Fig 8.

Deep breaks in the macrocolony surfaces of strains that produce curli but not cellulose generate concentric ring morphology. (A) Top-view image of a mature W3110 macrocolony grown at 28°C on a CR plate showing the curli-dependent ring pattern. (B) Fluorescence image at low magnification of a cross-section through a W3110 macrocolony grown in the presence of TS. (C) Enlarged top-view image of W3110 macrocolony rings. The arrow indicates naturally occurring breaks at the top of the rings. (D, E, and F) SEM images showing changes at the W3110 macrocolony surface over the course of ring formation. The arrow in panel F indicates bacteria colonizing the crevice at late time points. (G) SEM image of the colony surface (at ×24,000 magnification) showing the initial bacterial colonizers of a crevice (day 6, ff., in panel F), which are rod-shaped and carry flagella. (H) SEM image (at ×12,000 magnification) showing bacteria later during the colonization of a crevice (day 7, ff.), which have almost filled the crevice, have become shorter and in part have started to generate curli around their cell bodies. (I, J, and K) SEM images showing microbreaks at the top of a mature W3110 macrocolony (at ×6,000, ×12,000, and ×24,000 magnifications, respectively).