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The pneumococcal response to oxidative stress includes a role for Rgg

¹ University of Leicester;
² University of London

Streptococcus pneumoniae resides in the oxygen-rich environment of the upper respiratory tract, and therefore the ability to survive in the presence of oxygen is an important aspect of its in vivo survival. To investigate how S. pneumoniae adapts to oxygen, we determined the global gene expression profile of the microorganism in aerobiosis and anaerobiosis. It was found that exposure to aerobiosis elevated the expression of 54 genes, while the expression of 15 genes was down-regulated. Notably there were significant changes in putative genome plasticity and hypothetical genes. In addition, increased expression of rgg, a putative transcriptional regulator, was detected. To test Rgg's role in the pneumococcal oxidative stress response, an isogenic mutant was constructed. It was found that the mutant was sensitive to oxygen and paraquat, but not to H2O2. In addition, the absence of Rgg strongly reduced biofilm forming ability of an unencapsulated pneumococcus. Virulence studies showed that the median survival time of mice infected intranasally with the rgg mutant was significantly longer than in the wild-type infected group, and the animals infected with the mutant developed septicaemia later than those infected intranasally with the wild type.

³ E-mail: hy3{at}le.ac.uk