ABSTRACT

Streptococcus suis

serotype 2 (SS2) is a serious zoonotic pathogen which causes symptoms of streptococcal toxic shock syndrome (STSS) and septicemia; these symptoms suggest that SS2 may have evade innate immunity. Phagocytosis is an important innate immunity process where phagocytosed pathogens are killed by lysosome enzymes, reactive oxygen, and nitrogen species, and acidic environments in macrophages following engulfment. A previously constructed mutant SS2 library was screened, revealing 13 mutant strains with decreased phagocytic resistance. Through inverse PCR, the transposon insertion sites were determined. Through bioinformatic analysis, the 13 disrupted genes were identified as Cps2F, 3 genes belonging to ABC transporters, WalR, TehB, rpiA, S-transferase encoding gene, prs, HsdM, GNAT family N-acetyltransferase encoding gene, proB, and upstream region of DnaK. Except for the capsular polysaccharide biosynthesis associated Cps2F, the other genes had not been linked to a role in anti-phagocytosis. The survival ability in macrophages and whole blood of randomly picked mutant strains were significantly impaired compared with wild-type ZY05719. The virulence of the mutant strains was also attenuated in a mouse infection model. In the WalR mutant, the transcription of HP1065 decreased significantly compared with wild-type strain, indicating WalR might regulated HP1065 expression and contribute to the anti-phagocytosis of SS2. In conclusion, we identified 13 genes that influenced the phagocytosis resistant ability of SS2, and many of these genes have not been reported to be associated with resistance to phagocytosis. Our work provides novel insight into resistance to phagocytosis, and furthers our understanding of the pathogenesis mechanism of SS2.

中文翻译：

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通过猪链球菌血清型2转座子突变文库筛选与吞噬作用相关的基因

摘要

猪链球菌

血清型2（SS2）是一种严重的人畜共患病原体，可引起链球菌中毒性休克综合征（STSS）和败血病的症状。这些症状表明SS2可能具有先天免疫力。吞噬作用是重要的先天免疫过程，吞噬后吞噬的病原体被溶酶体，活性氧和氮物种以及巨噬细胞中的酸性环境杀死。筛选了先前构建的SS2突变体文库，发现了13个具有降低的吞噬性的突变菌株。通过反向PCR，确定转座子插入位点。通过生物信息学分析，鉴定出13个被破坏的基因为Cps2F，3个属于ABC转运蛋白的基因，WalR，TehB，rpiA，S-转移酶编码基因，prs，HsdM，GNAT家族N-乙酰基转移酶编码基因，proB和DnaK的上游区域。除了荚膜多糖生物合成相关的Cps2F，其他基因尚未与抗吞噬作用有关。与野生型ZY05719相比，随机选择的突变株在巨噬细胞和全血中的生存能力显着受损。突变株的毒力在小鼠感染模型中也被减弱。在WalR突变体，转录HP1065与野生型菌株降低显著相比，表明WalR可能调节HP1065表达并有助于SS2的抗吞噬作用。总之，我们鉴定了13个影响SS2吞噬作用抗性能力的基因，而且尚未报道其中许多基因与抗吞噬作用有关。我们的工作为抵抗吞噬作用提供了新颖的见解，并进一步加深了我们对SS2发病机理的了解。