Characterization of Putative Type IV Secretion System of Bacillus anthracis

Background: Bacillus anthracis causes anthrax disease in livestock and occasionally in humans mainly through three toxic proteins: protective antigen, lethal factor and edema factor. Synthesis of the toxic proteins in bacteria and its pathogenic role in the human host is well known. But, how these toxins are secreted from bacterium to the host or in the culture medium is not known. Methods: A group of researchers have shown (through in silico prediction) that several genes of B. anthracis have similarity with the genes which codes the subunit of the Type IV Secretion System (T4SS) known in other bacteria. In this study, we have tried to explore the existence of T4SS in B. anthracis using molecular biology tools. Result: As an initial lead, three genes (GBAA-pXO1-0064, GBAA-pXO1-0085VirB11 and Bas3783) of B. anthracis T4SS (out of more than 10) were cloned and expressed in E. coli. Among them, gene Bas3783 (VirD4 homolog) is genome encoded therefore; it is sequenced and further characterized for its DNA binding activity and oligomerization. Results obtained from this study indicated the existence of T4SS in B. anthracis.