Institute of Microbiology, ETH Zurich, Zürich, Switzerland. misselwitz@micro.biol.ethz.ch|Institute of Microbiology, ETH Zurich, Zürich, Switzerland. misselwitz@micro.biol.ethz.ch|Institute of Microbiology, ETH Zurich, Zürich, Switzerland. misselwitz@micro.biol.ethz.ch|Institute of Microbiology, ETH Zurich, Zürich, Switzerland. misselwitz@micro.biol.ethz.ch|Institute of Microbiology, ETH Zurich, Zürich, Switzerland. misselwitz@micro.biol.ethz.ch|Institute of Microbiology, ETH Zurich, Zürich, Switzerland. misselwitz@micro.biol.ethz.ch|Institute of Microbiology, ETH Zurich, Zürich, Switzerland. misselwitz@micro.biol.ethz.ch|Institute of Microbiology, ETH Zurich, Zürich, Switzerland. misselwitz@micro.biol.ethz.ch