Asexual Sporulation and Mycelial Growth in Axenic Cultures of Smittium Spp. (Trichomycetes)

SUMMARY

Four Smittium species were utilized in this study: S. culisetae, S. culicis, S. mucronatitm, and S. simulii, with an emphasis on the first three. Twelve carbon sources were tested for their effect on sporulation. Tryptone-glucose-vitamin medium (TGv) was the best complete medium for sporulation in S. culisetae at 22 C, and for S. culicis and S. mucronatum at 14 C. Maximum sporulation is much greater in S. culisetae than in the other two species. Deletion of glucose from the basic TGv medium enhanced sporulation but depressed growth, whereas addition of 1% glucose produced maximum growth but sporulation was reduced by about 60%. Full strength Brain-heart infusion medium (BHI) inhibited sporulation in the three species, but all produced maximum sporulation when the medium was diluted to 20% of the recommended strength. All three species grew well at 14 and 24 C, but only S. culisetae produced good growth at 30 C and was capable if some growth and sporulation at 34 C. B-sitosterol and sitosterol acetate (20 mg/liter of medium) were found to more than double spore production in S. mucronatum, but several other sterols reduced the number of spores. Mechanical shaking and aeration enhanced sporulation in S. culisetae. Whereas reduced aeration only slightly reduced mycelial growth, sporulation was greatly inhibited.