18 - Arxiozyma van der Walt & Yarrow

Abstract

This chapter focuses on Arxiozyma genus and its constituent species. Asexual reproduction in this genus is by multilateral budding on a narrow base and its cells are spheroidal, ovoidal, or occasionally elongate. True hyphae are not produced, but pseudohyphae may form. Pellicles are not formed on the surface of liquid media and Asci are unconjugated, persistent, and produce one or rarely two spheroidal ascospores. Ascospores are verrucose to tuberculate. The only constituent species of this genus is Arxiozyma telluris. After 3 days at 25° C in 5% malt extract agar, the cells of this species appear as spheroidal, ellipsoidal, or infrequently elongate as single, or in pairs, or in small clusters. The growth is butyrous, dull-glistening, and tannish-white. After 7 days at 25° C in dalmau plate culture on morphology agar, growth under the coverglass shows no true hyphae, however pseudohyphae may be formed by some strains. Aerobic growth is white to tannish-white, faintly glistening, and butyrous. Single colonies are low convex with a depressed center and a pleasant, faintly acidic odor is present. Asci are transformed from unconjugated vegetative cells and produce one or infrequently two spheroidal ascospores. Transmission electron microscopy shows that ascospore surfaces are roughened by protuberances that arise from the outer layer of the spore wall.