Cations and oxidative stress response in Streptococcus pneumoniae

Streptococcus pneumoniae is a bacterium, which colonizes the human nasopharynx and can cause serious disease, such as pneumonia, otitis media, meningitis, and bacteremia. Generally, groups at risk for invasive pneumococcal disease are young children, elderly and immuno-compromised patients, both in developed and developing countries. Throughout the host, S. pneumoniae encounters various oxygen radicals, which can kill or damage the bacterium. The ability to withstand the damaging effects of oxygen radicals is crucial for the bacterial ability to cause disease. Our understanding of the pneumococcal defenses against oxidative stress is far from complete. In the present thesis, a novel protein complex is described, which protects the bacteria from the hazardous effects of oxygen radicals, most likely by repairing damaged proteins. Pneumococcal mutants lacking this complex were also less virulent in mouse models mimicking disease. Moreover, the presented results show for the first time that oxidative stress resistance is vital for the bacteria to survive on dry surfaces. This desiccation tolerance is thought to aid the transmission of the bacteria. Two key components necessary for the survival of desiccation stress are described in this thesis. Altogether, the present studies have provided further insights into (1) how S. pneumoniae copes with oxygen radicals and (2) the significance of oxidative stress resistance in infection and pathogenesis