FIG. 4.

Buoyant density profiles of S. iniae wild-type strains 9117 and 9066 and putative 9117 capsule mutants. A. Chart showing specific buoyant densities of wild-type and STM mutants in a Percoll gradient with endpoints of 1.03 to 1.13 mg/liter. Individual strains were added to the top of a gradient and centrifuged, facilitating separation to a specific density, which correlates to the amount of capsule expression. Strains with ample encapsulation have low buoyant density and will form bands in the lower concentration of the gradient, while strains with little or no encapsulation have high buoyant density and will separate out at a higher density. B. Photomicrographs of wild-type (WT) strain 9117 and putative capsule mutants illustrating the different chain lengths. Magnification, ×1,000.