Effect of the Lower Molecular Capsule Released from the Cell Surface ofBacillus anthracison the Pathogenesis of Anthrax

Abstract

Bacillus anthracis enters the body as an endospore, and encapsulation and toxin production occur after germination. Capsule is proposed to be an antiphagocytic factor, and toxin induces cytokine production for systemic shock. The dep gene, adjacent to the cap region for the encapsulation, degrades the high-molecular weight capsule (H-capsule) to the lower-molecular weight capsule (L-capsule), which releases into the culture supernatant. This study analyzed the biological function of the cap-dep region. The dep null mutant Sm-1, which formed H-capsule but not L-capsule, was avirulent. However, Sm-1 with an intact dep gene or with purified L-capsule recovered its pathogenicity. Sm-1 was subjected to phagocytosis by macrophages more easily than its parent strain, Sm, in vitro; in vivo, it cleared without L-capsule and grew well with L-capsule, which suggests that L-capsule is essential for in vivo multiplication. Moreover, a new name, capD, might be appropriate, because of the part of the cap operon involved in both polymerization and depolymerization of the capsule.

Poly-γ-Glutamate Capsule-Degrading Enzyme Treatment Enhances Phagocytosis and Killing of EncapsulatedBacillus anthracis

“…Gamma glutamyltranspeptidase, encoded by capD, has been functionally characterized as a virulence factor (4, 31, 52). The 55-kDa protein has depolymerase activity and degrades highmolecular-weight capsule with the release of small amounts of lower-molecular-weight species that have been suggested to contribute to virulence (31). CapD was also reported to be necessary for anchoring the capsule to the peptidoglycan (4).…”

“…The B. anthracis capsule depolymerase gene, capD, encodes a capsule-degrading enzyme, CapD, thought to be necessary for virulence (4,31,52) and for anchoring the capsule to the cell wall peptidoglycan (4). Poly-␥-glutamate hydrolase (PghP) is a 25-kDa enzyme encoded by the bacteriophage ⌽NIT1 that specifically cleaves D-and L-polyglutamic acid, a component of the capsule produced by several strains of B. subtilis (24).…”

Bacterial Virulence Factors: Secreted for Survival

“…On the other hand, plasmid pXO2 encodes for the proteins involved in capsule synthesis. The capsule is made up of poly-c-Dglutamic acid, that inhibits the bacterial phagocytosis during infection and is weakly immunogenic in nature [42]. Another major virulence factor is anthrolysin O, which is one of the pore forming toxins and disrupts the membrane integrity of host cells by forming homogenous pores [43].…”

Characterization of Bacillus subtilis -glutamyltransferase and its involvement in the degradation of capsule poly- -glutamate

“…However, the stereochemistry of these bacterial cPGAs depends upon the structure of the c-glutamyl linkage, and the synthesis of each cPGA is regulated differently. B. anthracis cPGA consists of D-glutamate only, and it is produced in the presence of serum or under high atmospheric CO 2 concentrations, circumstances that mimic host environments where the capsule functions as a protective barrier against phagocytosis by macrophages (Makino et al, 1988(Makino et al, , 1989(Makino et al, , 2002. On the other hand, B. subtilis produces capsule cPGA consisting of both D-and L-glutamate specifically during the early stationary phase.…”