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Rediscovery of viomellein as an antibacterial compound and identification of its biosynthetic gene cluster in dermatophytes

Summary

Researchers discovered that skin-infecting fungi called dermatophytes produce a red pigment called viomellein that kills bacteria. By studying the genes responsible for making viomellein, scientists found that this compound may help dermatophytes establish infections by eliminating competing bacteria on the skin. This discovery could explain how these fungi successfully colonize human skin and may lead to new treatment strategies for stubborn fungal infections.

Background

Dermatophytes are widespread human pathogens affecting over one billion people worldwide. While interactions between dermatophytes and skin microbiota are crucial for infection, little is known about the chemical basis of dermatophyte-bacteria interactions at infection sites.

Objective

To identify antibacterial compounds produced by dermatophytes and characterize their biosynthetic genes, particularly focusing on understanding the chemical interactions between dermatophytes and commensal bacteria during infection.

Results

Viomellein was rediscovered as the main antibacterial pigment produced by Trichophyton rubrum and other dermatophytes. The vio gene cluster consisting of nine genes was identified and characterized. Sequential reconstruction of vio cluster genes revealed biosynthetic pathway via nor-toralactone, semivioxanthin, and vioxanthin. Viomellein showed potent activity against gram-positive bacteria including Staphylococcus aureus with MIC of 0.78 µg/mL.

Conclusion

Dermatophytes produce diverse naphthopyranone compounds with strong antibacterial activity, suggesting viomellein production may be an initial infection strategy. The vio gene cluster is conserved across dermatophyte species and is also present in Aspergillus and Penicillium species, providing insight into microbial interactions at infection sites.
  • Published in:Applied and Environmental Microbiology,
  • Study Type:Experimental Research Study,
  • Source: 10.1128/aem.02431-24, PMID: 40197033
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