Department of Genetics.|Applied Bioinformatics, Department of Computer Science, Quantitative Biology Center and Center for Bioinformatics, University of Tübingen, 72076 Tübingen, Germany.|Applied Bioinformatics, Department of Computer Science, Quantitative Biology Center and Center for Bioinformatics, University of Tübingen, 72076 Tübingen, Germany.|Department of Bacteriology and J. F. Crow Institute for the Study of Evolution, University of Wisconsin-Madison, Madison, WI 53706, USA.|Bioinformatics Group, Wageningen University, 6708PB Wageningen, The Netherlands.