Mycocin production in Trichosporon pullulans populations colonizing tree exudates in the spring.

Mycocin production was demonstrated in Trichosporon pullulans, which is a dominant member of the yeast community in tree exudates released in the early spring (spring sap). Mycocin synthesis was associated with dsRNA-containing virus-like particles. Natural strains of Tr. pullulans free of dsRNA have a sensitive phenotype, and a mycocinogenic strain cured of small dsRNA becomes sensitive to its own mycocin. The mycocin studied was active against isolates from tree exudations only but not against Tr. pullulans strains isolated from other habitats. No activity was found against any other yeast species. The competitive advantage of mycocin production at the population level was exemplified by the predominance of mycocinogenic strains both in laboratory model communities and in natural populations.