Studies on the Morphology, Physiology and Taxonomy of the 'Kerosene Fungus' Amorphotheca Resinae Parbery, (Conidial State; Cladosporium Resinae (Lindau) De Vries

Abstract

Isolates of the 'kerosene fungus' from 'New Zealand soil, air, and aviation and lighting kerosene were studied and the four asexual forms described in the literature were found. Two of these are morphologically distinct; forma avellaneum, which was the only form isolated from nature, and forma resinae which occurred as a saltant in cultures of forma avellaneum. Intermediates between the two forms and variants of forma avellaneum occurred. The other two forms and forma albidum, an albino which was morphologically similar to forma avellaneum, and forma sterile which did not produce any reproductive structures. All were relatively stable except forma sterile. The different forms are described. The fine structure of spores of the 'kerosene fungus' was studied for the first time in the transmission and scanning electron microscope. Spores were found to be uninucleate and possessed an unusually thick wall made up of an outer thin and inner thicker layer. The enclosed 'membrane' was also unusually thick and convoluted. Some conidiophores and ramoconidia were warted but blastospores of all forms lacked surface ornamentation. Two types of ascocarp were found under different cultural conditions; the presence of the funnel-shaped appendage on the pitcher-shaped ascocarp and amorphous peridium in this fungus is unique. Xylose and ammonium chloride were found to be the best carbon and nitrogen sources respectively. The optimum temperature for growth was around 30°C on solid media but close to 25°C in liquid media. The optimum pH is around 3. Pigment production was greatest at higher pH values. Exogenous nutrients are required for germination. The germ-tube wall is the continuation of the inner spore wall. Near u/v irradiation depressed growth: natural light decreased sporulation in forma avellaneum but promoted sporulation in forma albidum. On the basis of the present study and in the light of published work, it is concluded that the asexual state of the 'kerosene fungus' is correctly placed in the genus Cladosporium. The subspecific epithets should be retained as an aid to recognization, but probably have no taxonomic significance. A study of the sexual state indicates relationships with the Eurotiales but this fungus cannot be accommodated in any of the existing families. The new family, Amorphothecaceae, erected by Parbery (1969) and the name Amorphotheca resinae is accepted.