Dataset Information

Analysis of the mechanism and regulation of lactose transport and metabolism in Clostridium acetobutylicum ATCC 824.

ABSTRACT: Although the acetone-butanol-ethanol fermentation of Clostridium acetobutylicum is currently uneconomic, the ability of the bacterium to metabolize a wide range of carbohydrates offers the potential for revival based on the use of cheap, low-grade substrates. We have investigated the uptake and metabolism of lactose, the major sugar in industrial whey waste, by C. acetobutylicum ATCC 824. Lactose is taken up via a phosphoenolpyruvate-dependent phosphotransferase system (PTS) comprising both soluble and membrane-associated components, and the resulting phosphorylated derivative is hydrolyzed by a phospho-beta-galactosidase. These activities are induced during growth on lactose but are absent in glucose-grown cells. Analysis of the C. acetobutylicum genome sequence identified a gene system, lacRFEG, encoding a transcriptional regulator of the DeoR family, IIA and IICB components of a lactose PTS, and phospho-beta-galactosidase. During growth in medium containing both glucose and lactose, C. acetobutylicum exhibited a classical diauxic growth, and the lac operon was not expressed until glucose was exhausted from the medium. The presence upstream of lacR of a potential catabolite responsive element (cre) encompassing the transcriptional start site is indicative of the mechanism of carbon catabolite repression characteristic of low-GC gram-positive bacteria. A pathway for the uptake and metabolism of lactose by this industrially important organism is proposed.

SUBMITTER: Yu Y

PROVIDER: S-EPMC1828815 | biostudies-literature | 2007 Mar

REPOSITORIES: biostudies-literature

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Publications

Analysis of the mechanism and regulation of lactose transport and metabolism in Clostridium acetobutylicum ATCC 824.

Yu Yang Y Tangney Martin M Aass Hans C HC Mitchell Wilfrid J WJ

Applied and environmental microbiology 20070105 6

Although the acetone-butanol-ethanol fermentation of Clostridium acetobutylicum is currently uneconomic, the ability of the bacterium to metabolize a wide range of carbohydrates offers the potential for revival based on the use of cheap, low-grade substrates. We have investigated the uptake and metabolism of lactose, the major sugar in industrial whey waste, by C. acetobutylicum ATCC 824. Lactose is taken up via a phosphoenolpyruvate-dependent phosphotransferase system (PTS) comprising both solu ...[more]

PMID: 17209069

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Project description:Bacterial fermentation of carbohydrates from sustainable lignocellulosic biomass into commodity chemicals by the anaerobic bacterium Clostridium acetobutylicum is a promising alternative source to fossil fuel-derived chemicals. Recently, it was demonstrated that xylose is not appreciably fermented in the presence of arabinose, revealing a hierarchy of pentose utilization in this organism (L. Aristilde, I. A. Lewis, J. O. Park, and J. D. Rabinowitz, Appl Environ Microbiol 81:1452-1462, 2015, https://doi.org/10.1128/AEM.03199-14). The goal of the current study is to characterize the transcriptional regulation that occurs and perhaps drives this pentose hierarchy. Carbohydrate consumption rates showed that arabinose, like glucose, actively represses xylose utilization in cultures fermenting xylose. Further, arabinose addition to xylose cultures led to increased acetate-to-butyrate ratios, which indicated a transition of pentose catabolism from the pentose phosphate pathway to the phosphoketolase pathway. Transcriptome sequencing (RNA-Seq) confirmed that arabinose addition to cells actively growing on xylose resulted in increased phosphoketolase (CA_C1343) mRNA levels, providing additional evidence that arabinose induces this metabolic switch. A significant overlap in differentially regulated genes after addition of arabinose or glucose suggested a common regulation mechanism. A putative open reading frame (ORF) encoding a potential catabolite repression phosphocarrier histidine protein (Crh) was identified that likely participates in the observed transcriptional regulation. These results substantiate the claim that arabinose is utilized preferentially over xylose in C. acetobutylicum and suggest that arabinose can activate carbon catabolite repression via Crh. Furthermore, they provide valuable insights into potential mechanisms for altering pentose utilization to modulate fermentation products for chemical production. IMPORTANCE Clostridium acetobutylicum can ferment a wide variety of carbohydrates to the commodity chemicals acetone, butanol, and ethanol. Recent advances in genetic engineering have expanded the chemical production repertoire of C. acetobutylicum using synthetic biology. Due to its natural properties and genetic engineering potential, this organism is a promising candidate for converting biomass-derived feedstocks containing carbohydrate mixtures to commodity chemicals via natural or engineered pathways. Understanding how this organism regulates its metabolism during growth on carbohydrate mixtures is imperative to enable control of synthetic gene circuits in order to optimize chemical production. The work presented here unveils a novel mechanism via transcriptional regulation by a predicted Crh that controls the hierarchy of carbohydrate utilization and is essential for guiding robust genetic engineering strategies for chemical production.

Dataset Information

Analysis of the mechanism and regulation of lactose transport and metabolism in Clostridium acetobutylicum ATCC 824.

Publications

Analysis of the mechanism and regulation of lactose transport and metabolism in Clostridium acetobutylicum ATCC 824.

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