Search

[Objectives] This paper aimed to study the nematicidal activity of the Pseudomonas protegens Pf-5, and to identify the major nematicidal compounds produced by this strain. [Methods] The unmarked deletion mutants of Pf-5 were constructed based on sucrose-induced(sacB gene)lethalality. The model nematodes Caenorhabditis elegans was used as the target. The strains were labeled with green fluorescent protein gene to study the lethal effect of the strain on this nematode. The possible action site of Pf-5 strain was observed by using scanning and transmission electron microscopy. [Results] The Pf-5 strain had strong lethal activity against C. elegans. The LCM of Pf-5 against C. elegans at 48 h and 96 h.was respectively 4.92xl07 CFU·mL-1 and 3.58xlO6 CFU·mL-1. When treated C. elegans with Pf-5 for 48 h, the lethal rate was 73.57%,but when Jit I) gene was knocked out, the lethal activity of PfSufUD was significantly reduced, only 25.04% compared to the wide type. When Delivery domain and CHOPS domain of July gene were respectively deleted, the lethal activity of mutants also significantly decreased. This indicated that the FiteD protein was the major nematicidal substance produced by Pf-5 strain. Scanning electron microscopy showed that Pf-5 strain and its mutant did not destroy the body wall of nematode. But when observed using transmission electron microscopy,the results had showed that the intestinal villi of nematode became thinner, and even fell off, but the mutant Pf-5μfiD didn't have such effect. [Conclusions] The nematicidal substance in the P. protegens Pf-5 strain is the FitD protein,and its site of action is the intestinal tract. [ABSTRACT FROM AUTHOR]