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The Crc/CrcZ-CrcY global regulatory system helps integrating gluconeogenic and glycolytic metabolism in Pseudomonas putida

ABSTRACT: In metabolically versatile bacteria, carbon catabolite repression (CCR) facilitates the preferential assimilation of the most efficient carbon sources, improving growth rate and fitness. In Pseudomonas putida, the Crc protein and the CrcZ and CrcY small RNAs (sRNAs), which are believed to antagonise Crc, are key players in CCR. Contrary to what occurs in other bacterial species, succinate or glucose elicit a weak CCR in this bacterium. We combined metabolic, transcriptomics and constraints-based metabolic flux analyses to clarify whether P. putida prefers succinate or glucose, and the role of the Crc/CrcZ-CrcY regulatory system in their metabolization. Succinate was consumed faster than glucose and allowed a higher growth rate. However, both compounds were co-metabolised when provided simultaneously. The levels of CrcZ and CrcY were lower when both substrates were present than when only one of them was provided, suggesting a role for Crc in coordinating metabolism. Metabolic reconstructions suggested that, when both substrates are present, Crc works to organize a metabolism in which carbon compounds flow in two opposite directions: from glucose to pyruvate, and from succinate to pyruvate. Therefore, Crc serves not only to favour the assimilation of preferred compounds, but also to balance the carbon fluxes, optimising metabolism and growth.

ORGANISM(S): Pseudomonas putida KT2440

PROVIDER: GSE63987 | GEO | 2015/03/06

SECONDARY ACCESSION(S): PRJNA269721

REPOSITORIES: GEO

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Project description:Strains of Pseudomonas putida have emerged as promising biocatalysts for the conversion of sugars and aromatics obtained from lignocellulosic biomass. Understanding the role of carbon catabolite repression (CCR) in these strains is critical to optimizing the conversion of biomass to fuels and chemicals. The functioning of CCR in a P. putida strain, P. putida M2, capable of growing on both hexose and pentose sugars as well as aromatics, was investigated by cultivation experiments, proteomics, and CRISPRi-based gene repression. Strain M2 was able to co-utilize sugars and aromatics simultaneously; however, during co-cultivation with glucose and phenylpropanoid aromatics (p-coumarate and ferulate), intermediates (4-hydroxybenzoate and vanillate) accumulated, and substrate consumption was incomplete. In contrast, xylose-aromatic consumption resulted in transient intermediate accumulation and complete aromatic consumption, while xylose was incompletely consumed. Proteomics analysis of these co- cultivations revealed that glucose exerted stronger repression compared to xylose on the proteins involved in aromatic catabolism. Key glucose (Eda) and xylose (XylX) catabolic proteins were also identified at lower abundance during co-cultivation with aromatics implying simultaneous catabolite repression by sugars and aromatics. Downregulation of crc mediated by CRISPRi led to faster growth and uptake of both glucose and p-coumarate in the CRISPRi strains compared to the control while no difference was observed on xylose + p-coumarate. The increased abundance of the Eda protein and amino acids biosynthesis proteins in the CRISPRi strain further supported these observations. Lastly, small RNAs (sRNAs) sequencing results showed that the levels of CrcY and CrcZ homologs in M2, previously identified as sRNAs involved in CCR in P. putida strains, were lower under strong CCR (glucose + p-coumarate) condition compared to when repression was absent (p-coumarate or glucose only).

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The Crc/CrcZ-CrcY global regulatory system helps integrating gluconeogenic and glycolytic metabolism in Pseudomonas putida

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