Fabian Blombach1
, Kira S Makarova2
, Jeannette Marrero3
, Bettina Siebers3
, Eugene V Koonin2
and John van der Oost1 
1
Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands
2
National Center for Biotechnology Information, NLM, National Institutes of Health, Bethesda, Maryland 20894, USA
3
University Duisburg-Essen, Faculty of Chemistry, Biofilm Centre, Molecular Enzyme Technology and Biochemistry, Lotharstrasse, Duisburg, Germany