Faculty Opinions recommendation of Two small RNAs, CrcY and CrcZ, act in concert to sequester the Crc global regulator in Pseudomonas putida, modulating catabolite repression.

ABSTRACT Pseudomonas putida KT2440(pWW0) can use toluene via the TOL plasmid-encoded catabolic pathways and can use glucose via a series of three peripheral chromosome-encoded routes that convert glucose into 6-phosphogluconate (6PG), namely, the glucokinase pathway, in which glucose is transformed to 6PG through the action of glucokinase and glucose-6-phosphate dehydrogenase. Alternatively, glucose can be oxidized to gluconate, which can be phosphorylated by gluconokinase to 6PG or oxidized to 2-ketogluconate, which, in turn, is converted into 6PG. Our results show that KT2440 metabolizes glucose and toluene simultaneously, as revealed by net flux analysis of [13C]glucose. Determination of glucokinase and gluconokinase activities in glucose metabolism, gene expression assays using a fusion of the promoter of the Pu TOL upper pathway to ′lacZ, and global transcriptomic assays revealed simultaneous catabolite repression in the use of these two carbon sources. The effect of toluene on glucose metabolism was directed to the glucokinase branch and did not affect gluconate metabolism. Catabolite repression of the glucokinase pathway and the TOL pathway was triggered by two different catabolite repression systems. Expression from Pu was repressed mainly via PtsN in response to high levels of 2-dehydro-3-deoxygluconate-6-phosphate, whereas repression of the glucokinase pathway was channeled through Crc.

Download Full-text

The Target for the Pseudomonas putida Crc Global Regulator in the Benzoate Degradation Pathway Is the BenR Transcriptional Regulator

Journal of Bacteriology ◽

10.1128/jb.01604-07 ◽

2007 ◽

Vol 190 (5) ◽

pp. 1539-1545 ◽

Cited By ~ 63

Author(s):

Renata Moreno ◽

Fernando Rojo

Keyword(s):

Pseudomonas Putida ◽

Target Genes ◽

Carbon Sources ◽

Degradation Pathway ◽

Complete Medium ◽

Mrna Levels ◽

Global Regulator ◽

Benzoate Degradation ◽

Transcriptional Units ◽

Degradation Intermediates

ABSTRACT Crc protein is a global regulator involved in catabolite repression control of several pathways for the assimilation of carbon sources in pseudomonads when other preferred substrates are present. In Pseudomonas putida cells growing exponentially in a complete medium containing benzoate, Crc strongly inhibits the expression of the benzoate degradation genes. These genes are organized into several transcriptional units. We show that Crc directly inhibits the expression of the peripheral genes that transform benzoate into catechol (the ben genes) but that its effect on genes corresponding to further steps of the pathway (the cat and pca genes of the central catechol and β-ketoadipate pathways) is indirect, since these genes are not induced because the degradation intermediates, which act as inducers, are not produced. Crc inhibits the translation of target genes by binding to mRNA. The expression of the ben, cat, and pca genes requires the BenR, CatR, and PcaR transcriptional activators, respectively. Crc significantly reduced benABCD mRNA levels but did not affect those of benR. Crc bound to the 5′ end of benR mRNA but not to equivalent regions of catR and pcaR mRNAs. A translational fusion of the benR and lacZ genes was sensitive to Crc, but a transcriptional fusion was not. We propose that Crc acts by reducing the translation of benR mRNA, decreasing BenR levels below those required for the full expression of the benABCD genes. This strategy provides great metabolic flexibility, allowing the hierarchical assimilation of different structurally related compounds that share a common central pathway by selectively regulating the entry of each substrate into the central pathway.

Download Full-text

Expression of the Pseudomonas putida OCT Plasmid Alkane Degradation Pathway Is Modulated by Two Different Global Control Signals: Evidence from Continuous Cultures

Journal of Bacteriology ◽

10.1128/jb.185.16.4772-4778.2003 ◽

2003 ◽

Vol 185 (16) ◽

pp. 4772-4778 ◽

Cited By ~ 46

Author(s):

M. Alejandro Dinamarca ◽

Isabel Aranda-Olmedo ◽

Antonio Puyet ◽

Fernando Rojo

Keyword(s):

Carbon Source ◽

Pseudomonas Putida ◽

Catabolite Repression ◽

Degradation Pathway ◽

Independent Effect ◽

Physiological Status ◽

Carbon Limitation ◽

Alkane Degradation ◽

Global Control ◽

Ubiquinol Oxidase

ABSTRACT Expression of the genes of the alkane degradation pathway encoded in the Pseudomonas putida OCT plasmid are subject to negative and dominant global control depending on the carbon source used and on the physiological status of the cell. We investigated the signals responsible for this control in chemostat cultures under conditions of nutrient or oxygen limitation. Our results show that this global control is not related to the growth rate and responds to two different signals. One signal is the concentration of the carbon source that generates the repressing effect (true catabolite repression control). The second signal is influenced by the level of expression of the cytochome o ubiquinol oxidase, which in turn depends on factors such as oxygen availability or the carbon source used. Since under carbon limitation conditions the first signal is relieved but the second signal is not, we propose that modulation mediated by the cytochrome o ubiquinol oxidase is not classical catabolite repression control but rather a more general physiological control mechanism. The two signals have an additive, but independent, effect, inhibiting induction of the alkane degradation pathway.

Download Full-text

Crc Is Involved in Catabolite Repression Control of the bkd Operons of Pseudomonas putida andPseudomonas aeruginosa

Journal of Bacteriology ◽

10.1128/jb.182.4.1144-1149.2000 ◽

2000 ◽

Vol 182 (4) ◽

pp. 1144-1149 ◽

Cited By ~ 85

Author(s):

Kathryn L. Hester ◽

Jodi Lehman ◽

Fares Najar ◽

Lin Song ◽

Bruce A. Roe ◽

...

Keyword(s):

Pseudomonas Putida ◽

Catabolite Repression ◽

Carbon Sources ◽

Keto Acid ◽

Carbon Regulation ◽

Acid Dehydrogenase ◽

Transposon Mutants ◽

Branched Chain ◽

Glucose 6 Phosphate Dehydrogenase

ABSTRACT Crc (catabolite repression control) protein of Pseudomonas aeruginosa has shown to be involved in carbon regulation of several pathways. In this study, the role of Crc in catabolite repression control has been studied in Pseudomonas putida. The bkd operons of P. putida and P. aeruginosa encode the inducible multienzyme complex branched-chain keto acid dehydrogenase, which is regulated in both species by catabolite repression. We report here that this effect is mediated in both species by Crc. A 13-kb cloned DNA fragment containing the P. putida crc gene region was sequenced. Crc regulates the expression of branched-chain keto acid dehydrogenase, glucose-6-phosphate dehydrogenase, and amidase in both species but not urocanase, although the carbon sources responsible for catabolite repression in the two species differ. Transposon mutants affected in their expression of BkdR, the transcriptional activator of thebkd operon, were isolated and identified as crcand vacB (rnr) mutants. These mutants suggested that catabolite repression in pseudomonads might, in part, involve control of BkdR levels.

Download Full-text