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Metabolite Sequestration Enables Rapid Recovery from Fatty Acid Depletion in Escherichia coli.

ABSTRACT: Microbes adapt their metabolism to take advantage of nutrients in their environment. Such adaptations control specific metabolic pathways to match energetic demands with nutrient availability. Upon depletion of nutrients, rapid pathway recovery is key to release cellular resources required for survival under the new nutritional conditions. Yet, little is known about the regulatory strategies that microbes employ to accelerate pathway recovery in response to nutrient depletion. Using the fatty acid catabolic pathway in Escherichia coli, here, we show that fast recovery can be achieved by rapid release of a transcriptional regulator from a metabolite-sequestered complex. With a combination of mathematical modeling and experiments, we show that recovery dynamics depend critically on the rate of metabolite consumption and the exposure time to nutrients. We constructed strains with rewired transcriptional regulatory architectures that highlight the metabolic benefits of negative autoregulation over constitutive and positive autoregulation. Our results have wide-ranging implications for our understanding of metabolic adaptations, as well as for guiding the design of gene circuitry for synthetic biology and metabolic engineering.IMPORTANCE Rapid metabolic recovery during nutrient shift is critical to microbial survival, cell fitness, and competition among microbiota, yet little is known about the regulatory mechanisms of rapid metabolic recovery. This work demonstrates a previously unknown mechanism where rapid release of a transcriptional regulator from a metabolite-sequestered complex enables fast recovery to nutrient depletion. The work identified key regulatory architectures and parameters that control the speed of recovery, with wide-ranging implications for the understanding of metabolic adaptations as well as synthetic biology and metabolic engineering.

SUBMITTER: Hartline CJ

PROVIDER: S-EPMC7078478 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Metabolite Sequestration Enables Rapid Recovery from Fatty Acid Depletion in Escherichia coli.

Hartline Christopher J CJ Mannan Ahmad A AA Liu Di D Zhang Fuzhong F Oyarzún Diego A DA

mBio 20200317 2

Microbes adapt their metabolism to take advantage of nutrients in their environment. Such adaptations control specific metabolic pathways to match energetic demands with nutrient availability. Upon depletion of nutrients, rapid pathway recovery is key to release cellular resources required for survival under the new nutritional conditions. Yet, little is known about the regulatory strategies that microbes employ to accelerate pathway recovery in response to nutrient depletion. Using the fatty ac ...[more]

PMID: 32184249

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Project description:BACKGROUND: Many E. coli genes show pH-dependent expression during logarithmic growth in acid (pH 5-6) or in base (pH 8-9). The effect of rapid pH change, however, has rarely been tested. Rapid acid treatment could distinguish between genes responding to external pH, and genes responding to cytoplasmic acidification, which occurs transiently following rapid external acidification. It could reveal previously unknown acid-stress genes whose effects are transient, as well as show which acid-stress genes have a delayed response. RESULTS: Microarray hybridization was employed to observe the global gene expression of E. coli K-12 W3110 following rapid acidification of the external medium, from pH 7.6 to pH 5.5. Fluorimetric observation of pH-dependent tetR-YFP showed that rapid external acidification led to a half-unit drop in cytoplasmic pH (from pH 7.6 to pH 6.4) which began to recover within 20 s. Following acid treatment, 630 genes were up-regulated and 586 genes were down-regulated. Up-regulated genes included amino-acid decarboxylases (cadA, adiY, gadA), succinate dehydrogenase (sdhABCD), biofilm-associated genes (bdm, gatAB, and ymgABC), and the Gad, Fur and Rcs regulons. Genes with response patterns consistent with cytoplasmic acid stress were revealed by addition of benzoate, a membrane-permeant acid that permanently depresses cytoplasmic pH without affecting external pH. Several genes (yagU, ygiN, yjeI, and yneI) were up-regulated specifically by external acidification, while other genes (fimB, ygaC, yhcN, yhjX, ymgABC, yodA) presented a benzoate response consistent with cytoplasmic pH stress. Other genes (the nuo operon for NADH dehydrogenase I, and the HslUV protease) showed delayed up-regulation by acid, with expression rising by 10 min following the acid shift. CONCLUSION: Transcriptomic profiling of E. coli K-12 distinguished three different classes of change in gene expression following rapid acid treatment: up-regulation with or without recovery, and delayed response to acid. For eight genes showing acid response and recovery (fimB, ygaC, yhcN, yhjX, ymgABC, yodA), responses to the permeant acid benzoate revealed expression patterns consistent with sensing of cytoplasmic pH. The delayed acid response of nuo genes shows that NADH dehydrogenase I is probably induced as a secondary result of acid-associated metabolism, not as a direct response to cytoplasmic acidification.

Project description:Comparative analysis of changes in gene and protein expression and fatty acid profiles between Escherichia coli K-12 MG1655 ΔfadD ΔaraBAD expressing an acyl-acyl carrier protein thioesterase from Umbellularia californica (BTE) or a non-functional mutant thioesterase (BTE-H204A) to determine the functional basis for losses in cell viability, membrane integrity, or other stresses and metabolic perturbations that may be present. New hypotheses obtained from the study will assist in metabolic engineering efforts of improved strains exhibiting higher fatty acid yields and productivities. Cultures of fatty acid overproducing (BTE-expressing) and negative control (non-functional BTE-H204A-expressing) strains of Escherichia coli K-12 MG1655 delta-fadD delta-araBAD (deficient in beta-oxidation and L-arabinose catabolism) were sampled under two different sets of media/induction/antibiotic conditions. These conditions were shake flasks at 37C, 250 rpm shaking, in EZ rich defined medium supplemented with 0.2% glucose and 0.01 mM biotin (EZglu), and in fermentors at 37C with controlled air sparging, agitation, and pH in EZ rich defined medium supplemented with 0.4% glycerol and 0.01 mM biotin (EZgly). Two strains were analyzed in the EZglu experiment, the background strain harboring either pTrc99A-BTE (fatty acid overproducing) or pTrc99A-BTE-H204A (control phenotype). Three strains were analyzed in the EZgly experiment, with the background strain haboring either pBAD35-BTE and pBAD33 (fatty acid overproducing), pBAD35-BTE and pBAD33-ACC (fatty acid overproducing, ACC are the 4 subunits of E. coli K-12 acetyl-CoA carboxylase expressed as an artificial operon accDABC in plasmid pBAD33), and pBAD35-BTE-H204A and pBAD33 (control phenotype). RNA was extracted from harvested cell pellets from biological triplicates (EZglu) or biological duplicates (EZgly) of each strain at three different sampling times as defined in each sample description. Due to a hybridization or scanning problem, biological duplicates rather than triplicates were analyzed at the mid-stationary phase sampling point in the EZglu experiment for the control strain harboring pTrc99A-BTE-H204A. Multiple technical replicates at either the hybridization or sample level were analyzed from the biological duplicates of the fermentor experiment. The form of technical replicate (sample or hybridization) is specified in each EZgly sample description.

Dataset Information

Metabolite Sequestration Enables Rapid Recovery from Fatty Acid Depletion in Escherichia coli.

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Metabolite Sequestration Enables Rapid Recovery from Fatty Acid Depletion in Escherichia coli.

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