Ban Ga-Hee, Dai Yue, Huan Tao, Ke Alfred, Delaquis Pascal, Wang Siyun
Food, Nutrition and Health, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, British Columbia, Canada.
Department of Chemistry, Faculty of Science, The University of British Columbia, Vancouver, British Columbia, Canada.
mSystems. 2021 Feb 9;6(1):e00898-20. doi: 10.1128/mSystems.00898-20.
Sprouts are the leading cause of foodborne disease outbreaks globally, mainly because the specialized conditions required to germinate seed sprouts for human consumption contribute to an environment that allows pathogenic bacteria to flourish. To reduce risk of illness, current food safety guidelines in the United States and Canada recommend hypochlorite treatment for seed sanitation. However, many growers and consumers have become wary of the impact of hypochlorite on human health and the environment and are actively seeking less caustic approaches. Here, we evaluated the effects of both the traditional hypochlorite treatment and a milder alternative on nontyphoidal colonization of germinating alfalfa seed. Moreover, we explored three biological factors as potential contributors for inhibition of growth: colonization by indigenous bacteria, seed composition changes, and seed metabolite release. In this experimental setting, we found that a combinatorial treatment of heat, peroxide, and acetic acid was as effective as hypochlorite for inhibiting growth. Notably, we pinpointed -acetyl-spermidine as an endogenous metabolite exuded by treated seeds that strongly inhibits growth. In doing so, we both elucidated one of the mechanisms of chemical sanitation and highlighted a potential seed-derived mode of antimicrobial treatment that may apply to modernized food safety protocols. Warm, humid, and nutrient-rich conditions that are used to produce sprouts encourage to proliferate. However, many disparate sanitation methods exist, and there is currently no single treatment that can guarantee pathogen-free seeds. Here, we compared the ability of traditional hypochlorite treatment against a combinatorial treatment of heat, peroxide, and vinegar (HPA) commonly used in organic farming practices to inhibit colonization and growth during alfalfa germination and found HPA to be at least as effective. Furthermore, we explored seed-based changes following sanitization treatments using metabolomics and identified polyamines as strong inhibitors of growth on germinating alfalfa. Our findings enable a better understanding of host-pathogen interactions in sprout microbial communities and promote in-depth, evidence-based research in seed sprout safety.
豆芽是全球食源性疾病爆发的主要原因，主要是因为将种子发芽以供人类食用所需的特殊条件营造了一个使致病细菌得以大量繁殖的环境。为降低患病风险，美国和加拿大目前的食品安全指南建议使用次氯酸盐处理种子以进行卫生处理。然而，许多种植者和消费者开始担心次氯酸盐对人类健康和环境的影响，并积极寻求腐蚀性较小的方法。在此，我们评估了传统次氯酸盐处理和一种较温和替代方法对发芽苜蓿种子非伤寒菌定植的影响。此外，我们探究了三种生物学因素作为抑制生长的潜在因素：本土细菌的定植、种子成分变化和种子代谢物释放。在本实验环境中，我们发现热、过氧化物和乙酸的组合处理在抑制生长方面与次氯酸盐一样有效。值得注意的是，我们确定N-乙酰亚精胺是经处理种子分泌的一种内源性代谢物，它能强烈抑制生长。通过这样做，我们既阐明了化学卫生处理的机制之一，又突出了一种潜在的源自种子的抗菌处理模式，这种模式可能适用于现代化的食品安全协议。用于生产豆芽的温暖、潮湿和营养丰富的条件会促使细菌大量繁殖。然而，存在许多不同的卫生处理方法，目前没有一种单一处理方法能保证种子无病原体。在此，我们比较了传统次氯酸盐处理与有机农业实践中常用的热、过氧化物和醋（HPA）组合处理在抑制苜蓿发芽过程中细菌定植和生长方面的能力，发现HPA至少同样有效。此外，我们使用代谢组学探究了卫生处理后基于种子的变化，并确定多胺是发芽苜蓿上细菌生长的强抑制剂。我们的研究结果有助于更好地理解豆芽微生物群落中宿主与病原体的相互作用，并促进对种子豆芽安全性进行深入的、基于证据的研究。
