The spores of Bacillus cereus group (B. cereus, anthracis and thuringiensis) are surrounded by a paracristalline flexible yet resistant layer called exosporium that plays a major role in spore adhesion and virulence. The major constituent of its hair-like surface, the trimerized glycoprotein BclA, is attached to the basal layer through an N-terminal domain. It is then followed by a repetitive collagen-like neck bearing a globular head (C-terminal domain) that promotes glycoprotein trimerization. The collagen-like region of B. anthracis is known to be densely substituted by unusual O-glycans that may be used for developing species-specific diagnostics of B. anthracis spores and thus, targeted therapeutic interventions. In the present study, we have explored the species- and domain-specificity of BclA glycosylation within the B. cereus group. First, we have established that the collagen-like region of both B. anthracis and B. cereus are similarly substituted by short O-glycans that bear the species-specific deoxyhexose residues Anthrose and the newly-observed Cereose, respectively. Then, we have discovered that the C-terminal globular domains of BclA from both species are substituted by polysaccharide-like O-linked glycans, whose structures are also species-specific. The presence of large carbohydrate polymers covering the surface of Bacillus spores may have a profound impact on the way that spores regulate their interactions with biotic and abiotic surfaces and represents potential new diagnostic targets.
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