- T Koga: Department of Food Microbiology, Tokushima University School of Medicine, Japan.
Two polymyxin-resistant isolates V2PXR and P1R4PXR of Vibrio parahaemolyticus were spontaneously isolated and compared with the polymyxin-sensitive strains as to their chemical compositions of cell envelopes and their outer membrane protein compositions. When grown in the presence or absence of polymyxin, the cell envelopes of polymyxin-resistant isolates showed a significantly increased content of protein as compared with those of respective polymyxin-sensitive strains. Both polymyxin-resistant isolates produced the major outer membrane protein b' after growth in the presence or absence of polymyxin. A new major outer membrane protein with an apparent molecular weight of 26,000 (26 K protein) was produced by polymyxin-resistant isolates grown in the presence of polymyxin. The production of 26 K protein was also observed in the polymyxin-resistant isolates grown in the medium containing low concentrations of NaCl (0.2% and 0.5%).