Dynamic fluctuations in a bacterial metabolic network

Abstract

The operation of the central metabolism is typically assumed to be deterministic, but dynamics and high connectivity of the metabolic network make it potentially prone to generating fluctuations. However, time-resolved measurements of metabolite levels in individual cells that are required to characterize such fluctuations remained a challenge, particularly in small bacterial cells. Here we use single-cell metabolite measurements based on Förster resonance energy transfer, combined with computer simulations, to explore the real-time dynamics of the metabolic network of Escherichia coli. We observe that steplike exposure of starved E. coli to glycolytic carbon sources elicits large periodic fluctuations in the intracellular concentration of pyruvate in individual cells. These fluctuations are consistent with predicted oscillatory dynamics of E. coli metabolic network, and they are primarily controlled by biochemical reactions around the pyruvate node. Our results further indicate that fluctuations in glycolysis propagate to other cellular processes, possibly leading to temporal heterogeneity of cellular states within a population.

Lighting up Pyruvate Metabolism in Saccharomyces cerevisiae by a Genetically Encoded Fluorescent Biosensor

“…This finding was consistent with considerable fluctuation in intracellular pyruvate levels observed in starved E. coli cells expressing a CFP-PdhR-YFP-based pyruvate sensor when exposed to glucose . Interestingly, fructose also exhibited a response curve similar to that of glucose, suggesting that S.…”

“…The result was discrepant from the early finding that the response curves of pyruvate and glucose matched in E. coli . This finding may be explained by the complex pyruvate transport system in yeast cells compared to that in E.…”

“…This property allows for the normalization of fluorescence intensity, which can help to eliminate interference from the expression level of the sensor proteins. , Recently, Bi and co-workers introduced a new genetically encoded biosensor employing the PdhR flanked by a cyan fluorescent protein (CFP) and a yellow fluorescent protein (YFP) for energy transfer, combined with computer simulations, to analyze the real-time dynamics of the metabolic network of E. coli . However, to date, no studies have been conducted to monitor and image the pyruvate metabolism in vivo in yeast.…”

Metabolic Oscillation Phenomena in Clostridia Species—A Review

“…The negative feedback loop leading to the oscillation was not caused by inhibition through the final product (butanol), as the authors showed by artificially increasing butanol levels in the reactor. The oscillation might be similar to oscillations observed in the glycolysis pathway in yeast or bacteria mediated by redox coenzyme couples (ATP/ADP and NADH/NAD) and via both intraand intercellular acetaldehyde [39,40].…”

Exogenous Glucose Interferes with Antimicrobial-Mediated ROS Accumulation and Bacterial Death

“…A test for the involvement of the TCA cycle focused on pyruvate, the end product of glycolysis. Even after knocking out pykF , the major gene responsible for production of pyruvate from glycolysis, 0.1% glucose still caused a 100- to 1,000-fold increase in survival during ciprofloxacin treatment (Figure S3B). These data indicate that glucose-mediated tolerance is maintained in the pykF mutant.…”