1. Departmento de Biología Molecular; Facultad de Veterinaria; Universidad de León; León Spain
2. Department of Microbiology and Immunology; Life Sciences Institute; University of British Columbia; Vancouver V6T 1Z3 Canada
3. Department of Biochemistry and Molecular Biology; Life Sciences Institute; University of British Columbia; Vancouver V6T 1Z3 Canada
4. Institute of Molecular Microbiology and Biotechnology; University of Münster; Münster Germany