Aspergillus niger forms conidia that contain melanin in their cell wall. This black pigment has been shown to protect fungi against UV-radiation and experimental evidence has indicated that it also protects against drought and high salt concentrations. In this study, growth of A. niger was evaluated at low water activity (aw ) and after changes in relative humidity (RH). In addition, deletion strains of A. niger affected in the melanin synthesis pathway were compared. Germination of conidia of the wild-type and deletion strains was observed at 0.81 aw and germ tubes continued growth at aw ≥ 0.83. Conidia and micro-colonies of the different strains were incubated for 1 week at lowered RH (33-84%). Conidia of all strains germinated and formed colonies after exposure to RH ≥ 33% when transferred back to malt extract medium at aw 0.98. Conidia germinated and showed limited growth at 84% RH. Micro-colonies of all strains did not survive an incubation of 1-week at RH ≤ 75%, but continued growth after exposure to 84% RH. Together, this is the first genetic evidence that melanin does not play a role during germination and radial extension of fungi at low water conditions. This article is protected by copyright. All rights reserved.
- Journal Article