Spore germination in Phycomyces blakesleeanus

Abstract

The spores of the Zygomycete Phycomyces blakesleeanus are usually exposed to heat or acetate to bring nearly all of them to germinate within hours. In the absence of such treatments, about 4% of the spores germinated each day after being inoculated in a filter-sterilized minimal medium that fully supports growth and differentiation. This rate remained constant for many days. The germination rate was higher in autoclave-sterilized minimal medium. We attribute this activation to the action of 5-hydroxymethylfurfural, a decomposition product of glucose heated under acidic conditions. Furfural had no effect. Gallic acid, accumulated and excreted by Phycomyces mycelia in considerable amounts, inhibited spore germination but not mycelial growth. The inhibition depended on the product of the gallic acid concentration and the exposure time and disappeared upon washing the spores. Gallic acid prevents spore germination in environments already colonized by Phycomyces.

Key Words:

• gallic acid
• 5-hydroxymethylfurfural
• Phycomyces blakesleeanus
• spontaneous spore germination