ABSTRACT
Black Aspergilli (Aspergillus niger species group, Raper and Fennell, 1965; Aspergillus section Nigri, Gams et al., 1985) have a significant impact on modern society. Many species belonging to this group cause food spoilage, and several of them are used in the fermentation industry to produce different hydrolytic enzymes such as amylases or lipases, and organic acids like citric acid and gluconic acid (for references, see Raper and Fennell, 1965; Smith and Pateman, 1977; Bennett and Klich, 1992; Kozakiewicz, 1989). They are also candidates for genetic manipulation in the biotechnological industries since A. niger has been granted the GRAS (generally regarded as safe) status by the Food and Drug Administration of the US government. Black Aspergilli have long had one of the better taxonomic descriptions among the fungi. Mosseray (1934; cf. Raper and Fennell,
MATERIALS AND METHODS
RESULTS
GENOTYPIC APPROACHES
generated ribosomal DNA (rDNA) patterns. The two groups were also clearly distinguishable by their hybridization patterns when pectin lyase genes (pelA, pelB) and the pyruvate kinase (pki) gene were used as probes in DNA hybridization experiments. The two groups found were proposed to represent different species, namely A. niger and A. tubingensis. Examination of other species not belonging to the A. niger aggregate was also carried out. A. foetidus strains, classified into a different species by Al-Musallam (1980), showed the same nuclear DNA RFLPs as A. niger. A. helicothrix was found to represent only a morphological variant of A. ellipticus, and A. aculeatus should only be ranked to subspecies status as it showed the same Smal-digested rDNA pattern as the A. japonicus strains examined.
