Physiological responses of Aspergillus niger challenged with itraconazole

Aspergillus niger is an opportunistic pathogen commonly found in a variety of indoor and outdoor environments. Environmental isolates of A. niger taken from a pig farm were resistant to itracon-azole and in-depth investigations were conducted to better understand cellular responses during growth when exposed to an antifungal. Using a combination of cultivation techniques, antibiotic stress-testing, and label-free prote-omics, this study has investigated the physiological and metabolic responses of A. niger to suble-thal levels of antifungal stress. Challenging A. niger with itraconazole inhibited the growth, and the minimum inhibitory con-centration (MIC) was estimated to be >16 mg?L-1. Through the proteome analysis, 1305 unique proteins were identified. Differential expressed proteins during growth at 2 and 8 mg?L-1 itracona-zole revealed that a total of 91 and 50 proteins were significantly differentially expressed, respec-tively. Challenged with itraconazole, A. niger decreased the expression of peroxidative enzymes, increased the expression of an ATP-binding cassette (ABC) transporter most likely involved as an efflux pump, and inhibited ergosterol synthesis. Furthermore, a reduced expression of proteins involved in the production of ATP and reducing power from both TCA and glyoxylate cycle was ob-served. The mode of action of azoles in A. niger therefore appears more complex than previously anticipated and showcase future targets for antifungal treatment.