The role of oxidative stress in the growth of the indoor mold Cladosporium cladosporioides under water dynamics

Moisture is one of the critical abiotic factors that can affect mold growth. Indoor humidity is typically fluctuating, which renders a transient water supply for mold growth. Understanding mold growth under water dynamics and its underlying mechanisms can help in the development of novel and sustainable mold prevention strategies. In this study, pre-germination and germinated spores of Cladosporium cladosporioides were exposed to daily wet-dry cycles with different combinations of wetting and drying duration. Afterward, growth delay, cellular H₂O₂ concentration, and catalase (CAT) activity were measured and compared. We found that under daily wet-dry cycles, the longer the growth delay was observed, the higher the cellular H₂O₂ concentration was detected, with the 12-12 wet-dry cycle (12-hour wet and 12-hour dry) showing the longest growth delay and highest cellular H₂O₂ production. A positive correlation between cellular H₂O₂ concentration and growth delay was suggested by Pearson correlation coefficient and linear regression analysis (P <.0001, R² = 0.85). Furthermore, under daily wet-dry cycles, molds derived from pre-germination spores generally exhibited shorter growth delay, lower cellular H₂O₂ concentration, and higher CAT activity than molds developed from germinated spores. These results together suggest that the growth delay of C. cladosporioides under water dynamics is associated with oxidative stress.