A collagen-like surface glycoprotein is a structural component of the Bacillus anthracis exosporium

Mol Microbiol. 2002 Jul;45(1):169-78. doi: 10.1046/j.1365-2958.2000.03000.x.


Bacillus anthracis, the aetiological agent of anthrax, is a Gram-positive spore-forming bacterium. The exosporium is the outermost integument surrounding the mature spore. Here, we describe the purification and the characterization of an immunodominant protein of the spore surface. This protein was abundant, glycosylated and part of the exosporium. The amino-terminal sequence was determined and the corresponding gene was identified. It encodes a protein of 382 amino acid residues, the central part of which contains a region of GXX motifs presenting similarity to mammalian collagen proteins. Thus, this collagen-like surface protein was named BclA (for Bacillus collagen-like protein of anthracis). BclA was absent from vegetative cells; it was detected only in spores and sporulating cells. A potential promoter, dependent on the sigma factor sigma(K), which is required for a variety of events late in sporulation, was found upstream from the bclA gene. A bclA deletion mutant was constructed and analysed. Electron microscopy studies showed that BclA is a structural component of the filaments covering the outer layer of the exosporium.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Anthrax / microbiology
  • Anthrax / mortality
  • Bacillus anthracis / chemistry*
  • Bacillus anthracis / metabolism
  • Bacillus anthracis / pathogenicity
  • Bacillus anthracis / ultrastructure
  • Bacterial Proteins* / genetics
  • Bacterial Proteins* / isolation & purification
  • Bacterial Proteins* / metabolism
  • Base Sequence
  • Female
  • Genes, Bacterial / genetics
  • Membrane Glycoproteins* / chemistry
  • Membrane Glycoproteins* / genetics
  • Membrane Glycoproteins* / isolation & purification
  • Membrane Glycoproteins* / metabolism
  • Mice
  • Microscopy, Electron
  • Molecular Sequence Data
  • Sequence Analysis, DNA
  • Spores, Bacterial / chemistry*
  • Spores, Bacterial / ultrastructure
  • Virulence


  • Bacterial Proteins
  • BclA protein, Bacillus anthracis
  • Membrane Glycoproteins