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Microbiology Spectrum Oct 2015In some Bacillus species, including Bacillus subtilis, the coat is the outermost layer of the spore. In others, such as the Bacillus cereus family, there is an... (Review)
Review
In some Bacillus species, including Bacillus subtilis, the coat is the outermost layer of the spore. In others, such as the Bacillus cereus family, there is an additional layer that envelops the coat, called the exosporium. In the case of Bacillus anthracis, a series of fine hair-like projections, also referred to as a "hairy" nap, extends from the exosporium basal layer. The exact role of the exosporium in B. anthracis, or for any of the Bacillus species possessing this structure, remains unclear. However, it has been assumed that the exosporium would play some role in infection for B. anthracis, because it is the outermost structure of the spore and would make initial contact with host and immune cells during infection. Therefore, the exosporium has been a topic of great interest, and over the past decade much progress has been made to understand its composition, biosynthesis, and potential roles. Several key aspects of this spore structure, however, are still debated and remain undetermined. Although insights have been gained on the interaction of exosporium with the host during infection, the exact role and significance of this complex structure remain to be determined. Furthermore, because the exosporium is a highly antigenic structure, future strategies for the next-generation anthrax vaccine should pursue its inclusion as a component to provide protection against the spore itself during the initial stages of anthrax.
Topics: Bacillus anthracis; Bacterial Proteins; Host-Pathogen Interactions; Microscopy, Electron, Transmission; Spores, Bacterial
PubMed: 26542035
DOI: 10.1128/microbiolspec.TBS-0021-2015 -
Molecular Aspects of Medicine Dec 2009Bacillus anthracis is a member of the Bacillus cereus group species (also known as the "group 1 bacilli"), a collection of Gram-positive spore-forming soil bacteria that... (Review)
Review
Bacillus anthracis is a member of the Bacillus cereus group species (also known as the "group 1 bacilli"), a collection of Gram-positive spore-forming soil bacteria that are non-fastidious facultative anaerobes with very similar growth characteristics and natural genetic exchange systems. Despite their close physiology and genetics, the B. cereus group species exhibit certain species-specific phenotypes, some of which are related to pathogenicity. B. anthracis is the etiologic agent of anthrax. Vegetative cells of B. anthracis produce anthrax toxin proteins and a poly-d-glutamic acid capsule during infection of mammalian hosts and when cultured in conditions considered to mimic the host environment. The genes associated with toxin and capsule synthesis are located on the B. anthracis plasmids, pXO1 and pXO2, respectively. Although plasmid content is considered a defining feature of the species, pXO1- and pXO2-like plasmids have been identified in strains that more closely resemble other members of the B. cereus group. The developmental nature of B. anthracis and its pathogenic (mammalian host) and environmental (soil) lifestyles of make it an interesting model for study of niche-specific bacterial gene expression and physiology.
Topics: Animals; Anthrax; Antigens, Bacterial; Bacillus anthracis; Bacterial Capsules; Bacterial Proteins; Bacterial Toxins; Bacteriophages; Conjugation, Genetic; Environment; Gene Expression Regulation, Bacterial; Genome, Bacterial; Phenotype; Plasmids; Soil Microbiology
PubMed: 19654018
DOI: 10.1016/j.mam.2009.07.004 -
Infection, Genetics and Evolution :... Aug 2011Bacillus anthracis, the etiological agent of anthrax, manifests a particular bimodal lifestyle. This bacterial species alternates between short replication phases of... (Review)
Review
Bacillus anthracis, the etiological agent of anthrax, manifests a particular bimodal lifestyle. This bacterial species alternates between short replication phases of 20-40 generations that strictly require infection of the host, normally causing death, interrupted by relatively long, mostly dormant phases as spores in the environment. Hence, the B. anthracis genome is highly homogeneous. This feature and the fact that strains from nearly all parts of the world have been analysed for canonical single nucleotide polymorphisms (canSNPs) and variable number tandem repeats (VNTRs) has allowed the development of molecular epidemiological and molecular clock models to estimate the age of major diversifications in the evolution of B. anthracis and to trace the global spread of this pathogen, which was mostly promoted by movement of domestic cattle with settlers and by international trade of contaminated animal products. From a taxonomic and phylogenetic point of view, B. anthracis is a member of the Bacillus cereus group. The differentiation of B. anthracis from B. cereus sensu stricto, solely based on chromosomal markers, is difficult. However, differences in pathogenicity clearly differentiate B. anthracis from B. cereus and are marked by the strict presence of virulence genes located on the two virulence plasmids pXO1 and pXO2, which both are required by the bacterium to cause anthrax. Conversely, anthrax-like symptoms can also be caused by organisms with chromosomal features that are more closely related to B. cereus, but which carry these virulence genes on two plasmids that largely resemble the B. anthracis virulence plasmids.
Topics: Animals; Bacillus anthracis; Biological Evolution; Host-Pathogen Interactions; Humans; Phylogeny; Phylogeography; Virulence
PubMed: 21640849
DOI: 10.1016/j.meegid.2011.05.013 -
Annual Review of Microbiology 2015Anthrax is caused by the spore-forming, gram-positive bacterium Bacillus anthracis. The bacterium's major virulence factors are (a) the anthrax toxins and (b) an... (Review)
Review
Anthrax is caused by the spore-forming, gram-positive bacterium Bacillus anthracis. The bacterium's major virulence factors are (a) the anthrax toxins and (b) an antiphagocytic polyglutamic capsule. These are encoded by two large plasmids, the former by pXO1 and the latter by pXO2. The expression of both is controlled by the bicarbonate-responsive transcriptional regulator, AtxA. The anthrax toxins are three polypeptides-protective antigen (PA), lethal factor (LF), and edema factor (EF)-that come together in binary combinations to form lethal toxin and edema toxin. PA binds to cellular receptors to translocate LF (a protease) and EF (an adenylate cyclase) into cells. The toxins alter cell signaling pathways in the host to interfere with innate immune responses in early stages of infection and to induce vascular collapse at late stages. This review focuses on the role of anthrax toxins in pathogenesis. Other virulence determinants, as well as vaccines and therapeutics, are briefly discussed.
Topics: Animals; Anthrax; Antigens, Bacterial; Bacillus anthracis; Bacterial Capsules; Bacterial Toxins; Humans; Spores, Bacterial
PubMed: 26195305
DOI: 10.1146/annurev-micro-091014-104523 -
Journal of Microbiological Methods Jul 2010Bacillus anthracis is a Gram-positive, spore-forming bacterium representing the etiological agent of acute infectious disease anthrax, a lethal but rare disease of... (Review)
Review
Bacillus anthracis is a Gram-positive, spore-forming bacterium representing the etiological agent of acute infectious disease anthrax, a lethal but rare disease of animals and humans in nature. With recent use of anthrax as a bioweapon, a number of techniques have been recently developed and evaluated to facilitate its rapid detection of B. anthracis in the environment as well as in point-of-care settings for humans suspected of exposure to the pathogen. Complex laboratory methods for B. anthracis identification are required since B. anthracis has similarities with other Bacillus species and its existence in both spore and vegetative forms. This review discusses current challenges and various improvements associated with anthrax agent detection.
Topics: Animals; Anthrax; Bacillus anthracis; Bacteriological Techniques; Clinical Laboratory Techniques; Humans
PubMed: 20399814
DOI: 10.1016/j.mimet.2010.04.005 -
International Journal of Medical... Jul 2008Anthrax Euronet, a Coordination Action of the EU 6th Framework Programme, was designed to strengthen networking activities between anthrax research groups in Europe and... (Review)
Review
Anthrax Euronet, a Coordination Action of the EU 6th Framework Programme, was designed to strengthen networking activities between anthrax research groups in Europe and to harmonise protocols for testing anthrax vaccines and therapeutics. Inevitably, the project also addressed aspects of the current political issues of biosecurity and dual-use research, i.e. research into agents of important diseases of man, livestock or agriculture that could be used as agents of bioterrorism. This review provides a comprehensive overview of the biology of Bacillus anthracis, of the pathogenesis, epidemiology and diagnosis of anthrax, as well as vaccine and therapeutic intervention strategies. The proposed requirement for a code of conduct for working with dual-use agents such as the anthrax bacillus is also discussed.
Topics: Animals; Anthrax; Anthrax Vaccines; Bacillus anthracis; Humans; Virulence Factors
PubMed: 18375178
DOI: 10.1016/j.ijmm.2007.09.007 -
Future Microbiology Oct 2009Bacillus anthracis is a Gram-positive, spore-forming bacterium representing the etiological cause of anthrax, a rare lethal disease of animals and humans. Development of... (Review)
Review
Bacillus anthracis is a Gram-positive, spore-forming bacterium representing the etiological cause of anthrax, a rare lethal disease of animals and humans. Development of anthrax countermeasures has gained increasing attention owing to the potential use of B. anthracis spores as a bioterror weapon. The various forms of infection by B. anthracis are characterized both by toxemia and septicemia, both of which are the result of spore entry into the host followed by their germination into rapidly multiplying, toxin-producing bacilli. Following the publication of the bacterial genome, proteomic studies were carried out to determine the protein composition of the spore and identify exposed vegetative (membrane-located or secreted) proteins. These studies included comparison of strains differing in their virulence, cultured under different conditions and, in some cases, were complemented by serological inspection, which addressed expression during infection of proteomically identified proteins and their immunogenicity. The proteomic approach emerged as a valuable strategy for the generation of a pool of potential B. anthracis protein targets for further evaluation in detection, diagnostics, therapy and prophylaxis, and contributed to the elucidation of some aspects of the pathogenesis of the disease.
Topics: Animals; Anthrax; Bacillus anthracis; Bacterial Proteins; Gene Expression Profiling; Humans; Mice; Proteome; Proteomics; Spores, Bacterial; Virulence Factors
PubMed: 19824790
DOI: 10.2217/fmb.09.73 -
Emerging Infectious Diseases Oct 2005Pyrosequencing technology is a sequencing method that screens DNA nucleotide incorporation in real time. A set of coupled enzymatic reactions, together with...
Pyrosequencing technology is a sequencing method that screens DNA nucleotide incorporation in real time. A set of coupled enzymatic reactions, together with bioluminescence, detects incorporated nucleotides in the form of light pulses, which produces a profile of characteristic peaks in a pyrogram. We used this technology to identify the warfare agent Bacillus anthracis by sequencing 4 single nucleotide polymorphisms (SNPs) in the rpoB gene as chromosomal markers for B. anthracis. In addition, 1 segment in each of the B. anthracis plasmids pXO1 and pXO2 was analyzed to determine the virulence status of the bacterial strains. Pyrosequencing technology is a powerful method to identify B. anthracis.
Topics: Animals; Bacillus; Bacillus anthracis; Bacterial Typing Techniques; DNA-Directed RNA Polymerases; Genotype; Humans; Plasmids; Polymerase Chain Reaction; Polymorphism, Single Nucleotide; Sequence Analysis, DNA; Species Specificity; Virulence
PubMed: 16318691
DOI: 10.3201/eid1110.041316 -
World Journal of Microbiology &... May 2014Characterization of candidate surrogate spores prior to experimental use is critical to confirm that the surrogate characteristics are as closely similar as possible to... (Review)
Review
Characterization of candidate surrogate spores prior to experimental use is critical to confirm that the surrogate characteristics are as closely similar as possible to those of the pathogenic agent of interest. This review compares the physical properties inherent to spores of Bacillus anthracis (Ba) and Bacillus thuringiensis (Bt) that impact their movement in air and interaction with surfaces, including size, shape, density, surface morphology, structure and hydrophobicity. Also evaluated is the impact of irradiation on the physical properties of both Bacillus species. Many physical features of Bt and Ba have been found to be similar and, while Bt is considered typically non-pathogenic, it is in the B. cereus group, as is Ba. When cultured and sporulated under similar conditions, both microorganisms share a similar cylindrical pellet shape, an aerodynamic diameter of approximately 1 μm (in the respirable size range), have an exosporium with a hairy nap, and have higher relative hydrophobicities than other Bacillus species. While spore size, morphology, and other physical properties can vary among strains of the same species, the variations can be due to growth/sporulation conditions and may, therefore, be controlled. Growth and sporulation conditions are likely among the most important factors that influence the representativeness of one species, or preparation, to another. All Bt spores may, therefore, not be representative of all Ba spores. Irradiated spores do not appear to be a good surrogate to predict the behavior of non-irradiated spores due to structural damage caused by the irradiation. While the use of Bt as a surrogate for Ba in aerosol testing appears to be well supported, this review does not attempt to narrow selection between Bt strains. Comparative studies should be performed to test the hypothesis that viable Ba and Bt spores will behave similarly when suspended in the air (as an aerosol) and to compare the known microscale characteristics versus the macroscale response.
Topics: Aerosols; Bacillus anthracis; Bacillus thuringiensis; Humans; Spores, Bacterial
PubMed: 24338558
DOI: 10.1007/s11274-013-1576-x -
Molecular Aspects of Medicine Dec 2009The global distribution of anthrax is largely determined by soils with high calcium levels and a pH above 6.1, which foster spore survival. It is speculated that the... (Review)
Review
The global distribution of anthrax is largely determined by soils with high calcium levels and a pH above 6.1, which foster spore survival. It is speculated that the spore exosporium probably plays a key part by restricting dispersal and thereby increasing the probability of a grazing animal acquiring a lethal dose. 'Anthrax Seasons' are characterized by hot-dry weather which stresses animals and reduces their innate resistance to infection allowing low doses of spores to be infective. Necrophagic flies act as case-multipliers and haemophagic flies as space-multipliers; the latter are aided by climatic factors which play a key part in whether epidemics occur. Host death is a function of species sensitivity to the toxins. The major function of scavengers is to open the carcass, spill fluids, and thereby aid bacilli dispersal and initiate sporulation. In the context of landscape ecology viable spore distribution is a function of mean annual temperature, annual precipitation, elevation, mean NDVI, annual NDVI amplitude, soil moisture content, and soil pH.
Topics: Animals; Anthrax; Bacillus anthracis; Climate; Disease Reservoirs; Ecology; Humans; Hydrogen-Ion Concentration; Seasons; Soil Microbiology; Spores, Bacterial
PubMed: 19720074
DOI: 10.1016/j.mam.2009.08.003