Microarray analysis of Streptococcus pneumoniae gene expression changes to human lung epithelial cells.

Streptococcus pneumoniae infection starts from the respiratory tract where interaction with host epithelial cells occurs. To gain more insights on pneumococcal pathogenesis, an oligonucleotide (oligo)-based microarray was used to investigate gene expression changes of one serotype 3 encapsulated pathogenic S. pneumoniae strain 82 and one unencapsulated avirulent S. pneumoniae strain R6 upon exposure to human lung epithelial cells (A549) for 1 and 3 h, respectively. We observed that genes associated with many functional categories were differentially regulated in strain 82, such as genes in pathogenesis, cell envelope, transcription, translation, transport, metabolism, and unknown functions. In contrast, few genes were changed in strain R6 except for genes in ribonucleotide biosynthesis and unknown functions. Quantitative real-time PCR analysis confirmed the microarray results for most of the genes tested. To further characterize functions of the selected genes, knockout mutants were constructed in strain R6. We demonstrated that 2 genetic loci, SP_2170 (AdcB, zinc ABC transporter) and SP_0157 (hypothetical protein), were involved in adherence to A549 cells. These data suggest that divergent gene expression changes occur in S. pneumoniae pathogenic and avirulent strains during interaction with human lung epithelial cells. Some of those genes are involved in pneumococcal pathogenesis.