Phylogeny, identification and nomenclature of the genus Aspergillus

Abstract

Aspergillus comprises a diverse group of species based on morphological, physiological and phylogenetic characters, which significantly impact biotechnology, food production, indoor environments and human health. Aspergillus was traditionally associated with nine teleomorph genera, but phylogenetic data suggest that together with genera such as Polypaecilum, Phialosimplex, Dichotomomyces and Cristaspora, Aspergillus forms a monophyletic clade closely related to Penicillium. Changes in the International Code of Nomenclature for algae, fungi and plants resulted in the move to one name per species, meaning that a decision had to be made whether to keep Aspergillus as one big genus or to split it into several smaller genera. The International Commission of Penicillium and Aspergillus decided to keep Aspergillus instead of using smaller genera. In this paper, we present the arguments for this decision. We introduce new combinations for accepted species presently lacking an Aspergillus name and provide an updated accepted species list for the genus, now containing 339 species. To add to the scientific value of the list, we include information about living ex-type culture collection numbers and GenBank accession numbers for available representative ITS, calmodulin, β-tubulin and RPB2 sequences. In addition, we recommend a standard working technique for Aspergillus and propose calmodulin as a secondary identification marker.

Keywords: Fungal identification; Media; Nomenclature; Phylogeny.

Fig. 1

Range of conidiophore phenotypes, which phylogenetically belong in Aspergillus. A, B. Basipetospora halophila (CBS 232.32). C, D. Dichotomomyces cejpii (CBS 157.66). E. Phialosimplex sp. (WL04MI-422). F. Phialosimplex caninus (CBS 128032). G, H. Polypaecilum insolitum (CBS 384.61). I. Diminutive conidiophores in Aspergillus arenarioides (CBS 138200). J, K. Diminutive conidiophores in A. subalbidus (CBS 567.65). L, O. Aspergillus sloanii (CBS 138177). M, N. Aspergillus ochraceus (CBS 108.08). Scale bars: A–O = 10 μm.

Fig. 2

Flow diagram summarising recommended methods for the identification and characterisation of Aspergillus. Frisvad & Thrane (1987, 1993), Smedsgaard (1997) and Klitgaard et al. (2014), refer to methods described for detecting extrolites in fungi.

Fig. 3

Phylogenetic tree obtained with 188 polymorphic sites and fixed SNPs (conserved in spp.) derived from the calmodulin sequences of strains representative of the genetic variability of the 25 recognised species in Aspergillus section Nigri (* = type strains).

Fig. 4

Combined phylogeny of the RPB2, Cct8 and Tsr1 gene regions showing the phylogenetic position of P. inflatum (≡ A. inflatus) in Aspergillus sect. Cremei. The tree was rooted to Talaromyces flavus. Branches with bootstrap support above 80 % and/or posterior probability above 0.95 are given above thickened branches.

Fig. 5

Aspergillus inflatus. A. Colonies on CYA. B. Colonies on MEA. C. Colonies on CREA. D–H. Conidiophores. I. Conidia. Scale bars: D–I = 10 μm.