Newly identification of virulence plasmid-encoded factor(s) secreted by Bacillus anthracis

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Anthrax is an infectious disease caused by gram-positive bacteria, Bacillus anthracis. The most important virulence-related proteins : the virulence factors (PA, EF & LF) and the capsule synthesis factors (CapBCADE) are encoded by two large unique plasmids.First, we analyzed two large plasmid pXO1 (180kb) and pXO2 (95kb) in silico, we found several short ORFs with secretion signal sequence. Then, we found 23 of 204 ORFs form pXO1, and 12 of 104 ORFs from pXO2. Although signal peptidase I (SPI) is encoded by chromosome, it is especially interested that newly SPI-like protein is also encoded by pXO2.To test the putative secreted factors, culture supernatant of various strains, WT [pXO1+pXO2+], pXO2-depleted [pXO1+], pXO1-depleted [pXO2+], and both plasmids-depleted B.anthracis, were added to several cultured cells. As a result, we observed morphology change of HeLa and vero cell only treated by the culture supernatants of WT and pXO1+ strains. This morphology change of cultured cell might be attributed to pXO1. Then we tried to confirm the possibility of various cellular responses including apoptosis and actin-polymerization.