Filipe, Sérgio RaposoHenriques, Mafalda Soeiro Xavier2014-04-172012-12http://hdl.handle.net/10362/11940Dissertation presented to obtain the Ph.D degree in Biology.The capsular polysaccharide (CPS), or capsule, is one of the main virulence factors of Streptococcus pneumoniae. This gram-positive bacterium can asymptomatically colonize the nasopharynx of healthy individuals, but it also has the capacity to spread to other parts of the host’s body and cause disease. The ability of pneumococcal bacteria to cause invasive disease is dependent upon the presence of the CPS, which surrounds the entire cell surface, protecting it from the host immune system.(...)engdoctoral thesis