Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architectur and Technology, Xi'an 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
Key Laboratory of Northwest Water Resource, Environment and Ecology, MOE, Xi'an University of Architectur and Technology, Xi'an 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
Water Res. 2022 Sep 1;223:119039. doi: 10.1016/j.watres.2022.119039. Epub 2022 Aug 30.
Melanin is a critical component of fungal cell wall which protect fungi from adverse environmental tress. However, the role of melanin for fungi during the disinfection with chlorine-based disinfectants has not been elucidated. The results showed that the inactivation rate constants of Aspergillus niger with chlorine and chlorine dioxide decreased from 0.08 to 2.10 min to 0 after addition of 0.32 mg/L melanin. The results indicated addition of extracted fungal melanin inhibited the inactivation efficiency of chlorine and chlorine dioxide. In contrast, the k of Aspergillus niger after inactivation with monochloramine ranged from 1.50 to 1.78 min after addition of melanin which indicated effect of melanin on the inactivation efficiency of monochloramine was negligible. In addition, the extracted fungal melanin exhibited high reactivity with chlorine and chlorine dioxide but very low reactivity with monochloramine. The different inactivation mechanisms of chlorine-based disinfectants and different reactivity of melanin with chlorine-based disinfectants led to the different protective mechanism of melanin for A. niger and A. flavus spores against disinfection with chlorine-based disinfectants. The chlorine and chlorine dioxide appeared to react with functional groups of melanin in cell wall of spores, so sacrificial reactions between melanin and disinfectants decreased the available disinfectants and limited the diffusion of disinfectants to the reactive site on cell membrane, which led to the decrease of the disinfection efficiency for chlorine and chlorine dioxide. The monochloramine could penetrate into cell and damage DNA without the effect of melanin due to its strong penetration and low reactivity with melanin. Our results systematically demonstrate the protective roles of melanin on the fungal spores against chlorine-based disinfectants and the underlying mechanisms in resisting the environmental stress caused by chlorine-based disinfectants, which provides important implications for the control of fungi, especially for fungi producing melanin.
黑色素是真菌细胞壁的关键组成部分，可保护真菌免受不利环境压力的影响。然而，黑色素在真菌受到含氯消毒剂消毒时的作用尚未阐明。结果表明，在添加 0.32mg/L 黑色素后，黑曲霉的氯和二氧化氯灭活速率常数从 0.08 到 2.10 分钟减少到 0。结果表明，提取的真菌黑色素抑制了氯和二氧化氯的灭活效率。相比之下，在添加黑色素后，黑曲霉经单氯胺灭活后的 k 值在 1.50 到 1.78 分钟之间，表明黑色素对单氯胺灭活效率的影响可以忽略不计。此外，提取的真菌黑色素与氯和二氧化氯表现出高反应性，而与单氯胺的反应性非常低。含氯消毒剂的不同灭活机制和黑色素与含氯消毒剂的不同反应性导致黑色素对黑曲霉和黄曲霉孢子的保护机制不同，以抵抗含氯消毒剂的消毒。氯和二氧化氯似乎与孢子细胞壁中黑色素的功能基团发生反应，因此黑色素与消毒剂之间的牺牲反应减少了可用消毒剂的数量，并限制了消毒剂向细胞膜反应部位的扩散，从而降低了氯和二氧化氯的消毒效率。由于单氯胺具有很强的穿透性和与黑色素的低反应性，因此可以穿透细胞并破坏 DNA，而不受黑色素的影响。我们的研究结果系统地证明了黑色素对真菌孢子的保护作用以及黑色素抵抗含氯消毒剂引起的环境压力的潜在机制，这为控制真菌，特别是产生黑色素的真菌，提供了重要的启示。
