Thermoascus aurantiacus produces a thick, crusty, golden-brown colony on agar. The crusty appearance is due to the presence of many cleistothecia (closed ascocarps) which contain asci. Within each ascus is a cluster of 8 ascospores, shown in different stages of maturity (bottom right). From FUNGAL BIOLOGY: A Textbook by JIM DEACON Blackwell Publishing 2005. Courtesy of Jim Deacon, The University of Edinburgh.

Thermoascus aurantiacus is a thermophilic fungus in Eurotiales that has been examined extensively for its ability to secrete large amounts of thermostable enzymes for the depoymerization of cellulose and hemicellulose from plant biomass (Biotechnology for Biofuels, 2012, 5, 54). T. aurantiacus has been a key source of AA9 (formerly GH61) proteins, which function as polysaccharide monooxygenases and complement the well-studied hydrolytic depolymerization enzymes. Detailed characterization of T. aurantiacus AA9 has demonstrated that it has a copper-containing active site with an unusual methylated histidine bound to the copper (PNAS, 2011, 108, 15079). Sequencing of T. aurantiacus will provide key insights into the expression of these important polysaccharide deconstructing enzymes and allow T. aurantiacus to be a used as platform for the production of thermophilic enzymes.