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

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.

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Catabolite Repression Control by Crc in 2xYT Medium Is Mediated by Posttranscriptional Regulation of bkdR Expression in Pseudomonas putida

Journal of Bacteriology ◽

10.1128/jb.182.4.1150-1153.2000 ◽

2000 ◽

Vol 182 (4) ◽

pp. 1150-1153 ◽

Cited By ~ 45

Author(s):

Kathryn L. Hester ◽

K. T. Madhusudhan ◽

John R. Sokatch

Keyword(s):

Pseudomonas Putida ◽

Catabolite Repression ◽

Posttranscriptional Regulation ◽

Keto Acid ◽

Wild Type ◽

Transcript Levels ◽

Acid Dehydrogenase ◽

Rich Media ◽

Branched Chain ◽

Control Protein

ABSTRACT The effect of growth in 2xYT medium on catabolite repression control in Pseudomonas putida has been investigated using the bkd operon, encoding branched-chain keto acid dehydrogenase. Crc (catabolite repression control protein) was shown to be responsible for repression of bkd operon transcription in 2xYT. BkdR levels were elevated in a P. putida crcmutant, but bkdR transcript levels were the same in both wild type and crc mutant. This suggests that the mechanism of catabolite repression control in rich media by Crc involves posttranscriptional regulation of the bkdR message.

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Simultaneous Catabolite Repression between Glucose and Toluene Metabolism in Pseudomonas putida Is Channeled through Different Signaling Pathways

Journal of Bacteriology ◽

10.1128/jb.00679-07 ◽

2007 ◽

Vol 189 (18) ◽

pp. 6602-6610 ◽

Cited By ~ 75

Author(s):

Teresa del Castillo ◽

Juan L. Ramos

Keyword(s):

Glucose Metabolism ◽

Pseudomonas Putida ◽

Catabolite Repression ◽

Carbon Sources ◽

Flux Analysis ◽

Glucose Determination ◽

Net Flux ◽

Glucose 6 Phosphate Dehydrogenase ◽

Metabolism Gene

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.

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