Data_Sheet_4_The trade-off of Vibrio parahaemolyticus between bacteriophage resistance and growth competitiveness.xlsx

Vibrio parahaemolyticus is a food-borne pathogen, which is often isolated from various seafood products. In this study, two kinds of bacteriophages was isolated from the offshore sediments samples. The anti-phage mutant strain were obtained after seventeen rounds of co-culture of Vibrio parahaemolyticus and mixed bacteriophage, multigroup sequencing was carried out on spontaneous the anti-phage mutant strain and the wild-type strain. We used the Sanger sequencing to verify the accuracy of the mutation sites. Biolog GEN III MicroPlates were used to evaluate the metabolic capacity of wild-type strains and the anti-phage mutant strain. In this study, we found that with flaG gene (slight homology to N terminus of multiple flagellins) mutated, making the bacteriophage unable to absorb to the cell surface of the host. And, the growth competitiveness of the anti-phage mutant strain is lower than the wild-type strain. These results indicated that the fitness cost, including loss of the growth competitiveness, constitutes a barrier to the prevalence of these defense mechanisms. And the selection pressure on different anti-phage strategies depends on the trade-off between mortality imposed by bacteriophages and fitness cost of the defense strategy under the given environmental conditions. In conclusion, this study provides valuable insights into the phage-host interaction and phage resistance in Vibrio parahaemolyticus. Our study provided knowledge for the evolutionary adaption of bacteria against the bacteriophage, which could add more information to understand the phage resistance mechanism before applying in the industry.

副溶血性弧菌（Vibrio parahaemolyticus）是一种食源性致病菌，常从各类海产品中分离得到。本研究从近海沉积物样本中分离得到两株噬菌体（bacteriophages）。将副溶血性弧菌与混合噬菌体共培养十七轮后，获得了抗噬菌体突变株（anti-phage mutant strain）；对自发抗噬菌体突变株与野生型菌株进行了多组测序，并采用桑格测序（Sanger sequencing）验证了突变位点的准确性。采用Biolog GEN III微孔板（Biolog GEN III MicroPlates）评估了野生型菌株与抗噬菌体突变株的代谢能力。本研究发现，当flaG基因（与多种鞭毛蛋白N端具有微弱同源性）发生突变时，噬菌体无法吸附至宿主细胞表面；且抗噬菌体突变株的生长竞争力低于野生型菌株。上述结果表明，包括生长竞争力丧失在内的适合度成本（fitness cost）构成了这类防御机制传播的障碍。而在特定环境条件下，不同抗噬菌体策略所承受的选择压力，取决于噬菌体介导的宿主死亡率与防御策略的适合度成本之间的权衡（trade-off）。综上，本研究为副溶血性弧菌的噬菌体-宿主互作及噬菌体抗性机制提供了重要见解。本研究为细菌对抗噬菌体的进化适应提供了理论依据，可为工业应用前深入解析噬菌体抗性机制补充更多研究数据。