To investigate the biological function of pnp gene of Streptococcus suis serotype 2,the pnp gene deletion mutant△pnp and complementary strain C△pnp of S.suis serotype 2 strain 05ZYH33 were constructed using markerless genetic manipulation technique,and the growth curve,bacterial morphological structure,biofilm formation ability,hemolysis,antimicrobial susceptibility,oxidative resistance and acid tolerance were detected to evaluate the biological function of the gene.The results showed that the △pnp mutant and C△pnp strain were successfully constructed.The OD600nmvalues of 05ZYH33,△pnp and C△pnp were measured after culture at different temperatures,and the growth curves were plotted.The morphological structure of each strain was observed by transmission electron microscopy after Gram staining.The biofilm formation ability of each strain was detected by titration micropore plate method.The hemolysis characteristics of each strain were analyzed by contact method.The strains were cultured on THB plates containing different antibiotics,and the antimicrobial sensitivity was analyzed.The strains were cultured under oxidative and acidic conditions,and their oxidative tolerance and acid tolerance were evaluated by detecting the survival rate.The growth curve of each strain showed that the growth rate of △pnp was significantly lower than that of the wild strain and C△pnp,and the survival ability of △pnp decreased under cold stress.The results of morphological structure and hemolytic test of each strain showed that the cell wall peptidoglycan layer structure of the deletion strain △pnp was looser and the hemolytic ability decreased.The results of antimicrobial sensitivity test showed that the sensitivity of △pnp to many different types of antibiotics was enhanced.The results of oxidative tolerance and acid tolerance test showed that the antioxidant and acid resistance of the deletion strain △pnp decreased.The above results demonstrated that pnp gene is an important regulator of S.suis serotype 2,which is involved in regulating the adaptability of bacteria to changes in the external environment.This study lays a foundation for scientific prevention and control of swine streptococcosis and development of new antibacterial agents.
Streptococcus suis serotype 2pnp genegene deletionbiological function
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