Isolation and modulation of growth of a colonization-impaired strain of Enterobacter cloacae in cucumber spermosphere

Abstract

Enterobacter cloacae A-46 was isolated for use in an environmental containment strategy for genetically modified derivative strains with enhanced biocontrol activity. The population of E. cloacae A-46, a transposon mutant of the plant-beneficial bacterium E. cloacae 501R3, increased 10-fold (significant increase at P < or = 0.05) in cucumber spermosphere when applied to cucumber seeds along with casamino acids. In contrast, strain A-46 was incapable of proliferation in cucumber spermosphere in the absence of casamino acids. Populations of strain A-46 also failed to increase in corn, cowpea, sunflower, and wheat spermospheres in the absence of casamino acids, while populations of strain 501R3 increased 3162-, 512-, 1698-, and 93-fold, respectively. In addition, the persistence of strain A-46 in corn, cucumber, and sunflower rhizospheres and in natural soil was greatly reduced compared with the parental strain 501R3.