Submitted to: International Plant Growth Promoting Rhizobacteria Workshop
Publication Type: Abstract Only
Publication Acceptance Date: 5/30/2006
Publication Date: 5/30/2006
Citation: Roberts, D.P., Mckenna, L.F., Lohrke, S.M., Buyer, J.S., Liu, S., Hu, X., De Souza, J.T. 2006. Influence of catabolic capabilities of enterobacter cloacae on colonization of cucumber rhizosphere by this bacterium [abstract]. International Plant Growth Promoting Rhizobacteria Workshop. Interpretive Summary:
Technical Abstract: A library of mini-Tn5 Km transposon mutants of E. cloacae 501R3 was constructed to study the role of the bacterial genes and catabolic pathways, and the nutrients supplied by the host plant, during colonization of cucumber roots by E. cloacae. This library was screened for the loss of growth on minimal media containing various compounds detected in cucumber root exudate. Mutants C8 and M83 were each slightly reduced in the ability to utilize reduced carbon compounds released from cucumber roots relative to strain 501R3. Mutants C8 and M83 did not grow on galactose and serine or alanine, respectively, and were not significantly affected in the ability to colonize cucumber roots relative to strain 501R3. Molecular characterization of mutants A-11, M2, and M43 indicated that the mini-Tn5 Km insertions were in pfkA, sdhA, and aceF respectively. These genes play key roles in carbohydrate catabolism (pfkA, aceF) and the tricarboxylic acid cycle (sdhA, aceF). Mutants A-11 and M2 had a decreased ability to grow on carbohydrates and a decreased ability to grow on amino acids and TCA cycle intermediates, respectively, relative to strain 501R3. Mutants A-11 and M2 were moderately, but significantly, decreased relative to 501R3 in cucumber root colonization. Mutant M43 was affected in the utilization of carbohydrates and in the utilization of amino acids and organic acids and had a decreased ability to grow on all compounds released from cucumber roots relative to strain 501R3 and all other mutants discussed above. Mutant M43 was undetectable after 42 days in cucumber rhizosphere and was significantly reduced in colonization of cucumber roots relative to strains 501R3, C8, M83, A-11, and M2. Therefore, diminished catabolic capabilities by E. cloacae lead to diminished colonization capabilities in the cucumber rhizosphere.