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Morphogenesis of Bacillus Spore Surfaces. Venkata G. R. Chada, 2003.Spores produced by bacilli are encased in a proteinaceous multilayered coat and, in some species (including Bacillus anthracis), further surrounded by a glycoprotein-containing exosporium . To characterize bacillus spore surface morphology and to identify proteins that direct formation of coat surface features, we used atomic-force microscopy (AFM) to image the surfaces of wild-type and mutant spores of Bacillus subtilis, as well as the spore surfaces of Bacillus cereus 569 and the Sterne strain of Bacillus anthracis . This analysis revealed that the coat surfaces in these strains are populated by a series of bumps ranging between 7 and 40 nm in diameter, depending on the species . Furthermore, a series of ridges encircled the spore, most of which were oriented along the long axis of the spore . The structures of these ridges differ sufficiently between species to permit species-specific identification . We propose that ridges are formed early in spore formation, when the spore volume likely decreases, and that when the spore swells during germination the ridges unfold . AFM analysis of a set of B . subtilis coat protein gene mutants revealed three coat proteins with roles in coat surface morphology: CotA, CotB, and CotE . Our data indicate novel roles for CotA and CotB in ridge pattern formation . Taken together, these results are consistent with the view that the coat is not inert . Rather, the coat is a dynamic structure that accommodates changes in spore volume .
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