Construction and Function Study of the neuB Gene Encoding Sialic Acid Synthase Knock-out Mutant of Streptococcus suis Serotype 2

Abstract:

Based on the principle of homologous recombination, we construct gene knock-out mutant of neuB gene encoding sialic acid synthase in Streptococcus suis serotype 2 (SS2) virulent strain 05ZYH33. PCR analysis and Southern hybridization confirmed that the coding gene of neuB was replaced completely by spcr cassette in one mutant, the mutant of 05ZYH33 neuB gene was successfully constructed. Analysis of biological characteristics showed that there were no differences in mycelial morphology, hemolytic activity and dyeing properties between the mutant and 05ZYH33; but the capsule of mutant was thinner and more compacted than that of the wild type strain 05ZYH33. Virulence assays with murine model confirmed that the mutant is avirulent. These observations indicate that sialic acid plays an important role in the pathogenesis and invasiveness of SS2.

Key words:Streptococcus suis serotype 2, Sialic acid synthase, Gene knock-out, Biological characteristics, Virulence assays