Figure 6: The propensity of rodlins to form amyloid fibrils correlates with the presence of rodlets.

The outer surface of spores of the wild-type strain (A) is characterized by the rodlet layer. In contrast, no rodlets are detected on the surface of spores of the ∆rdlB strain (B). Introduction of the wild-type rdlB gene (contained on plasmid pIJ8630-rdlB) in the ∆rdlB strain restored rodlet formation (C). No complementation is observed when pIJ8630-∆17-42rdlB (D) or pIJ8630-rdlB− (E) are introduced in the ∆rdlB mutant strain. (F) Rodlets are also formed by the introduction of plasmid pIJ8630-rdlA*2 in the ∆rdlAB mutant. (G) Spore chains of the S. coelicolor wild-type strain as observed with scanning electron microscopy without platinum plasma coating. A transparent sheath-like structure is visible surrounding the separating spores. (H) Proposed model for the developmental transition of S. coelicolor aerial hyphae into chains of spores, which are enveloped by two amyloidal layers containing assembled chaplins (blue/purple) and rodlins (orange/green). Note that the rodlins are part of the outermost layer. The scale bar represents 100 nm (A–F) or 1 μm (G).