Journal
APPLIED MICROBIOLOGY AND BIOTECHNOLOGY
Volume 102, Issue 5, Pages 2337-2350Publisher
SPRINGER
DOI: 10.1007/s00253-018-8792-0
Keywords
Adenylation domain; Antifungal; Ascomycota; Coprophilous fungi; Genome; Hypocreales; Nonribosomal peptide; synthetase; Secondary metabolites; Thermal adaption
Categories
Funding
- University of Texas Health Science Center at Houston
- Kay and Ben Fortson Endowment
- Chinese Scholarship Council
- NIH [R01GM121458]
- NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES [R01GM121458] Funding Source: NIH RePORTER
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We used a temperature differential assay with the opportunistic fungal pathogen Cryptococcus neoformans as a simple screening platform to detect small molecules with antifungal activity in natural product extracts. By screening of a collection extracts from two different strains of the coprophilous fungus, Amphichorda felina, we detected strong, temperature-dependent antifungal activity using a two-plate agar zone of inhibition assay at 25 and 37 A degrees C. Bioassay-guided fractionation of the crude extract followed by liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance spectroscopy (NMR) identified cyclosporin C (CsC) as the main component of the crude extract responsible for growth inhibition of C. neoformans at 37 A degrees C. The presence of CsC was confirmed by comparison with a commercial standard. We sequenced the genome of A. felina to identify and annotate the CsC biosynthetic gene cluster. The only previously characterized gene cluster for the biosynthesis of similar compounds is that of the related immunosuppressant drug cyclosporine A (CsA). The CsA and CsC gene clusters share a high degree of synteny and sequence similarity. Amino acid changes in the adenylation domain of the CsC nonribosomal peptide synthase's sixth module may be responsible for the substitution of l-threonine compared to l-alpha-aminobutyric acid in the CsA peptide core. This screening strategy promises to yield additional antifungal natural products with a focused spectrum of antimicrobial activity.
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