Dept. of Marine Biology, Microbiology and Biochemistry, School of Marine Sciences, Lakeside Campus, Cochin Univ. of Science and Technology, Cochin, 682 016, Kerala, India.
J Food Sci. 2019 Aug;84(8):2250-2255. doi: 10.1111/1750-3841.14729. Epub 2019 Jul 17.
The ability to produce various extracellular enzymes is considered as an important virulence feature in Aeromonas spp., in addition to producing specific virulence factors such as aerolysin and hemolysin. In this study, the effect of salinity and pH on the production of extracellular virulence factors by Aeromonas was investigated. Aeromonas was obtained from different food sources. A comparative study of the activities of extracellular enzymes secreted by these bacteria at different environmental conditions can widen our understanding on their pathogenicity. The activities of various extracellular enzymes such as amylase, gelatinase, and caseinase, which are implicated as virulence factors, were measured in vitro by calculating the enzymatic activity index (EAI) of each enzyme using standard laboratory protocols. For all enzymes, a significant change (P < 0.05) in the EAI was observed when the concentration of NaCl in the media increased from 0.5% to 3%. Among three enzymes tested, caseinase was found to be affected the most by salinity, with a significant difference in EAI when NaCl concentration in the media increased from 0.5% to 2%. Similarly, amylase was found to be affected the most by acidity. The pH values ranging from 6 to 9 did not exert any significant change in EAI of amylase; however, a pH value of 5 had a significant effect. Overall, compared to salinity, the change in pH was found to be less effective in controlling the extracellular virulence factor production in Aeromonas. PRACTICAL APPLICATIONS: The practical application is to minimize the extracellular virulence factor production by Aeromonas in food commodities by altering the salt content and pH. The results demonstrate that an increase in salinity and a decrease in pH can minimize the extracellular virulence factor production by Aeromonas spp.
产生各种细胞外酶的能力被认为是气单胞菌属的重要毒力特征，除了产生特定的毒力因子，如 aerolysin 和溶血素。在这项研究中，研究了盐度和 pH 值对气单胞菌产生细胞外毒力因子的影响。气单胞菌从不同的食物来源获得。比较这些细菌在不同环境条件下分泌的细胞外酶的活性，可以加深我们对其致病性的理解。通过使用标准实验室方案计算每种酶的酶活性指数 (EAI)，在体外测量了各种细胞外酶（如淀粉酶、明胶酶和酪蛋白酶）的活性，这些酶被认为是毒力因子。对于所有酶，当培养基中 NaCl 浓度从 0.5%增加到 3%时，EAI 都观察到显著变化（P < 0.05）。在测试的三种酶中，发现酪蛋白酶受盐度影响最大，当培养基中 NaCl 浓度从 0.5%增加到 2%时，EAI 存在显著差异。同样，淀粉酶受酸度影响最大。pH 值在 6 到 9 范围内，淀粉酶的 EAI 没有发生任何显著变化；然而，pH 值为 5 时则有显著影响。总体而言，与盐度相比，pH 值的变化被发现对控制气单胞菌的细胞外毒力因子产生的影响较小。实际应用：通过改变盐含量和 pH 值，最大限度地减少食品中气单胞菌的细胞外毒力因子产生。结果表明，增加盐度和降低 pH 值可以最大限度地减少气单胞菌属的细胞外毒力因子产生。
