Chemogenomic profiling in yeast reveals antifungal mode-of-action of polyene macrolactam auroramycin

Abstract

In this study, we report antifungal activity of auroramycin against Candida albicans , Candida tropicalis , and Cryptococcus neoformans . Auroramycin, a potent antimicrobial doubly glycosylated 24-membered polyene macrolactam, was previously isolated and characterized, following CRISPR-Cas9 mediated activation of a silent polyketide synthase biosynthetic gene cluster in Streptomyces rosesporous NRRL 15998. Chemogenomic profiling of auroramycin in yeast has linked its antifungal bioactivity to vacuolar transport and membrane organization. This was verified by disruption of vacuolar structure and membrane integrity of yeast cells with auroramycin treatment. Addition of salt but not sorbitol to the medium rescued the growth of auroramycin-treated yeast cells suggesting that auroramycin causes ionic stress. Furthermore, auroramycin caused hyperpolarization of the yeast plasma membrane and displayed a synergistic interaction with cationic hygromycin. Our data strongly suggest that auroramycin inhibits yeast cells by causing leakage of cations from the cytoplasm. Thus, auroramycin’s mode-of-action is distinct from known antifungal polyenes, reinforcing the importance of natural products in the discovery of new anti-infectives.

Antifungal and anti-mycotoxigenic activity of selected South African medicinal plants species

“…The mode of action of the compounds may be through mycelial growth inhibition. However, other studies suggested that the compounds may act through cell membrane damage, compromising the integrity and permeability of fungal cells (Haraguchi et al., 1999; Leite et al., 2014) and possible leakage of cations from the cytoplasm (Wong et al., 2019).…”

Discovery, characterization, and engineering of an advantageous Streptomyces host for heterologous expression of natural product biosynthetic gene clusters

“…However, to our surprise, the production rates in R5 media were comparable between the CH and the latter S. coelicolor M1152 strain. To push the boundaries further, we selected the cryptic auroramycin BGC, spanning approximately 106 kb, from S. roseosporus NRRL 15 998 [46,58]. Using our recently described CAP-TURE method [22] and from our in-house strain library, we cloned and expressed this BGC heterologously.…”

Polyene Macrolactams from Marine and Terrestrial Sources: Structure, Production Strategies, Biosynthesis and Bioactivities

“…Auroramycin (37) was a rare member of polyene macrolactams with antifungal bioactivity. The action of auroramycin in yeast cells was that it disrupted the structural organization of the vacuolar and the integrity of membranes, which differed from amphotericin B. Auroramycin was able to cause ionic stress and hyperpolarization of the yeast plasma membrane, which resulted in the microcosmic phenomenon of cation leakage from the cytoplasm [134].…”