Bacterial glycogen provides short-term benefits in changing environments

Abstract

6Changing nutritional conditions challenge microbes and shape their evolutionary 1 7 optimization. Here we investigated the role of glycogen in dynamic physiological adaptation 1 8of Escherichia coli to fluctuating nutrients following carbon starvation using real-time 1 9 metabolomics. We found significant metabolic activity remaining after the depletion of 2 0 environmental glucose that was linked to a rapid utilization of intracellular glycogen. 2 1 Glycogen was depleted by 80% within minutes of glucose starvation and similarly 2 2 replenished within minutes of glucose availability. These fast timescales of glycogen 2 3 utilization correspond to the short-term benefits that glycogen provided to cells undergoing 2 4 various physiological transitions. Cells capable of utilizing glycogen exhibited shorter lag 2 5times than glycogen mutants when starved between different carbon sources. The ability to 2 6 2 utilize glycogen was also important for the transition between planktonic and biofilm 2 7 lifestyles and enabled increased glucose uptake during pulses of limited glucose availability. 8While wild-type and mutant strains exhibited comparable growth rates in steady 2 9 environments, mutants deficient in glycogen utilization grew more poorly in environments 3 0 that fluctuated on minute-scales between carbon availability and starvation. Altogether, these 3 1 results highlight an underappreciated role of glycogen to rapidly provide carbon and energy in 3 2 changing environments, thereby increasing survival and competition capabilities in 3 3 fluctuating and nutrient poor conditions. 3 4 3 5