Growth, sporulation and pH tolerance of Furculomyces boomerangus and Austrosmittium biforme in axenic culture

Growth, sporulation, and pH tolerance of the insect gut fungi, Furculomyces boomerangus and Austrosmittium biforme (Trichomycetes, Harpellales, Legeri omycetaceae), were studied in axenic culture. Biomass and trichospore produ ction were considerably higher in shaken cultures after eight days than in stationary flasks. In stationary cultures, the pH of the filtrates remained acidic, but shaken cultures became alkaline during growth. Biomass varied at different pH values. Furculomyces boomerangus grew best at pH 5.0, while Austrosmittium biforme did so at pH 6.5. Both endobionts produced minimum biomass at pH 4.0. Higher numbers of viable trichospores were produced in s haken cultures than in stationary cultures. Total trichospore production wa s highest between pH 6.5 and 8.0, but viable trichospores were most abundan t at pH 8.5. No viable trichospores were recorded at pH 4.0. The study indi cates that both F: boomerangus and A. biforme are pH tolerant and can grow under different cultural regimes in vitro.