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• Michael Koomey
• Erling Seeberg
• Anne Brit Kolstø
• Tone Tønjum
• L. Sigve Håvarstein
• Kirsten Skarstad

Presently, human infections caused by S. pneumoniae (the pneumococcus) are becoming increasingly difficult to treat, predominantly due to the emergence of antibiotic resistant strains. High-level penicillin resistant pneumococci are reported with increasing frequency, and now constitute a substantial proportion of all clinical isolates found in many countries. We have previously shown that natural competence in S. pneumoniae is regulated by a cell-cell signalling mechanism mediated by a peptide-inducible two- component system [1,2,3]. One of our main goals is to study the nature of the regulatory networks that these two-component systems direct. In this context, we are currently developing technologies to study both protein-DNA interactions and protein-protein interactions. Using surface plasmon resonance equipment, mass spectrometry, array-based transcription profiling, as well as the classical methods of molecular biology, we aim to unravel fundamental aspects of the development of natural competence, antibiotic resistance, and virulence in S. pneumoniae

• 1. Håvarstein LS, Coomaraswamy G, Morrison DA (1995) An unmodified heptadecapeptide pheromone induces competence for genetic transformation in Streptococcus pneumoniae.Proc Natl Acad Sci U S A. 92: 11140-4.
• 2. Håvarstein LS (1998) Identification of a competence regulon in Streptococcus pneumoniae by genomic analysis. Trends Microbiol. 6: 297-9.
• 3. Steinmoen H, Knutsen E, Håvarstein LS. (2002) Induction of natural competence in Streptococcus pneumoniae triggers lysis and DNA release from a subfraction of the cell population. Proc Natl Acad Sci U S A. 99: 7681-6.

Gram-stained cells of Streptococcus pneumoniae.

Pneumococci reside in biofilms on the mucous membranes of the oral cavity and nasopharynx. They are able to communicate with each other by secreting strain specific peptide pheromones. This communication system is used to monitor the density of the strain population, and when a critical number of cells are present they decide to exchange DNA. A subfraction of the cells lyse and release DNA (the donors), whereas the majority of the cells (the recipients) become competent for natural transformation and take up the DNA released by the donors.