Fig. 1.

Colony morphology of Bp strains on selective/differential media. a The growth of Bp strain MSHR668 on SBA plates illustrates the colony morphology variation that is commonly observed for Bp. On this plate, three colony types are shown: the majority of the colonies are small, round, and smooth (#1); the next most numerous are larger, shinier, and less opaque, and have a translucent edge (#2); and there are two “water splat” colonies that are large, flat, and translucent/clear, and have an irregular edge (#3). The growth of Bp strain K96243 illustrates morphologies produced by Bp on several selective media (b–e). b OFPBL plate. c AA plate showing a common colony morphology of Bp strains. d BCA plate. Strains metabolizing the peptones and pyruvate produce alkaline conditions changing the agar indicator color from orange to pink. e BCSA plate, used for Bp only. This medium distinguishes strains which metabolize the peptones (alkaline color change) or catabolize the carbohydrates (acidic color change from deep pink to yellow, as shown for K96243)