1 Institut Pasteur, Biology and Genetics of the Bacterial Cell Wall Unit, 28 rue du Dr. Roux, 75724 Paris Cedex 15, France; INSERM, Avenir Group, Paris, France.
2 Institut Pasteur, Biology and Genetics of the Bacterial Cell Wall Unit, 28 rue du Dr. Roux, 75724 Paris Cedex 15, France; INSERM, Avenir Group, Paris, France. Electronic address: [email protected].
3 McMaster University, Hamilton, Canada.
4 Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK.