ANNA M. GRUDNIAK*, JOLANTA WŁODKOWSKA and KRYSTYNA I. WOLSKA Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Poland *Corresponding author: A. M. Grudniak, Institute of Microbiology, University of Warsaw, Warsaw, Poland; e-mail: grudam@biol.uw.edu.pl Submitted 11 February 2015,  Revised 16 July 2015, Accepted 17 July 2015...