Cuticular disruption and mortality of Caenorhabditis elegans exposed to culture filtrate of Byssochlamys nivea Westling

A strain of a Byssochlamys nivea, isolated from saline mud in Western Austr alia as a part of statewide survey of soil fungi for nematophagous activity , was evaluated for its effect on nematodes. Culture filtrate of the fungus grown on potato dextrose broth for 7 days caused structural changes in the cuticle, aggregation of individuals, and mortality of Caenorhabditis elega ns. In addition, the culture filtrate completely inhibited hatching of C. e legans eggs. Exudates from agar colonies also caused cuticular disruption a nd mortality of C. elegans. The cuticular disruption observed, not reported in nematodes before, was initiated in the labial region and spread towards the posterior region of the nematode within 10 min of application. This re action occurred only in live nematodes. Cuticular disruption and mortality caused by the culture filtrate varied according to growth conditions. The a ctive compound(s) in the culture filtrate were thermostable (100 degreesC f or 1 h); however freezing the culture filtrate (-20 degreesC for 2 days) el iminated the activities, as did dialysis (< 14 000 molecular weight). Cutic ular disruption and mortality were also observed when the nematode was expo sed to culture filtrates of two other strains of B. nivea supplied by CBS, The Netherlands. The culture filtrate also inhibited in vitro growth of the plant-pathogenic fungi Fusarium oxysporum, Gaeumannomyces graminis var. tr itici, Phytophthora cinnamomi, Pythium irregulare and Rhizoctonia solani.