Induction of pigmentation ofThielaviopsis basicolaand other fungi by a bacterium isolated from soil

摘要

A blue-pigmented bacterium was isolated from soil and as a contaminant in cultures ofThielaviopsis basicolaisolated from diseased tobacco roots. When the bacterium, a species ofPseudomonas, was grown in culture in association withT. basicola, a blue pigmentation was observed in the fungus. In addition to pigmentation of hyphae and conidia, other deleterious effects were induced in the fungus, including cytoplasmic granulation, vacuolation, contraction of cellular contents, reduced growth, and subsequent death of the affected cells. Other fungi, includingFusarium oxysporumf. sp.lycopersici, Botrytis convoluta, Rhizopussp., andMucorsp., were similarly affected. Hyphal pigmentation and other effects were observed only when viable bacteria were growing in intimate contact with the fungus mycelium. The pigment-inducing substance was not secreted into the culture media and was not obtained from lysed bacteria. Pigmentation and the other characteristic effects onT. basicolawere not observed when the fungus and bacteria were added to soil. Similarly no significant reduction in severity of black root rot of tobacco seedlings was obtained when the blue bacteria were added toT. basicolainfested soil.