Bacillus anthracis

About: Bacillus anthracis is a research topic. Over the lifetime, 3994 publications have been published within this topic receiving 128122 citations.

The bifunctional cell wall hydrolase CwlT is needed for conjugation of the integrative and conjugative element ICEBs1 in Bacillus subtilis and B. anthracis

Abstract: The mobile genetic element ICEBs1 is an integrative and conjugative element (ICE) found in Bacillus subtilis. One of the ICEBs1 genes, cwlT, encodes a cell wall hydrolase with two catalytic domains, a muramidase and a peptidase. We found that cwlT is required for ICEBs1 conjugation. We examined the role of each of the two catalytic domains and found that the muramidase is essential, whereas the peptidase is partially dispensable for transfer of ICEBs1. We also found that the putative signal peptide in CwlT is required for CwlT to function in conjugation, consistent with the notion that CwlT is normally secreted from the cytoplasm. We found that alteration of the putative lipid attachment site on CwlT had no effect on its role in conjugation, indicating that if CwlT is a lipoprotein, the lipid attachment is not required for conjugation. Finally, we found conditions supporting efficient transfer of ICEBs1 into and out of Bacillus anthracis and that cwlT was needed for ICEBs1 to function in B. anthracis. The mature cell wall of B. anthracis is resistant to digestion by CwlT, indicating that CwlT might act during cell wall synthesis, before modifications of the peptidoglycan are complete.

Imaging and analysis of Bacillus anthracis spore germination

Abstract: External and internal changes occurring during the process of germination of Bacillus anthracis spores were observed through atomic force microscopy (AFM) and transmission electron microscopy (TEM), respectively. AFM studies showed that in response to L-alanine (4 mM), as a germinant, the spore germinates into a vegetative cell in 3 hours. The temporal size changes occurring during the germination were gradual but the major change in size was observed between the second and third hour. TEM of spores showed the presence of varied layers, which is in accordance with previous studies. However, the integrity of these layers was lost gradually during the process of germination. The inner spore membrane remains intact even until late stages of germination, whereas the coat, outer spore membrane, and the cortical layers are discarded at the second-hour stage. The results indicate that sequential changes during the germination of a B. anthracis spore are similar to other species of the Bacillus group.

Killed but Metabolically Active Bacillus anthracis Vaccines Induce Broad and Protective Immunity against Anthrax

Abstract: Bacillus anthracis is the causative agent of anthrax. We have developed a novel whole-bacterial-cell anthrax vaccine utilizing B. anthracis that is killed but metabolically active (KBMA). Vaccine strains that are asporogenic and nucleotide excision repair deficient were engineered by deleting the spoIIE and uvrAB genes, rendering B. anthracis extremely sensitive to photochemical inactivation with S-59 psoralen and UV light. We also introduced point mutations into the lef and cya genes, which allowed inactive but immunogenic toxins to be produced. Photochemically inactivated vaccine strains maintained a high degree of metabolic activity and secreted protective antigen (PA), lethal factor, and edema factor. KBMA B. anthracis vaccines were avirulent in mice and induced less injection site inflammation than recombinant PA adsorbed to aluminum hydroxide gel. KBMA B. anthracis-vaccinated animals produced antibodies against numerous anthrax antigens, including high levels of anti-PA and toxin-neutralizing antibodies. Vaccination with KBMA B. anthracis fully protected mice against challenge with lethal doses of toxinogenic unencapsulated Sterne 7702 spores and rabbits against challenge with lethal pneumonic doses of fully virulent Ames strain spores. Guinea pigs vaccinated with KBMA B. anthracis were partially protected against lethal Ames spore challenge, which was comparable to vaccination with the licensed vaccine anthrax vaccine adsorbed. These data demonstrate that KBMA anthrax vaccines are well tolerated and elicit potent protective immune responses. The use of KBMA vaccines may be broadly applicable to bacterial pathogens, especially those for which the correlates of protective immunity are unknown.

Recombinant Anthrax Toxin Receptor-Fc Fusion Proteins Produced in Plants Protect Rabbits against Inhalational Anthrax

Abstract: Inhalational anthrax, a zoonotic disease caused by the inhalation of Bacillus anthracis spores, has a ∼50% fatality rate even when treated with antibiotics. Pathogenesis is dependent on the activity of two toxic noncovalent complexes: edema toxin (EdTx) and lethal toxin (LeTx). Protective antigen (PA), an essential component of both complexes, binds with high affinity to the major receptor mediating the lethality of anthrax toxin in vivo, capillary morphogenesis protein 2 (CMG2). Certain antibodies against PA have been shown to protect against anthrax in vivo. As an alternative to anti-PA antibodies, we produced a fusion of the extracellular domain of human CMG2 and human IgG Fc, using both transient and stable tobacco plant expression systems. Optimized expression led to the CMG2-Fc fusion protein being produced at high levels: 730 mg/kg fresh leaf weight in Nicotiana benthamiana and 65 mg/kg in N. tabacum. CMG2-Fc, purified from tobacco plants, fully protected rabbits against a lethal challenge with B. anthracis spores at a dose of 2 mg/kg body weight administered at the time of challenge. Treatment with CMG2-Fc did not interfere with the development of the animals' own immunity to anthrax, as treated animals that survived an initial challenge also survived a rechallenge 30 days later. The glycosylation of the Fc (or lack thereof) had no significant effect on the protective potency of CMG2-Fc in rabbits or on its serum half-life, which was about 5 days. Significantly, CMG2-Fc effectively neutralized, in vitro, LeTx-containing mutant forms of PA that were not neutralized by anti-PA monoclonal antibodies.