Streptococcus pneumoniae is an important human pathogen capable of causing several diseases including bacterial meningitis and pneumonia. However, it more often harmlessly colonizes the human nasopharynx, sharing its niche with bacteria of other species in the microbiota. We are investigating communication between bacterial species in this environment which is mediated by peptides whose sequences are found in bacterial ribosome-associated proteins.
To cause disease, the bacteria must invade the body and are aided in this by their polysaccharide capsule, a major virulence factor that confers protection against opsonophagocytosis. The more than 100 known biochemical varieties of capsule are used to classify pneumococci by serotype. Disease severity is affected by serotype and we are researching the mechanisms for this.