Disruption of trehalose periplasmic recycling dysregulates cAMP-CRP signaling in Escherichia coli during stationary phase

Abstract

ABSTRACT Trehalose is an endogenously synthesized disaccharide that is broadly distributed in the biosphere. While recognized for its carbohydrate reserve and metabolic regulatory functions in yeast and some bacteria, trehalose’s metabolic roles in Escherichia coli are less well understood. Trehalose is generated intracellularly upon exposure to heat stress or osmotic stress and during stationary phase. Although trehalose is regarded primarily as an osmoprotectant and stress metabolite in E. coli , our investigation into the effects of disrupting normal trehalose metabolism during long-term batch culture incubation in Lennox Broth medium indicates a regulatory property of trehalose recycling under starvation stress. Disruption of the periplasmic trehalase (TreA) results in elevated resource scavenging and glucose starvation signaling, consistent with the loss of glucose flux through the glucose-specific phosphotransferase system (PTS). We postulate that trehalase-mediated catabolism of trehalose—transported into the periplasm during growth limitation in rich media—releases glucose that, when imported through the PTS, fine-tunes carbon starvation responses via cyclic AMP (cAMP)-CRP (cAMP receptor protein) signaling during stationary phase. The loss of trehalose cycling generates a pleiotropic phenotype of survival deficits in monoculture and fitness enhancements against wild-type cells in coculture experiments during the batch culture condition of Long-Term Stationary Phase (LTSP). Our model is supported by glucose analog supplementation and genetic interventions that modulate glucose starvation responses, allowing partial recovery of viability during LTSP. IMPORTANCE Survival during starvation hinges on the ability to manage intracellular energy reserves and to initiate appropriate metabolic responses to perturbations of such reserves. How Escherichia coli manage carbon storage systems under starvation stress, as well as transpose changes in intracellular metabolite levels into regulatory signals, is not well understood. Endogenous trehalose metabolism may be at the center of these processes, coupling carbon storage with carbon starvation responses. The coupled transport to the periplasm and subsequent hydrolysis of trehalose back to glucose for transport to the cytoplasm may function as a crucial metabolic signaling pathway. Although trehalose has been characterized as a stress protectant in E. coli , the disaccharide also functions as both an energy storage compound and a regulator of carbohydrate metabolism in fungi, plants, and other bacteria. Our research explores the metabolic regulatory properties of trehalose in E. coli and a potential mechanism by which the intracellular carbon pool is interconnected with regulatory circuits, enabling long-term survival.