Affiliation:
1. Department of Applied Microbiology, Yeungnam University, Gyongsan 713-749, Korea
Abstract
An actively antagonistic bacterium that could be used as a biocontrol agent against
Fusarium solani
, which causes root rots with considerable losses in many important crops, was isolated from a ginseng rhizosphere and identified as a strain of
Pseudomonas stutzeri
. In several biochemical tests with culture filtrates of
P. stutzeri
YPL-1 and in mutational analyses of antifungal activities of reinforced or defective mutants, we found that the anti-
F. solani
mechanism of the bacterium may involve a lytic enzyme rather than a toxic substance or antibiotic.
P. stutzeri
YPL-1 produced extracellular chitinase and laminarinase when grown on different polymers such as chitin, laminarin, or
F. solani
mycelium. These lytic extracellular enzymes markedly inhibited mycelial growth rather than spore germination and also caused lysis of
F. solani
mycelia and germ tubes. Scanning electron microscopy revealed degradation of the
F. solani
mycelium. Abnormal hyphal swelling and retreating were caused by the lysing agents from
P. stutzeri
YPL-1, and a penetration hole was formed on the hyphae in the region of interaction with the bacterium; the walls of this region were rapidly lysed, causing leakage of protoplasm. Genetically bred
P. stutzeri
YPL-1 was obtained by transformation of the bacterium with a broad-host-range vector, pKT230. Also, the best conditions for the transformation were investigated.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
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