COMPARISON OF OUTER-MEMBRANE PROTEINS OF PASTEURELLA-HAEMOLYTICA EXPRESSED IN-VITRO AND IN-VIVO IN CATTLE

Outer-membrane protein (OMP) profiles of two serotype Al isolates of P asteurella haemolytica were compared by SDS-PACE and Western blotting with bovine convalescent serum after growth (a) in vitro under iron-su fficient and -deficient conditions, (b) in vivo in the lungs of experi mentally infected calves and (c) in vivo in diffusion chambers implant ed into the peritoneal cavities of calves. Lung-grown bacteria differe d from iron-sufficient in vitro-grown bacteria in having enhanced expr ession of the previously recognized 71, 77 and 100 kDa iron-regulated proteins, reduced expression of 18, 31, 39.5 and 50 kDa proteins, and expression of a 19 kDa protein. Differences were also apparent in the Western blot profiles of OMPs of in vitro- and lung-grown bacteria. Th ese included the apparent lack of recognition of the 100 kDa protein i n the lung-grown bacteria, but not in the in vitro-grown bacteria, and more intense staining of a 47 kDa protein in in vitro-grown bacteria, but not in lung-grown bacteria. The OMP profiles of the chamber-grown bacteria resembled those of the lung-grown bacteria in that expressio n of the 18, 19, 31 and 39.5 kDa proteins was similar. These similarit ies demonstrated that the chamber-grown bacteria had adapted to the in vivo environment, and that growth conditions within the chambers rese mbled, but not perfectly, those within the lungs. For example, express ion of the three iron-regulated OMPs was very low in the chamber-grown bacteria compared to the lung-grown bacteria. The OMP profiles of bac teria grown in vitro in newborn calf serum closely resembled those of lung-grown bacteria, suggesting that in vivo growth may be partly repr oduced in vitro by growing the bacteria in newborn calf serum.