An Antifungal Role of Hydrogen Sulfide on the Postharvest Pathogens Aspergillus niger and Penicillium italicum

et al. (2014) An Antifungal Role of Hydrogen Sulfide on the Postharvest Pathogens Aspergillus niger and Penicillium italicum. PLoS ONE 9(8): e104206. doi:10.1371/journal.pone.0104206 An Antifungal Role of Hydrogen Sulfide on the Postharvest Pathogens Aspergillus niger and Penicillium italicum Liu-Hui Fu 0 Kang-Di Hu 0 Lan-Ying Hu 0 Yan-Hong Li 0 Liang-Bin Hu 0 Hong Yan 0 Yong-Sheng Liu 0 Hua Zhang 0 John Calvert, Emory University, United States of America 0 1 School of Biotechnology and Food Engineering, Hefei University of Technology , Hefei , China , 2 School of Food Science, Henan Institute of Science and Technology , Xinxiang , China , 3 College of Chemical and Environmental Engineering, Harbin University of Science and Technology, Key Laboratory of Green Chemical Technology of College of Heilongjiang Province , Harbin , China In this research, the antifungal role of hydrogen sulfide (H2S) on the postharvest pathogens Aspergillus niger and Penicillium italicum growing on fruits and under culture conditions on defined media was investigated. Our results show that H2S, released by sodium hydrosulfide (NaHS) effectively reduced the postharvest decay of fruits induced by A. niger and P. italicum. Furthermore, H2S inhibited spore germination, germ tube elongation, mycelial growth, and produced abnormal mycelial contractions when the fungi were grown on defined media in Petri plates. Further studies showed that H2S could cause an increase in intracellular reactive oxygen species (ROS) in A. niger. In accordance with this observation we show that enzyme activities and the expression of superoxide dismutase (SOD) and catalase (CAT) genes in A. niger treated with H2S were lower than those in control. Moreover, H2S also significantly inhibited the growth of Saccharomyces cerevisiae, Rhizopus oryzae, the human pathogen Candida albicans, and several food-borne bacteria. We also found that short time exposure of H2S showed a microbicidal role rather than just inhibiting the growth of microbes. Taken together, this study suggests the potential value of H2S in reducing postharvest loss and food spoilage caused by microbe propagation. - Funding: This work was supported by the Natural Science Foundation of China (31271803 to LYH, 31301820 to HZ, 31300133 to KDH) http://www.nsfc.gov.cn/, the Scientific Research Foundation for the Returned Overseas Chinese Scholars (SRF for ROCS, SEM to HZ), the Natural Science Foundations of Anhui Province (11040606M85 to HZ) and the Anhui Provincial Education Department (2012AJZR0028 to HZ). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. . These authors contributed equally to this work. Generally, about 20% of harvested fruits and vegetables undergo decay during postharvest storage [1]. Considerable postharvest decay is caused by plant fungal pathogens [2]. It has been reported that Aspergillus niger can induce the spoilage of fruits such as cherry tomatoes and grapes, and Penicillium italicum can cause postharvest blue mold of citrus fruit [3,4,5]. Decay caused by food-borne bacterial pathogens AR also a major concern due to the increasing demands for food safety [6]. For instance, both Salmonella typhimurium and Staphylococcus aureus in contaminated food are leading causes of gastroenteritis [7,8]. The application of synthetic chemical as germicides is a primary method to control postharvest decay [9]. However, chemical control faces two intractable problems: first, the inevitable development of pathogen resistance; and second, a range of generally used germicides are under review in many countries due to health safety issues [10]. Thus, there is a growing need to develop alternative treatments of postharvest disease that are more enduring and safe. Hydrogen sulfide (H2S), traditionally thought as a toxic gas, has proved to be a gaseous signaling molecule after nitric oxide and carbon monoxide in animals [11]. Accumulating evidence shows multiple roles of H2S in plant development, abiotic stresses, and postharvest senescence [12,13,14,15,16]. Nitric oxide has also been shown to extend postharvest storage of fruits and to inhibit the growth of postharvest pathogens [17,18]. Lai et al. [19] found that the inhibitory effect of NO on the spores of Penicillium expansum was associated with oxidative damage. Similarly, it has been found that exogenous H2S application can prolong postharvest storage of strawberry, fresh-cut kiwifruit, broccoli and mulberry fruit by modulating the antioxidant system [15,20,21,22]. The concentration of the applied H2S required to delay senescence in strawberry is quite low, indicating that fumigation of fruits with H2S gas could be safe and practical [15]. However, there is limited data on the relations between H2S and postharvest pathogens. The earliest related research on this topic was reported by Marsh [23] who found that H2S was toxic to germinating spores of Sclerotinia fructicola. Recently, Hu et al. [24] showed that H2S could prolong postharvest storage of freshcut pears and inhibit fungal growth, although the underlining mechanism of the antifungal role of H2S is unknown. In this work, we investigated the antifungal effect of H2S on the postharvest pathogens A. niger and P. italicum inoculated on fruits, as well as on the growth of these fungi on Petri dishes with defined media. We also examined the effect of H2S on bakers yeast (Saccharomyces cerevisiae), Rhizopus oryzae, the human pathogen Candida albicans, and several food-borne bacteria, including Staphyloccocus aureus, Salmonella typhimurium, Listeria monocytogenes, Bacillus subtilis, Bacillus thuringiensis, Escherichia coli and Enterobacter aerogenes. Materials and methods Materials Six different fruits, apple (Malus domestica), kiwifruit (Actinidia deliciosa), pear (Pyrus bretschneideri Rehd.), sweet orange (Citrus sinensis), mandarin (Citrus reticulata) and tomato (Lycopersicon esculentum), used in this work were supplied by a fruit market in Hefei, Anhui province, China. Unwounded and healthy fruits, all of a similar size and maturity, were selected for experimentation. Pure fungal and bacterial isolates used in this research were kindly supplied by School of Biotechnology and Food Engineering, Hefei University of Technology, Anhui, Peoples Republic of China, except Candida albicans (SC5314) which was kindly bestowed by Prof. Jianli Sang at College of Life Science, Beijing Normal University. Three molds (Aspergillus niger, Penicillium italicum, Rhizopus oryzae), two yeasts (Saccharomyces cerevisiae, Candida albicans) and seven bacteria (Staphyloccocus aureus, Salmonella typhimurium, Listeria monocytogenes, Bacillus subtilis, Bacillus thuringiensis, Escherichia coli and Enterobacter aerogenes) were used in this study. Molds, yeasts and bacteria were cultured on potato dextrose agar ( (...truncated)