Title: Regulatory Exaptation of the Catabolite Repression Protein (Crp)¿cAMP System in Pseudomonas Putida
Citation: ENVIRONMENTAL MICROBIOLOGY vol. 13 no. 2 p. 324-339
Publication Year: 2011
JRC N°: JRC59429
ISSN: 1462-2912
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC59429
DOI: 10.1111/j.1462-2920.2010.0233.x
Type: Articles in periodicals and books
Abstract: The genome of the soil bacterium Pseudomonas putida KT2440 encodes singular orthologs of genes crp (encoding the catabolite repression protein, Crp) and cya (adenylate cyclase) of Escherichia coli. In order to examine the functionality of the corresponding products, the levels of cAMP formed by P. putida cells were monitored either chemically or with a Dictyostelium biosensor in vivo, turning out to be < 40 pmoles/ml i.e. extremely low. The cyaPP gene was transcribed in vivo but failed to complement the lack of maltose consumption of a cya mutant of E. coli, thereby indicating that cyaPP was poorly translated or rendered non-functional in the heterologous host. Yet, generation of cAMP by CyaPP could be verified by expressing the cyaPP gene in a hyper-sensitive E. coli strain. On the other hand, the crpPP gene restored the metabolic capacities of an equivalent crp mutant of E. coli, but not in a double crp/cya strain, suggesting that the ability to regulate such functions required cAMP. In order to clarify the breadth of the Crp/cAMP system in P. putida, crp and cya mutants were generated and passed through a battery of phenotypic tests for recognition of gross metabolic properties and stress-endurance abilities. These assays revealed that the loss of each gene led in most (but not all) cases to the same phenotypic behavior, indicating a concerted functionality. Unexpectedly, none of the mutations affected the panel of C-compounds that can be used by P. putida as growth substrates, the mutants being impaired only in the use of various di-peptides as N sources. Furthermore, the lack of crp or cya had little influence on the gross growth fingerprinting of the cells. The poor physiological profile of the Crp-cAMP system of P. putida when compared with E. coli exposes a case of regulatory exaptation i.e. the process through which a property evolved for a particular function is co-opted for a new use.
JRC Directorate:Health, Consumers and Reference Materials

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