A new sterigmatocystin-producing Emericella variant from agricultural desert soils

Abstract

An unusual, sterigmatocystin-producing taxon with characteristics of both Emericella nidulans (anamorph Aspergillus nidulans) and Emericella rugulosa (anamorph Aspergillus rugulovalvus, formerly A. rugulosus) was isolated repeatedly during a mycofloral survey of desert cotton field soils where aflatoxin is a chronic problem. Members of this taxon had ascospores with smooth convex walls like E. nidulans but grew slowly like E. rugulosa; moreover, they were similar to an industrial echinocandin B-producing strain which had been classified as "Aspergillus nidulans var. roseus." These new desert isolates were compared with "A. nidufans var. roseus" and representative wild-type isolates of E. nidulans and E. rugulosa using traditional morphological characters, secondary metabolite profiles of mycelial extracts, and Southern blot analysis of genomic DNA. The desert isolates and "A. nidulans var. roseus" shared morphological, physiological and molecular characters with E. rugulosa. These isolates constitute a new non-rugulose variant of E. rugulosa.