1. New England Biolabs, Ipswich, Massachusetts, USA
2. Molecular and Cellular Biochemistry Department and Biology Department, Indiana University, Bloomington, Indiana, USA
3. Biomedical Sciences Research Complex, University of St Andrews, Fife, United Kingdom
4. Institut Pasteur, Unité Biologie Moléculaire du Gène chez les Extrêmophiles, Département de Microbiologie, Paris, France