Thin agar film for enhanced fungal growth and microscopic viewing in a new sealable fungal culture case

Abstract

This project was undertaken to find ways to enhance fungus colony maturation, to make viewing of fungal cultures easier, and to reduce disruption of the fungal structures to be observed for identification. Accordingly, a technique using a thin (0.2-mm) agar film that avoids problems inherent in traditional methods of fungal culture and identification was developed. In addition, to accommodate the 0.2-mm layer of agar film and a contiguous thicker 4-mm section of agar, a sealable fungal culture case that fits within microscope stage calipers and under the objective lenses was invented. The growth and identification of 28 organisms were evaluated in the sealable fungal culture cases and on double-pour agar plates by using potato dextrose agar in both. Compared with results obtained with the double-pour agar plates (rated as 'good'), fungal growth and identification with the sealable fungal culture case were superior (rated as 'excellent') (P < 0.05, chi-square test). The thin agar film limits excessive mycelial growth, while it often promotes complete sporulation or other forms of maturation of the fungal colony. More importantly, the thin agar film allows direct microscopic viewing of the developing fungal colonies. The portion of the sealable fungal culture case with the 4-mm layer of agar can be used for evaluation of colony pigment and texture. In conclusion, this new sealable fungal culture case allows direct viewing and earlier fungal species identification with greater intrinsic safety.