RESUMO
OBJECTIVE: To study the biological character and pathogenic effect of a lysozyme-like protein in Streptococcus pneumoniae. METHODS: The gene knockout mutant was constructed by the long flanking homology polymerase chain reaction. The mutant containing rescue plasmid to complement the lysozyme-like gene was also constructed. The differences in biology and pathogenicity in D39 wild strain, gene knockout mutant and gene knockout mutant containing rescue plasmid were observed to identify the functions of the lysozyme-like gene. RESULTS: Compared with the wild strain, the gene knockout mutant had the characteristics of slower growth, declining virulence, and obviously reduced capsule polysaccharide synthesis. Complement experiment showed when the rescue plasmid was transformed into the mutant strain, the mRNA level of hypothetical lysozyme-like gene in the gene knockout mutant containing rescue plasmid was higher than that of the wild strain. Although the levels of virulence and capsule polysaccharide synthesis could be partly complemented compared with those of the gene knockout mutant, but not reached the levels in the wild strain. CONCLUSIONS: The lysozyme-like protein, a new Streptococcus pneumoniae virulence factor, may regulate the proliferation and the capsular polysaccharides synthesis of Streptococcus pneumoniae to affect expression of virulence.
