1. Development of new tools to study the cell biology and origins of phenotypic variation in the human pathogen Streptococcus pneumoniae: An overview of recently started projects and future directions Jan-Willem Veening Molecular Genetics Department j.w.veening@rug.nl http://molgen.biol.rug.nl

2. Human pathogen Causes e.g. pneumoniae, otitis media, septicaemia, meningitis Every year >10 6 deaths worldwide Transient commensal in ~40% of human population Resides in nasopharynx >90 different capsule types Capsule-polysaccharide vaccination Vaccine against 23 serotypes Treatment with antibiotics Why study Streptococcus pneumoniae?

3. Displacement of vaccine serotypes by other serotypes Invasive disease caused by non-vaccine serotypes Increased antibiotic resistance threats: Why study Streptococcus pneumoniae?

4. Development of protein vaccines and new antimicrobials Need for protein targets that are essential and common in most strains But… cell biology is poorly understood future: Why study Streptococcus pneumoniae?

5. S. pneumoniae needs a complex regulatory network to regulate host-pathogen interactions –Makes a switch from commensal to pathogen –A common mechanism to elude stresses such as antibiotic stress, immune response stress or to invade the host is by cellular differentiation of a fraction of the clonal population. This heterogeneity can originate from noise that arises during the process of transcription Phenotypic variation! Mechanisms poorly understood Compact genome of about 2 MB –only two sigma factors Genetically accessible –Naturally competent for transformation –Use of linear DNA (e.g. PCR products) Single cell analysis toolbox starting to become available