ISOLATION AND MODULATION OF GROWTH OF A COLONIZATION-IMPAIRED STRAIN OF ENTEROBACTER-CLOACAE IN CUCUMBER SPERMOSPHERE

Enterobacter cloacae A-46 was isolated for use in an environmental con tainment strategy for genetically modified derivative strains with enh anced biocontrol activity. The population of E. cloacae A-46, a transp oson mutant of the plant beneficial bacterium E. cloacae 501R3, increa sed 10-fold (significant increase at P less than or equal to 0.05) in cucumber spermosphere when applied to cucumber seeds along with casami no acids. In contrast, strain A-46 was incapable of proliferation in c ucumber spermosphere in the absence of casamino acids. Populations of strain A-46 also failed to increase in corn, cowpea, sunflower, and wh eat spermospheres in the absence of casamino acids, while populations of strain 501R3 increased 3162-, 512-, 1698-, and 93-fold, respectivel y. In addition, the persistence of strain A-46 in corn, cucumber, and sunflower rhizospheres and in natural soil was greatly reduced compare d with the parental strain 501R3.