Survival of Pseudomonas putida KT2440 in soil and in the rhizosphere of plants under greenhouse and environmental conditions

Pseudomonas putida KT2440 is a root colonizer of potential interest for the rhizoremediation of pollutants and the biological control of pests. The short- and long-term survival of this strain, as well as the possible effects of its introduction on different populations of indigenous soil bacteria, were tested in soil under greenhouse and field conditions. The greenhouse studies showed that inoculated P. putida KT2440 was able to establish itself after 3 d in nonvegetated soils at a density of 8±2×10 3 CFU g −1 soil. The introduction of this strain had no significant effect on the number of several soil bacteria including those that were resistant to tetracycline; those that utilized p-hydroxyphenylacetic acid as the sole C-source, and total fluorescent pseudomonads. In four independent field assays in nonplanted soils, the numbers of P. putida KT2440 decreased during 50 d from an initial density of 1×10 6 CFU g −1 soil to approximately 2±1×10 2 CFU g −1 soil. Thereafter, the number of cells was below detection limits (i.e.