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The role of melanin in Aspergillus tolerance to biocides and photosensitizers
Author(s) -
Pascoe M.J.,
Maillard J.Y.
Publication year - 2021
Publication title -
letters in applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.698
H-Index - 110
eISSN - 1472-765X
pISSN - 0266-8254
DOI - 10.1111/lam.13437
Subject(s) - biocide , microbiology and biotechnology , aspergillus , melanin , bacteria , biology , chemistry , biochemistry , genetics , organic chemistry
Abstract Cationic biocides are widely utilized for surface disinfection. Photosensitizers such as toluidine blue O (TBO) produce reactive oxygen species following light excitation and are being investigated as novel biocides for similar applications. Aspergillus brasiliensis conidia contain melanin which protects against environmental stressors. The negative charge and antioxidant properties of melanin may confer resistance to photosensitizers and other biocides. In this study, the yeasticidal and fungicidal activity benzalkonium chloride (BZC), sodium dichloroisocyanurate (NaDCC) and TBO with red light were examined using quantitative suspension tests. All three biocides were highly effective against Candida albicans and > 5·0 log 10 reductions in viability were attainable within 5 minutes. Wild‐type A. brasiliensis conidia were highly tolerant to treatment and 0·4 log 10 reductions in viability were observed within the same time frame when treated with TBO or BZC. NaDCC was markedly more effective. Inhibition of melanin biosynthesis by culturing with 100 μ g ml −1 kojic acid resulted in a hypopigmented phenotype with significantly increased sensitivity to all three biocides. These observations indicate that melanin is a significant contributor towards A. brasiliensis tolerance of biocides and photosensitizers and demonstrate that cationic biocides are poorly suited to applications where the control of A. brasiliensis is required.