Identification of Streptococcus pneumoniae genes specifically induced in mouse lung tissues

Abstract

To identify Streptococcus pneumoniae genes expressed specifically during infections, a selection system based on the in vivo expression technology (IVET) was established. galU, which is critical for capsular polysaccharide biosynthesis, and lacZY encoding beta-galactosidase were employed as dual reporter genes to screen in-vivo-induced (ivi) genes of S. pneumoniae. The galU-deficient mutant of S. pneumoniae is incapable of utilizing galactose, thus failing to synthesize capsular polysaccharide, and therefore loses its ability to survive in the host. A promoter-trap library was constructed in S. pneumoniae, which was used to infect BALB/c mice in an intranostril model. Those strains recovered from lung tissue of mice and exhibiting a white colony phenotype on tryptic soy agar containing X-gal (5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside) were collected and identificated. A total of 15 unique sequences were obtained through in vivo screening. The ivi genes of S. pneumoniae are involved in many processes, such as colonization and adherence, energy metabolism, nutrient substance transport, transcription regulation, DNA metabolism, and cell wall synthesis. There are some hypothetical proteins whose functions are not clear. This novel IVET is a useful tool for identifying ivi genes in S. pneumoniae.

A Novel Protein, RafX, Is Important for Common Cell Wall Polysaccharide Biosynthesis in Streptococcus pneumoniae: Implications for Bacterial Virulence

“…rafX (accession no. AE007480) was identified as an in vivo-inducible gene in a model of murine pneumonia and sepsis in our laboratory (38). rafX is part of the raf operon with five upstream genes that have been shown to be involved in raffinose metabolism; nevertheless, the role of the RafX protein has not been elucidated (39).…”

Streptococcus pneumoniae Can Utilize Multiple Sources of Hyaluronic Acid for Growth

“…A previous report demonstrated that expression of the operon containing ugl and spr0293 to spr0295 is upregulated during infection of the lung, indicating that utilization of hyaluronic acid may also contribute to bacterial growth during disease (33). It has been suggested that the pneumococcal hyaluronate lyase aids bacterial invasion, and it is possible that localized invasion contributes to bacterial colonization in addition to degrading hyaluronic acid for nutrition (22,47).…”

Identification of a novel pneumococcal vaccine antigen preferentially expressed during meningitis in mice

“…Several strategies have been employed to screen in vivo-induced genes, including in vivo expression technology (IVET) (12), signature-tagged mutagenesis (STM) (13,14), differential fluorescence induction (DFI) (15)(16)(17), DNA microarray (18,19), reverse vaccinology (20,21), antigenome technology (22,23), and genomic array footprinting (GAF) (24). The availability of complete pathogen genome sequences has stimulated the development and wide-spread application of DNA arrays, which has revolutionized the study of genes that are involved in microbial pathogenesis (25).…”