Capsule visualization in CAF10 and its various S-layer gene deletion derivatives. (A) CAF10 (EA1+ Sap+). (B) CBA91 (EA1+). (C) CSM91 (Sap+). (D) CSM11. Thin sections of cultures grown in capsule synthesis-inducing conditions were treated during fixation and embedding to highlight the peptidoglycan (p), the S-layer (s), and the fibrillar capsule (c) (see Materials and Methods). The cytoplasmic membrane is also indicated (m). The cell surface components (p, s, c, and m) are indicated in panel A. Note that the S-layer is absent from the bacterium in panel D. Bar, 250 nm.