Center for Biofilm Engineering and Department of Microbiology, Montana State University Bozeman, Bozeman, Montana 59717-3980, , USA1
Department of Chemical Engineering, Montana State University Bozeman, Bozeman, Montana 59717-3980, , USA2
For correspondence. Philip S. Stewart. Tel: +1 406 994 2890. Fax: +1 406 994 6098. e-mail: phil_s{at}erc.montana.edu