Cell-to-cell communication across the prokaryote-eukaryote boundary.

Plymouth Marine Laboratory, Prospect Place, Plymouth, PL1 3DH, UK. School of Biosciences, University of Birmingham, Birmingham, B15 2TT, UK, Department of Molecular Biology, Umeå University, S-901 87 Umeå, Sweden, School of Pharmaceutical Sciences, University of Nottingham, Nottingham, NG7 2RD, UK and Institute of Infections and Immunity, University of Nottingham, Queen’s Medical Centre, Nottingham NG7 2UH, UK. † To whom correspondence should be addressed. E-mail [email protected]