1 Section of Microbiology, Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK.
2 Department of Microbiology, Harvard Medical School, Boston, MA, USA.
3 Section of Microbiology, Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK. sophie_helaine@hms.harvard.edu.
4 Department of Microbiology, Harvard Medical School, Boston, MA, USA. sophie_helaine@hms.harvard.edu.