Genetic modification of an echinocandin B-producing strain ofAspergillus nidulans to produce mutants blocked in sterigmatocystin biosynthesis

Abstract

The production of echinocandin B (ECB), a lipopolypeptide used for chemical manufacture of the anti-Candida agent Cilofungin, was accomplished by fermentation using a strain of Aspergillus nidulans. In addition to ECB, this fermentation also produces a significant amount of sterigmatocystin (ST), a potent carcinogen structurally related to the aflatoxins. Mutants blocked in the ST biosynthetic pathway were created by genetic modification of the polyploid production strain C747. The following steps were involved: (i) reduction of the genotype to haploid by treatment with the spindle fiber poison methyl 1-(butylcarbamoyl)-2-benzimidazole carbamate (MBC), using colony morphology, conidia size, and the ability to obtain 5-fluoro-orotic acid (5-FOA)-resistant mutants as criteria for ploidy; (ii) mutagenesis of a haploid isolate using UV irradiation; and (iii) screening of mutants for inability to produce ST by thin layer chromatography. Six mutants blocked in ST production were isolated. All six remained capable of producing ECB equivalent in quantity to the haploid strain C747-GR14. One of the mutants was shown to be the result of a chromosomal translocation.

The Potential of Antimicrobial Peptides as Biocides

“…The cationic peptides histatins, derived from the saliva of humans, bind to receptors present on the fungal cell membrane and when present in the cytoplasm they target fungal mitochondria [200]. The echinocandins are an antimicrobial peptide family sourced from Aspergillus nidulans that includes the peptides anidulafungin caspofungin, and micafungin [201]. They have been shown to inhibit β-(1,3)-glucan synthase, an enzyme responsible for the production of the essential fungal cell wall component β-(1,3)-glucan [202–204].…”

Polyphasic characterization of “Aspergillus nidulans var. roseus” ATCC 58397

“…Besides ECB, A. nidulans var. roseus also produces the carcinogenic sterigmatocystin, which is chemically related to the wellknown aflatoxins (Hodges et al 1994).…”

Novidades Em Fármacos Antifúngicos: Uma Revisão

“…Desenvolvido pela Eli Lilly and Company. É derivada do antibiótico produzido pelo microrganismo Aspergillus nidulans (HODGES et al, 1994) equinocandina B (Fig.2), que tem a cadeia lateral substituída por outra de origem sintética. A modificação estrutural trouxe aumento na atividade antifúngica, além de diminuição no potencial hemolítico para o composto semi-sintético (DEBONO et al, 1995;TOMISHIMA et al, 1999).…”