Secondary metabolites produced by fungi derived from a microbial mat encountered in an iron-rich natural spring

Abstract

A collection of fungal isolates was obtained from a complex microbial mat, which occupied an iron-rich freshwater spring that feeds into Clear Creek, Golden, Colorado, USA. Two of the fungal isolates, a Glomeromycete (possible Entrophospora sp.) and a Dothideomycete (possible Phaeosphaeria sp.), were investigated for bioactive secondary metabolites. In total, six new compounds consisting of clearanols A–E (5, 6, 10–12) and disulochrin (7) were purified and their structures were determined. Disulochrin exhibited modest antibacterial activity against methicillin-resistant Staphylococcus aureus, whereas clearanol C showed weak inhibitory activity against Candida albicans biofilm formation.

Secondary metabolites from the endolichenic fungusOphiosphaerella korrae

“…Compound 9 was isolated as massive colourless crystals. The NMR proles of 9 were exactly consistent with those of the known compound clearanol E, 20 which was rst isolated as a 1 : 1 mixture with clearanol D from two of the fungal isolates [a glomeromycete (possibly Entrophospora sp.) and a dothideomycete (possibly Phaeosphaeria sp.)].…”

“…Compounds 6-8, 10 and 13 were dissolved in DMSO to a concentration of 40 mg mL À1 . Then, different volumes (1.25, 2.5, 5, 10 and 20 mL) of each solution were added to 10 mL of 1/2 MS medium to obtain plates with different concentrations of compounds (5,10,20,40 and 80 mg mL À1 ). To eliminate the effect of DMSO on the growth of A. thaliana, plates with the same volumes of DMSO were used as blank controls.…”

Active Metabolites from Endolichenic Fungus Talaromyces sp.

“…The structure of 2 (colorless crystals) was confirmed as clearanol A [11,12] by means of spectroscopic (NMR and MS) analysis. The NMR data of 2 were also provided in Table 1 and in the Supporting Information because no reference was available concerning those data.…”

Recent advances in natural product discovery

“…Often, these stresses come from interspecies interactions across all three domains of life, and so sampling particularly diverse environments and intimate interactions can lead to the discovery of new and interesting compounds. For example, isolation of two fungi from a microbial mat in an iron-rich spring led to the characterization of six novel natural products: clearanols A-E and disulochrin [3]. In particular, endosymbiotic bacteria represent a rich source of natural products [4], as many higher organisms rely on them to supplement their own defense systems.…”