The pmrF polymyxin-resistance operon of Yersinia pseudotuberculosis is upregulated by the Pho-P-PhoQ two-component system but not by PmrA-PmrB, and is not required for virulence. - Marceau, M.; Sebbane, F.; Ewann, F.; Collyn, F.; Lindner, B.; Campos, M. A.; Bengoechea, J.-A.; Simonet, M. (Microbiology (13500872), 2004)