Contribution of ExsFA and ExsFB proteins to the localization of BclA on the spore surface and to the stability of the bacillus anthracis exosporium.
Spores of Bacillus anthracis, the etiological agent of anthrax, and the closely related species Bacillus cereus and Bacillus thuringiensis, possess an exosporium, which is the outermost structure surrounding the mature spore. It consists of a paracrystalline basal layer and a hair-like outer layer. To date, the structural contribution of only one exosporium component, the collagen-like glycoprotein BclA, has been described. It is the structural component of the hair-like filaments. Here, we describe two other proteins, ExsFA and ExsFB, which are probably organized in multimeric complexes with other exosporium components, including BclA. Single and double exsF deletion mutants were constructed and analyzed. We found that inactivation of exsF genes affects the BclA content of spores. BclA is produced by all mutants. However, it is partially and totally released after mother cell lysis of the DeltaexsFA and DeltaexsFA DeltaexsFB mutant strains, respectively. Electron microscopy revealed that the exsF mutant spores have defective exosporia. The DeltaexsFA and DeltaexsFA DeltaexsFB spore surfaces are partially and totally devoid of filaments, respectively. Moreover, for all mutants, the crystalline basal layer appeared unstable. This instability revealed the presence of two distinct crystalline arrays that are sloughed off from the spore surface. These results indicate that ExsF proteins are required for the proper localization of BclA on the spore surface and for the stability of the exosporium crystalline layers.
Sylvestre
Patricia
P
Unité Toxine et Pathogénie Bactériennes, Institut Pasteur, 28 rue du Dr Roux, 75724 Paris cédex 15, France.
Couture-Tosi
Evelyne
E
Mock
Michèle
M
D001408:Bacillus anthracis / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D013171:Spores, Bacterial / Q000737:chemistry / Q000648:ultrastructure
D001426:Bacterial Proteins; C470593:BclA protein, Bacillus anthracis; D008562:Membrane Glycoproteins