Pseudomonas stutzeri Strain Possessing a Self-Transmissible TOL-Like Plasmid Degrades Phenol and Promotes Maize Growth in Contaminated Environments

Abstract

Phenol is volatile organic pollutant that plants can little degrade. For complete degradation of volatile pollutants, we introduced Pseudomonas stutzeri strain P7 to phenol-contaminated soils. The strain effectively degraded phenol and even promoted plant growth. A TOL-like plasmid was detected in the strain and found to be responsible for phenol degradation and self-transmissible. In addition, phenol degradation by strain P7 was more rapid in the contaminated soils with than without plants over the full course of the experiment; especially by 5days, the phenol concentration was reduced by about 30% in soil without plants and reduced by about 50-65% in soil with plants. This situation also occurred when inoculated with different transconjugants. Furthermore, transfer frequencies of TOL-like plasmid were significantly higher in soil with than without plants. Populations of rifampin-resistant P7 strain remained relatively constant for 20days, while the number of rhizosphere bacteria that contained the degradative plasmids gradually increased at the later stages, suggesting that plants might stimulate plasmid transfer from strain P7 to indigenous bacteria, one possible reason for plant enhancing microbial degradation. This is attractive for implementation of combinations of phytoremediation and bioaugmentation in degradation of volatile pollutants that plants can little degrade.