The Ubiquinone System as a Taxonomic Aid in Aspergillus and its Teleomorphs

Summary

Ubiquinones (Q) are important carriers in the electron transport chain of respiratory systems. It has been shown that the number of isoprene units of the ubiquinone side chain is an excellent aid in identification of genera or subgeneric taxa in microbial taxonomy.

In Aspergillus, 9 or 10 isoprene units (Q-9 and Q-10) occur, together with a hydrogenated form Q-10(H2). We have studied the ubiquinone systems in Aspergillus in relation to the taxonomy of Raper and Fennell, who subdivided Aspergillus into species without metulae, species with or without metulae and species with metulae. In species without metulae, Q-9 occurs in sects Aspergillus and Restricti and most species in sect. Cervini; and Q-10 in sects Fumigati and Clavati. Subgen. Ornati was heterogeneous in ubiquinone systems, in agreement with the observations of morphological heterogeneity. In the sections which may or may not produce metulae, belonging to sects Nigri and Cremei possessed Q-9 ubiquinone, as did A. wentii. Nearly all species in sects Wentii, Flavi, Circumdati, Candidi and Sparsi possessed the Q-10(H2) system. Species in sects Nidulantes, Versicolores, Usti, Terrei and Flavipedes, which include species always producing metulae, all possessed Q-10(H2) ubiquinone without exception.

Xerophilic species had Q-9 or Q-10, while nearly all species having Hülle cells possessed only the Q-10(H2) system. The isoprene units of ubiquinone were highly correlated with morphological and physiological characters in the infrageneric taxa of Aspergillus.

This paper constitutes Part III of a series entitled “Ubiquinone systems in fungi”