1. Department of Biosciences and Nutrition; Karolinska Institutet; Huddinge; SE-171 77; Sweden
2. de Duve Institute; Université catholique de Louvain; Brussels; 1200; Belgium
3. Department of Molecular Biology; Area of Microbiology; University of León; León; 24006; Spain
4. Department of Biology; California State University; Fresno; CA; 93740; USA