China Animal Husbandry and Veterinary Medicine ›› 2025, Vol. 52 ›› Issue (3): 1428-1436.doi: 10.16431/j.cnki.1671-7236.2025.03.043

• Basic Veterinary Medicine • Previous Articles    

Functional Study on SodA,TrxA and TrxC Genes of Streptococcus suis Type 2

LI Xi1, LIU Jianying2,3, FANG Lihua4, YIN Yulong2, TANG Yulong2   

  1. 1. Changsha Academy of Agricultural Sciences, Changsha 410023, China;
    2. Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China;
    3. College of Veterinary Medicine, Hunan Agricultural University, Changsha 410128, China;
    4. College of Bioscience and Biotechnology, Foshan University, Foshan 528225, China
  • Received:2024-07-24 Published:2025-02-22

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Abstract: 【Objective】 This study was conducted to investigate the biological functions of superoxide dismutase A (SodA),thioredoxin A (TrxA) and TrxC genes of Streptococcus suis type 2 in regulating oxidative stress and participating in pathogenic processes.【Method】 The regulation of stress resistance and virulence of 3 mutant strains of Streptococcus suis type 2,ΔSodA,ΔTrxA and ΔTrxC,were compared.The anti-oxidative stress ability of SodA,TrxA and TrxC genes to different oxidative stress treatments (0.04% hydrogen peroxide (H2O2),10 mol/L paraquat (PQ)) and the anti-temperature stress ability at different temperatures (4 and 43 ℃) were tested by stress survival test.Different gene deletion strains were co-cultured with porcine intestinal epithelial cells (IPEC-J2) and mouse macrophages (RAW264.7) to explore the effects of the 3 genes on cell adhesion and anti-phagocytosis.The effects of SodA,TrxA and TrxC genes on the anti-oxidative stress and the pathogenesis were investigated by testing the bacterial load,serum antioxidant enzymes and liver function in mice.【Result】 The results of anti-stress test showed that under different oxidative stress and different temperature stress conditions,the survival ability of ΔSodA and ΔTrxC strains was extremely significantly lower than that of wild strain (P＜0.01),and the survival ability of ΔTrxA strain was extremely significantly lower than that of wild strain under high temperature stimulation at 43 ℃ (P＜0.01).The results of cell adhesion test showed that the deletion of SodA and TrxA genes reduced the adhesion ability of bacteria by 55%-65%,which was extremely significantly lower than that of wild strain (P＜0.01).The results of anti-phagocytosis test showed that the survival rate of ΔSodA,ΔTrxC and ΔTrxA strains in phagocytosis cells was extremely significantly or significantly lower than that of wild strain (P＜0.01 or P＜0.05).The results of animal challenge test showed that the virulence of ΔSodA,ΔTrxA and ΔTrxC strains decreased extremely significantly compared with wild strain (P＜0.01).The mortality of ΔSodA,ΔTrxA and ΔTrxC strains were 10%,50% and 20%,respectively,and the tissue bacterial load was 3.6 lg CFU/g-4.4 lg CFU/g,4.2 lg CFU/g-5.1 lg CFU/g and 3.1 lg CFU/g-4.1 lg CFU/g,respectively.In the wild strain group,the mortality was 90%,and the tissue load was 6.4 lg CFU/g-7.8 lg CFU/g.The activities of superoxide dismutase (SOD),catalase (CAT) and total antioxidant capacity (T-AOC) in serum of mice infected with ΔSodA,ΔTrxC and ΔTrxA strains were extremely significantly higher than those of wild strain (P＜0.01).The activities of aspartate aminotransferase (AST),alanine aminotransferase (ALT) and alkaline phosphatase (ALP) were extremely significantly lower than those of wild strain (P＜0.01).【Conclusion】 SodA and TrxC genes of Streptococcus suis type 2 counteracted the damage caused by oxidative stress by neutralizing superoxide ions in bacteria and maintaining protein homeostasis,thus mediating bacterial virulence.TrxA might be a regulatory gene involved in antioxidant stress response.

Key words: Streptococcus suis type 2; anti-oxidative stress; SodA gene; TrxA gene; TrxC gene

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