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Adenosine 3':5'-cyclic monophosphate and catabolite repression in Escherichia coli.

ABSTRACT: 1. Both permanent and transient catabolite repression of beta-galactosidase synthesis in Escherichia coli are abolished by 5mm-3':5'-cyclic-AMP when elicited by glucose, but not when caused by a mixture of glucose, glucose 6-phosphate, gluconate and casein hydrolysate (casamino acids). 2. Glucose uptake is slightly increased by 3':5'-cyclic-AMP. 3. No significant effects of the nucleotide were found on the synthesis of protein and RNA, either in exponential growth on one substrate, or during a growth shift from glycerol to glycerol plus glucose. 4. Marked changes in the soluble-protein profiles of cells growing in glycerol and glucose were caused by the presence of 3':5'-cyclic-AMP. 5. Measurements of (14)CO(2) release from specifically-labelled glucose showed that 3':5'-cyclic-AMP greatly stimulated glycolytic activity while having a minor depressing effect on the metabolic flow through the pentose phosphate cycle. 6. The concentrations of several metabolic intermediates, particularly fructose 1,6-diphosphate, were greatly affected by the presence of 3':5'-cyclic-AMP. 7. Several metabolites partially relieved glucose repression of beta-galactosidase synthesis in EDTA-treated cells; three out of five of these metabolites reversed the effect more effectively than did 3':5'-cyclic-AMP. 8. The evidence for and against a direct role for 3':5'-cyclic-AMP is discussed. It is concluded that the evidence for indirect action is at least as strong as that for direct action.

SUBMITTER: Moses V

PROVIDER: S-EPMC1179216 | biostudies-other | 1970 Jul

REPOSITORIES: biostudies-other

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Project description:1. Repression by glucose of beta-galactosidase synthesis is spontaneously reversible in all strains of Escherichia coli examined long before the glucose has all been consumed. The extent of recovery and the time necessary for reversal differ among various strains. Other inducible enzymes show similar effects. 2. This transient effect of glucose repression is observed in constitutive (i(-)) and permease-less (y(-)) cells as well as in the corresponding i(+) and y(+) strains. 3. Repression is exerted by several rapidly metabolizable substrates (galactose, ribose and ribonucleosides) but not by non-metabolized or poorly metabolized compounds (2-deoxyglucose, 2-deoxyribose, phenyl thio-beta-galactoside and 2-deoxyribonucleosides). 4. The transient repression with glucose is observed in inducible cells supplied with a powerful inducer of beta-galactosidase synthesis (e.g. isopropyl thio-beta-galactoside) but not with a weak inducer (lactose); in the latter instance glucose repression is permanent. Diauxic growth on glucose plus lactose can be abolished by including isopropyl thio-beta-galactoside in the medium. 5. In some strains phosphate starvation increases catabolite repression; in others it relieves it. Adenine starvation in an adenine-requiring mutant also relieves catabolite repression by glycerol but not that by glucose. Restoration of phosphate or adenine to cells starved of these nutrients causes a pronounced temporary repression. Alkaline-phosphatase synthesis is not affected by the availability of adenine. 6. During periods of transient repression of induced enzyme synthesis the differential rate of RNA synthesis, measured by labelled uracil incorporation in 2min. pulses, shows a temporary rise. 7. The differential rate of uracil incorporation into RNA falls during exponential growth of batch cultures of E. coli. This is equally true for uracil-requiring and non-requiring strains. The fall in the rate of incorporation has been shown to be due to a real fall in the rate of RNA synthesis. The significance of the changes in the rate of RNA synthesis is discussed. 8. A partial model of catabolite repression is presented with suggestions for determining the chemical identification of the catabolite co-repressor itself.

Project description:The extracellular matrix protects Escherichia coli from immune cells, oxidative stress, predation, and other environmental stresses. Production of the E. coli extracellular matrix is regulated by transcription factors that are tuned to environmental conditions. The biofilm master regulator protein CsgD upregulates curli and cellulose, the two major polymers in the extracellular matrix of uropathogenic E. coli (UPEC) biofilms. We found that cyclic AMP (cAMP) regulates curli, cellulose, and UPEC biofilms through csgD The alarmone cAMP is produced by adenylate cyclase (CyaA), and deletion of cyaA resulted in reduced extracellular matrix production and biofilm formation. The catabolite repressor protein (CRP) positively regulated csgD transcription, leading to curli and cellulose production in the UPEC isolate, UTI89. Glucose, a known inhibitor of CyaA activity, blocked extracellular matrix formation when added to the growth medium. The mutant strains ΔcyaA and Δcrp did not produce rugose biofilms, pellicles, curli, cellulose, or CsgD. Three putative CRP binding sites were identified within the csgD-csgB intergenic region, and purified CRP could gel shift the csgD-csgB intergenic region. Additionally, we found that CRP binded upstream of kpsMT, which encodes machinery for K1 capsule production. Together our work shows that cAMP and CRP influence E. coli biofilms through transcriptional regulation of csgD IMPORTANCE The catabolite repressor protein (CRP)-cyclic AMP (cAMP) complex influences the transcription of ∼7% of genes on the Escherichia coli chromosome (D. Zheng, C. Constantinidou, J. L. Hobman, and S. D. Minchin, Nucleic Acids Res 32:5874-5893, 2004, https://dx.doi.org/10.1093/nar/gkh908). Glucose inhibits E. coli biofilm formation, and ΔcyaA and Δcrp mutants show impaired biofilm formation (D. W. Jackson, J.W. Simecka, and T. Romeo, J Bacteriol 184:3406-3410, 2002, https://dx.doi.org/10.1128/JB.184.12.3406-3410.2002). We determined that the cAMP-CRP complex regulates curli and cellulose production and the formation of rugose and pellicle biofilms through csgD Additionally, we propose that cAMP may work as a signaling compound for uropathogenic E. coli (UPEC) to transition from the bladder lumen to inside epithelial cells for intracellular bacterial community formation through K1 capsule regulation.

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Adenosine 3':5'-cyclic monophosphate and catabolite repression in Escherichia coli.

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