Clostridium difficile exosporium cysteine-rich proteins are essential for the morphogenesis of the exosporium layer, spore resistance, and affect C. difficile pathogenesis
Fig 2
Transmission electron micrographs of C. difficile cdeM and cdeC spores.
(A) Thin sections of C. difficile wild-type, cdeC and cdeM spores were analyzed by transmission electron microscopy as described in the Method section. Representative micrographs of several C. difficile wild-type, cdeC and cdeM spores are shown in the upper panel. Selected individual spores of wild-type with thick and thin exosporium layer are shown. The middle panel shows representative individual spores of the mutant strains cdeC and cdeM. The lower panel shows a magnified view of the thin section of wild-type, cdeC and cdeM spores with thick and thin exosporium layers. Ex, exosporium; Ic, inner coat; Ec, external coat; Cx, cortex. (B) The thickness of the exosporium and outer and inner coat layers of C. difficile wild-type (white bars), cdeC (gray bars) and cdeM (black bars) strains were analyzed by transmission electron microscopy of at least 10 individual spores with an apparent thick-exosporium morphotype. Error bars denote standard errors of the means. Asterisks (*) denote statistical difference at P < 0.05 and (**) denote statistical difference at P < 0.001 respect to wild-type. Scale bars are shown in each figure: the bars in the upper panels represent 1 nm, middle panel 100 nm and the bars in the lower panels represent 200 nm. (C) The surface accessibility of CdeC on C. difficile 630erm wild-type and cdeC mutant spores was analyzed by immunofluorescence with rat anti-CdeC serum as described in Methods section. (D) The surface accessibility of CdeM on C. difficile 630erm wild-type and cdeM mutant spores was analyzed by immunofluorescence with rabbit anti-CdeM spores as described in Methods section.