Date Published: April 5, 2017
Publisher: Public Library of Science
Author(s): John I. Pitt, Lene Lange, Alastair E. Lacey, Daniel Vuong, David J. Midgley, Paul Greenfield, Mark I. Bradbury, Ernest Lacey, Peter K. Busk, Bo Pilgaard, Yit-Heng Chooi, Andrew M. Piggott, Jae-Hyuk Yu.
Aspergillus hancockii sp. nov., classified in Aspergillus subgenus Circumdati section Flavi, was originally isolated from soil in peanut fields near Kumbia, in the South Burnett region of southeast Queensland, Australia, and has since been found occasionally from other substrates and locations in southeast Australia. It is phylogenetically and phenotypically related most closely to A. leporis States and M. Chr., but differs in conidial colour, other minor features and particularly in metabolite profile. When cultivated on rice as an optimal substrate, A. hancockii produced an extensive array of 69 secondary metabolites. Eleven of the 15 most abundant secondary metabolites, constituting 90% of the total area under the curve of the HPLC trace of the crude extract, were novel. The genome of A. hancockii, approximately 40 Mbp, was sequenced and mined for genes encoding carbohydrate degrading enzymes identified the presence of more than 370 genes in 114 gene clusters, demonstrating that A. hancockii has the capacity to degrade cellulose, hemicellulose, lignin, pectin, starch, chitin, cutin and fructan as nutrient sources. Like most Aspergillus species, A. hancockii exhibited a diverse secondary metabolite gene profile, encoding 26 polyketide synthase, 16 nonribosomal peptide synthase and 15 nonribosomal peptide synthase-like enzymes.
The fungal genus Aspergillus is a very important source of industrial enzymes and metabolic products as well as the major mycotoxins aflatoxin and ochratoxin A. During an ecological survey of Aspergillus species in the South Burnett region of Southeast Queensland in 1982, an unusual fungus was isolated from soil that had previously been under peanut cultivation. The isolate was conspicuous because it produced rapidly growing, floccose colonies, with very long conidiophores bearing spherical heads and forming elongate black sclerotia in age. These features were indicative of a species that would be classified currently in the A. alliaceus clade in Aspergillus subgenus Circumdati section Flavi, near A. leporis, but distinguished by producing green conidia. It was lost from our collection, but isolated again five years later from the same property. It was not isolated from any other locality in the South Burnett. More than 10 years later, we isolated other strains from a food sample (dried peas) in northwestern Victoria, and subsequently from uncultivated road side soil samples in southern NSW, over 1000 km south of the South Burnett region. It therefore has a widespread but sparse distribution in eastern Australia. Further examination showed that this species produced a unique DNA sequence and an unusually large range of secondary metobiltes, many of them unique. Using the genome sequence, it was also possible to study its production of carbohydrate degrading enzymes and the diversity of its secondary metabolite gene profile. This species is described in this paper as A. hancockii Pitt sp. nov.