Characteristics of D-Tryptophan as an Antibacterial Agent: Effect of Sodium Chloride Concentration and Temperature on Escherichia coli Growth Inhibition
Characteristics of D-Tryptophan as an Antibacterial Agent: Effect of Sodium Chloride Concentration and Temperature on Escherichia coli Growth Inhibition
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DOI：
10.4315/0362-028x.jfp-17-229
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发表时间：
2018-01-01
影响因子：
2
通讯作者：
Koseki, Shigenobu
中科院分区：
文献类型：
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作者：
Kan, Kaito;Chen, Jian;Koseki, Shigenobu
我们以前报道，D-色氨酸表现出不利影响细菌生理渗透胁迫下。然而，D-色氨酸作为细菌生长的抑制剂和/或不相容溶质的机制尚未详细研究。在这项研究中，我们的目的是确定渗透压和温度如何影响D-色氨酸的抗菌效果。即使在相同的渗透压水平下，D-色氨酸与氯化钠（NaCl）一起对大肠杆菌的生长具有比与氯化钾（KCl）和蔗糖孵育所获得的更强的抑制作用。由于D-色氨酸与NaCl的组合表现出最强的抑制作用，我们确定了D-色氨酸和NaCl的最佳浓度组合。通过逻辑回归模型确定作为D-色氨酸和NaCl浓度的函数的生长抑制边界条件。我们发现，E.大肠杆菌生长抑制率为2.5%（w/v），与40 mM D-色氨酸一起。此外，NaCl浓度越高，抑制细菌生长所需的D-色氨酸浓度越低。我们开发的逻辑回归模型使我们能够预测抑制细菌生长所需的浓度。此外，我们研究了15至46 ℃范围内的孵育温度对D-色氨酸的抗菌作用的影响。反应温度越高，活菌数下降越快。大肠杆菌进行了观察。这种趋势可能是由于在最佳生长温度下生理代谢的激活。总之，我们的研究结果应作出重大贡献的发展一种新的细菌生长控制策略使用D-色氨酸。
We previously reported that D-tryptophan exhibits adverse effects on bacterial physiology under osmotic stress. However, the mechanism by which D-tryptophan acts as an inhibitor and/or incompatible solute for bacterial growth has not yet been investigated in detail. In this study, we aimed to determine how osmotic pressure and temperature affect the antimicrobial effect of D-tryptophan. Even at the same level of osmotic pressure, D-tryptophan in conjunction with sodium chloride (NaCl) had a stronger inhibitory effect on the growth of Escherichia coli than that obtained by incubation with potassium chloride (KCl) and sucrose. Because D-tryptophan with NaCl showed the strongest inhibitory effect, we determined the optimum concentration combination of D-tryptophan and NaCl. The growth inhibition boundary conditions as a function of D-tryptophan and NaCl concentrations were determined by a logistic regression model. We found that the minimum level of NaCl for E. coli growth inhibition was 2.5% (w/v) together with 40 mM D-tryptophan. Moreover, the higher the NaCl concentration, the lower the concentration of D-tryptophan that was needed to inhibit bacterial growth. The logistic regression model that we developed enabled us to predict the concentrations required to inhibit bacterial growth. Furthermore, we examined the effect of incubation temperatures ranging from 15 to 46 degrees C on the antimicrobial effect of D-tryptophan. The higher the reaction temperature, the more rapid the decrease of viable E. coli that was observed. This trend is likely attributable to activation of physiological metabolism under the optimum growth temperature. Together, our findings should make a significant contribution to the development of a novel bacterial growth control strategy using D-tryptophan.