1. Centre for Microbiology and Virology, Polish Academy of Sciences, Lodowa 106, 93-232 Ldz, Poland
2. Department of Genetics of Microorganisms, University of Ldz, Banacha 12/16, 93237 Ldz, Poland
3. Molecular Microbiology Group, School of Biological Sciences, University of Surrey, Guildford GU2 5XH, UK