1. Department of Microbial, Biochemical and Food Biotechnology, University of the Free State, Nelson Mandela Drive, P.O. Box 339, Bloemfontein, Free State 9301, South Africa.
2. Centre for Confocal and Electron Microscopy, University of the Free State, Nelson Mandela Drive, P.O. Box 339, Bloemfontein, Free State 9301, South Africa.