1. Department of Microbiology and Biotechnology, University of Hamburg , Ohnhorststr. 18, 22609 Hamburg, Germany
2. Microbiology cluster, RIBES, Radboud University , Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands
3. Department of Food Microbiology and Hygiene, University of Bonn , Friedrich-Hirzebruch-Allee 7, 53115 Bonn, Germany