Factors Affecting Multiplication, Survival and Death of a Bacterium (γ-HCH-decomposing Sphingomonas paucimobilis SS86) Inoculated to Soil: Previous Growth Condition, Competition and Predation

The significance of several factors (pre-culture conditions, competition, and predation) affecting the population dynamics of γ-HCH-decomposing bacterium, Sphingomonas paucimobilis SS86 inoculated to soil was examined. The exponentially-growing cells of SS86 inoculated to soil declined quickly immediately after inoculation. This might be caused by physiological inadaptation of the bacterial cells to the oligotrophic soil environment. Cell of the SS86 pre-cultured and harvested at late-stationary phase showed better survival than growing cells. Competition between the inoculated SS86 and indigenous soil microorganisms for the natural substrate restricted the multiplication of SS86 in γ-HCH-free soil, but its effect on the decline was relatively small. The predominant factor causing the decline of SS86 in soil was considered to be the grazing activity of protozoa.