechanisms responsible for this phenomenon remain to be elucidated; however, we demonstrated that in MOPS-buffered cultures the level of insoluble Dps and protein aggregates was decreased.