Zhou Ziyao, Liu Furui, Zhang Xinyue, Zhou Xiaoxiao, Zhong Zhijun, Su Huaiyi, Li Jin, Li Haozhou, Feng Fan, Lan Jingchao, Zhang Zhihe, Fu Hualin, Hu Yanchun, Cao Suizhong, Chen Weigang, Deng Jiabo, Yu Jianqiu, Zhang Wenping, Peng Guangneng
The Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.
Chengdu Center for Animal Disease Prevention and Control, Chengdu, China.
PLoS One. 2018 Jan 31;13(1):e0191991. doi: 10.1371/journal.pone.0191991. eCollection 2018.
Surfactin secreted by Bacillus subtilis can confer strong, diverse antipathogenic effects, thereby benefitting the host. Carbon source is an important factor for surfactin production. However, the mechanism that bacteria utilize cellulose, the most abundant substance in the intestines of herbivores, to produce surfactin remains unclear. Here, we used B. subtilis HH2, isolated from the feces of a giant panda, as a model to determine changes in surfactin expression in the presence of different concentrations of cellulose by quantitative polymerase chain reaction and high-performance liquid chromatography. We further investigated the antimicrobial effects of surfactin against three common intestinal pathogens (Escherichia coli, Staphylococcus aureus, and Salmonella enterica) and its resistance to high temperature (60-121°C), pH (1-12), trypsin (100-300 μg/mL, pH 8), and pepsin (100-300 μg/mL, pH 2). The results showed that the surfactin expressed lowest in bacteria cultured in the presence of 1% glucose medium as the carbon source, whereas increased in an appropriate cellulose concentration (0.67% glucose and 0.33% cellulose). The surfactin could inhibit E. coli and Staphylococcus aureus, but did not affect efficiently for Salmonella enterica. The antibacterial ability of surfactin did not differ according to temperature (60-100°C), pH (2-11), trypsin (100-300 μg/mL), and pepsin (100-300 μg/mL; P > 0.05), but decreased significantly at extreme environments (121°C, pH 1 or 12; P < 0.05) compared with that in the control group (37°C, pH = 7, without any protease). In conclusion, our findings indicated that B. subtilis HH2 could increase surfactin expression in an appropriate cellulose environment and thus provide benefits to improve the intestinal health of herbivores.
枯草芽孢杆菌分泌的表面活性素具有强大且多样的抗病原体作用，从而使宿主受益。碳源是影响表面活性素产生的一个重要因素。然而，细菌利用纤维素（食草动物肠道中最丰富的物质）来产生表面活性素的机制仍不清楚。在此，我们以从大熊猫粪便中分离出的枯草芽孢杆菌HH2为模型，通过定量聚合酶链反应和高效液相色谱法来确定在不同浓度纤维素存在下表面活性素表达的变化。我们进一步研究了表面活性素对三种常见肠道病原体（大肠杆菌、金黄色葡萄球菌和肠炎沙门氏菌）的抗菌作用及其对高温（60 - 121°C）、pH值（1 - 12）、胰蛋白酶（100 - 300 μg/mL，pH 8）和胃蛋白酶（100 - 300 μg/mL，pH 2）的耐受性。结果表明，在以1%葡萄糖培养基作为碳源培养的细菌中，表面活性素表达最低，而在适当的纤维素浓度（0.67%葡萄糖和0.33%纤维素）下表达增加。表面活性素能够抑制大肠杆菌和金黄色葡萄球菌，但对肠炎沙门氏菌的抑制效果不佳。表面活性素的抗菌能力在温度（60 - 100°C）、pH值（2 - 11）、胰蛋白酶（100 - 300 μg/mL）和胃蛋白酶（100 - 300 μg/mL；P > 0.05）条件下没有差异，但与对照组（37°C，pH = 7，无任何蛋白酶）相比，在极端环境（121°C，pH 1或12；P < 0.05）下其抗菌能力显著下降。总之，我们的研究结果表明，枯草芽孢杆菌HH2在适当的纤维素环境中可增加表面活性素的表达，从而有助于改善食草动物的肠道健康。
