Submitted to: International Plant Growth Promoting Rhizobacteria Workshop
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 2000
Publication Date: N/A
Technical Abstract: Enterobacter cloacae A-11 is a prototrophic glycolytic mutant of strain 501R3 with a single mini Tn5-Km transposon insertion in pfkA. We extend our analysis of strain A-11 here to include the importance of pfkA and glycolysis in suppression of damping-off of cucumber caused by Pythium ultimum and colonization of cucumber roots in natural soil. Seed treatments containing strains 501R3 and A-11 both provided similar and significant levels of suppression of damping-off of cucumber caused by P. ultimum when applied as seed treatments in biological control experiments performed in potting mix. Oxygen consumption experiments were performed with carbohydrates and amino acids detected in cucumber seed exudates as the sole source of reduced carbon using oxygen microelectrodes. Strain A-11 had significantly lower oxygen consumption than strain 501R3 on galactose, glucose, maltose, mannitol, mannose, raffinose, and trehalose. Three of these cabohydrates, glucose, mannitol, and raffinose are prominen in cucumber exudates. Data from these studies are consistent with the hypothesis that the total carbohydrate catabolic capabilities of E. cloacae are not required for suppression of damping-off of cucumber caused by P. ultimum. In contrast, strain A-11 was reduced relative to strain 501R3 on cucumber roots at 16 days and 43 days in natural soil. It is possible that the inability to metabolize specific carbohydrates impacts long-term persistence of E. cloacae on cucumber roots.