Outer-membrane protein (OMP) profiles of two serotype A1 isolates of were compared by SDS-PAGE and Western blotting with bovine convalescent serum after growth (a) under iron-sufficient and -deficient conditions, (b) in the lungs of experimentally infected calves and (c) in diffusion chambers implanted into the peritoneal cavities of calves. Lung-grown bacteria differed from iron-sufficient -grown bacteria in having enhanced expression 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 - and lung-grown bacteria. These included the apparent lack of recognition of the 100 kDa protein in the lung-grown bacteria, but not in the -grown bacteria, and more intense staining of a 47 kDa protein in -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 expression of the 18, 19, 31 and 39.5 kDa proteins was similar. These similarities demonstrated that the chamber-grown bacteria had adapted to the environment, and that growth conditions within the chambers resembled, but not perfectly, those within the lungs. For example, expression of the three iron-regulated OMPs was very low in the chamber-grown bacteria compared to the lung-grown bacteria. The OMP profiles of bacteria grown in newborn calf serum closely resembled those of lung-grown bacteria, suggesting that growth may be partly reproduced by growing the bacteria in newborn calf serum.


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