Construction of Δ0948 complementary strain of Streptococcus suis 2 and its effect on hemolysin secretion and virulence / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To construct Streptococcus suis type 2 Δ0948 complementary strain and verify its effect on suilysin (SLY) secretion and virulence. Methods:The SSU05_0948 gene sequence with promoter was amplified by PCR and ligated to pAT18 vector to construct complementary strain and verify its expression through Western blot. Growth curve was drawn to compare the growth of complementary strain against the wild-type strain and mutant strain in different periods. CD1 mice challenge model was used to verify whether complementary strain could restore the virulence of mutant. SLY hemolytic activity and Western blot were compared the effect of complementary strain and wild-type strain and mutant strain on SLY protein secretion at different time points.Results:The complementary strain was successfully constructed, but the expression of SSU05_0948 was lower than the wild-type strain. The growth rate of the complementary strain was significantly slower than the wild-type strain and mutant strain in the logarithmic growth phase, but the same in the platform phase. The CD1 mice challenge model showed the complementary strain could basically restore the virulence of the mutant strain. The hemolytic activity of SLY and Western blot showed that SSU05_0948 could inhibit the secretion of SLY protein in the early and middle logarithmic phase, but did not affect the secretion of SLY in the late logarithmic and platform phase, while the complementary strain could restore the secretion of SLY protein.Conclusions:The complementary strain CΔ0948 of Streptococcus suis can restore the virulence of mutant strain Δ0948, and SSU05_0948 affects the virulence of Δ0948, which provides a new idea for the prevention and treatment of Streptococcus suis.