Center of Biotechnology, Bielefeld University, Postfach 10 01 31, 33501 Bielefeld, Germany. jherold@cebitec.uni-bielefeld.de|Center of Biotechnology, Bielefeld University, Postfach 10 01 31, 33501 Bielefeld, Germany. jherold@cebitec.uni-bielefeld.de|Center of Biotechnology, Bielefeld University, Postfach 10 01 31, 33501 Bielefeld, Germany. jherold@cebitec.uni-bielefeld.de