INHIBITORY-ACTION OF ELEMENTAL SULFUR (S-DEGREES) ON FUNGAL SPORES

The fungitoxic effect of increasing concentrations of elemental sulphu r (S-degrees) was studied during the pregermination period of spores o f Phomopsis viticola and conidia of Neurospora crassa. High concentrat ions of S-degrees (> 10 muM final concentration) inhibited respiratory activities strongly and decreased the ATP content of spores and conid ia. S-degrees at low concentrations (1 and 3 AM final concentration) d id not inhibit the respiratory activities or ATP content of spores and conidia. In spores of P. viticola, low concentrations of S-degrees we re reduced by the cells with the production of hydrogen sulphide (H2S) , principally at the level of the respiratory chain. However, in the p resence of a high concentration of S-degrees, the capacity to reduce S -degrees increased, and was then most probably independent of the resp iratory activities. Proteic and nonproteic sulphydryl groups important in cellular metabolism were probably responsible for almost all the r eduction of S-degrees. In fact, the addition of increasing concentrati ons of S-degrees to spores of P. viticola resulted in a dramatic incre ase in oxidized glutathione, suggesting the participation of reduced g lutathione in S-degrees reduction. In conclusion, we suggest that the fungicidal action of S-degrees is probably related to the oxidation of important sulphydryl groups and not to the competitive interaction be tween S-degrees and oxygen at the level of the respiratory chain.