Dataset Information

Regulation of metabolism in Escherichia coli during growth on mixtures of the non-glucose sugars: arabinose, lactose, and xylose.

ABSTRACT: Catabolite repression refers to the process where the metabolism of one sugar represses the genes involved in metabolizing another sugar. While glucose provides the canonical example, many other sugars are also known to induce catabolite repression. However, less is known about the mechanism for catabolite repression by these non-glucose sugars. In this work, we investigated the mechanism of catabolite repression in the bacterium Escherichia coli during growth on lactose, L-arabinose, and D-xylose. The metabolism of these sugars is regulated in a hierarchical manner, where lactose is the preferred sugar, followed by L-arabinose, and then D-xylose. Previously, the preferential utilization of L-arabinose over D-xylose was found to result from transcriptional crosstalk. However, others have proposed that cAMP governs the hierarchical regulation of many non-glucose sugars. We investigated whether lactose-induced repression of L-arabinose and D-xylose gene expression is due to transcriptional crosstalk or cAMP. Our results demonstrate that it is due to cAMP and not transcriptional crosstalk. In addition, we found that repression is reciprocal, where both L-arabinose and D-xylose also repress the lactose gene expression, albeit to a lesser extent and also through a mechanism involving cAMP. Collectively, the results further our understanding of metabolism during growth on multiple sugars.

SUBMITTER: Ammar EM

PROVIDER: S-EPMC5766520 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Regulation of metabolism in Escherichia coli during growth on mixtures of the non-glucose sugars: arabinose, lactose, and xylose.

Ammar Ehab M EM Wang Xiaoyi X Rao Christopher V CV

Scientific reports 20180112 1

Catabolite repression refers to the process where the metabolism of one sugar represses the genes involved in metabolizing another sugar. While glucose provides the canonical example, many other sugars are also known to induce catabolite repression. However, less is known about the mechanism for catabolite repression by these non-glucose sugars. In this work, we investigated the mechanism of catabolite repression in the bacterium Escherichia coli during growth on lactose, L-arabinose, and D-xylo ...[more]

PMID: 29330542

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Project description:UnlabelledGlucose is known to inhibit the transport and metabolism of many sugars in Escherichia coli. This mechanism leads to its preferential consumption. Far less is known about the preferential utilization of nonglucose sugars in E. coli. Two exceptions are l-arabinose and d-xylose. Previous studies have shown that l-arabinose inhibits d-xylose metabolism in Escherichia coli. This repression results from l-arabinose-bound AraC binding to the promoter of the d-xylose metabolic genes and inhibiting their expression. This mechanism, however, has not been explored in single cells. Both the l-arabinose and d-xylose utilization systems are known to exhibit a bimodal induction response to their cognate sugar, where mixed populations of cells either expressing the metabolic genes or not are observed at intermediate sugar concentrations. This suggests that l-arabinose can only inhibit d-xylose metabolism in l-arabinose-induced cells. To understand how cross talk between these systems affects their response, we investigated E. coli during growth on mixtures of l-arabinose and d-xylose at single-cell resolution. Our results showed that mixed, multimodal populations of l-arabinose- and d-xylose-induced cells occurred at intermediate sugar concentrations. We also found that d-xylose inhibited the expression of the l-arabinose metabolic genes and that this repression was due to XylR. These results demonstrate that a strict hierarchy does not exist between l-arabinose and d-xylose as previously thought. The results may also aid in the design of E. coli strains capable of simultaneous sugar consumption.ImportanceGlucose, d-xylose, and l-arabinose are the most abundant sugars in plant biomass. Developing efficient fermentation processes that convert these sugars into chemicals and fuels will require strains capable of coutilizing these sugars. Glucose has long been known to repress the expression of the l-arabinose and d-xylose metabolic genes in Escherichia coli. Recent studies found that l-arabinose also represses the expression of the d-xylose metabolic genes. In the present study, we found that d-xylose also represses the expression of the l-arabinose metabolic genes, leading to mixed populations of cells capable of utilizing l-arabinose and d-xylose. These results further our understanding of mixed-sugar utilization and may aid in strain design.

Dataset Information

Regulation of metabolism in Escherichia coli during growth on mixtures of the non-glucose sugars: arabinose, lactose, and xylose.

Publications

Regulation of metabolism in Escherichia coli during growth on mixtures of the non-glucose sugars: arabinose, lactose, and xylose.

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