| description |
We performed a genome-wide analysis by using a next generation sequencer to investigate the effect of pulmonary surfactant on gene expression in Staphylococcus aureus, a clinically important opportunistic pathogen. The RNA-seq analysis of bacterial transcripts at late log phase revealed 142 genes up regulated more than 2-fold by addition of the pulmonary surfactant to the culture medium. Among them, we confirmed by quantitative RT-PCR analysis that mRNA amounts of genes encoding ESAT-6 secretion system C (EssC), an unknown hypothetical protein NWMN_0246 (pulmonary surfactant-inducible factor A; PsiA), and hemolysin gamma subunit B (HlgB) increased by 3 to 10-fold by the surfactant treatment. Among the major constituents of pulmonary surfactant, phospholipids did not stimulate the expression of the 3 genes, whereas palmitic acid, the most abundant fatty acids in the pulmonary surfactant and also known as an antibacterial substance, did. Moreover, the induction of these genes was also observed by supplying the culture with detergents. The induction of gene expressions by surfactant or palmitic acid was not observed in a disruption mutant of the sigB gene that encodes an alternative sigma factor involved in bacterial stress responses. Furthermore, each disruption mutant of the essC, psiA, or hlgB gene showed attenuated ability of survival in the lung and of host killing in a murine pneumonia model. These results suggest that S. aureus resists against membrane stresses caused by free fatty acids present in the pulmonary surfactant through regulation of virulence gene expression that contributes to pathogenesis within lungs of host animals. |