Wed . 19 Apr 2019

Bacillus anthracis

bacillus anthracis, bacillus anthracis symptoms
Bacillus anthracis is the etiologic agent of anthrax—a common disease of livestock and, occasionally, of humans—and the only obligate pathogen within the genus Bacillus B anthracis is a Gram-positive, endospore-forming, rod-shaped bacterium, with a width of 10–12 µm and a length of 3–5 µm It can be grown in an ordinary nutrient medium under aerobic or anaerobic conditions

B anthracis belongs to the B cereus group of strains Structure of B anthracis

It is one of few bacteria known to synthesize a protein capsule poly-D-gamma-glutamic acid Like Bordetella pertussis, it forms a calmodulin-dependent adenylate cyclase exotoxin known as anthrax edema factor, along with anthrax lethal factor It bears close genotypical and phenotypical resemblance to Bacillus cereus and Bacillus thuringiensis All three species share cellular dimensions and morphology All form oval spores located centrally in an unswollen sporangium B anthracis endospores, in particular, are highly resilient, surviving extremes of temperature, low-nutrient environments, and harsh chemical treatment over decades or centuries

The endospore is a dehydrated cell with thick walls and additional layers that form inside the cell membrane It can remain inactive for many years, but if it comes into a favorable environment, it begins to grow again It initially develops inside the rod-shaped form Features such as the location within the rod, the size and shape of the endospore, and whether or not it causes the wall of the rod to bulge out are characteristic of particular species of Bacillus Depending upon the species, the endospores are round, oval, or occasionally cylindrical They are highly refractile and contain dipicolinic acid Electron micrograph sections show they have a thin outer endospore coat, a thick spore cortex, and an inner spore membrane surrounding the endospore contents The endospores resist heat, drying, and many disinfectants including 95% ethanol Because of these attributes, B anthracis endospores are extraordinarily well-suited to use in powdered and aerosol form as biological weapons Such weaponization has been accomplished in the past by at least five state bioweapons programs—those of the United Kingdom, Japan, the United States, Russia, and Iraq—and has been attempted by several others

Contents

  • 1 Historical background
  • 2 Genome structure
    • 21 pXO1 plasmid
    • 22 pXO2 plasmid
  • 3 Strains
  • 4 Evolution
    • 41 Nearest neighbors
    • 42 Pseudogene
  • 5 Clinical aspects
    • 51 Pathogenesis
    • 52 Manifestations in human disease
    • 53 Prevention and treatment
  • 6 Laboratory research
    • 61 Recent research
  • 7 Host interactions
  • 8 Sampling
  • 9 References
  • 10 External links

Historical background

CapD protein crystal structure of B anthracis

French physician Casimir Davaine 1812-1882 demonstrated the symptoms of anthrax were invariably accompanied by the microbe B anthracis German physician Aloys Pollender 1799–1879 is credited for discovery B anthracis was the first bacterium conclusively demonstrated to cause disease, by Robert Koch in 1876 The species name anthracis is from the Greek anthrax ἄνθραξ, meaning "coal" and referring to the most common form of the disease, cutaneous anthrax, in which large, black skin lesions are formed Throughout the 19th century, Anthrax was an infection that involved several very important medical developments The first vaccine containing live organisms was Louis Pasteur's veterinary anthrax vaccine

Genome structure

B anthracis has a single chromosome which is a circular, 5,227,293-bp DNA molecule It also has two circular, extrachromosomal, double-stranded DNA plasmids, pXO1 and pXO2 Both the pXO1 and pXO2 plasmids are required for full virulence and represent two distinct plasmid families

Feature Chromosome pXO1 pXO2
Size bp 5,227,293 181,677 94,829
Number of genes 5,508 217 113
Replicon coding % 843 771 762
Average gene length nt 800 645 639
G+C content % 354 325 330
rRNA operons 11 0 0
tRNAs 95 0 0
sRNAs 3 2 0
Phage genes 62 0 0
Transposon genes 18 15 6
Disrupted reading frame 37 5 7
Genes with assigned function 2,762 65 38
Conserved hypothetical genes 1,212 22 19
Genes of unknown function 657 8 5
Hypothetical genes 877 122 51

pXO1 plasmid

The pXO1 plasmid 182 kb contains the genes that encode for the anthrax toxin components: pag protective antigen, PA, lef lethal factor, LF, and cya edema factor, EF These factors are contained within a 448-kb pathogenicity island PAI The lethal toxin is a combination of PA with LF and the edema toxin is a combination of PA with EF The PAI also contains genes which encode a transcriptional activator AtxA and the repressor PagR, both of which regulate the expression of the anthrax toxin genes

pXO2 plasmid

pXO2 encodes a five-gene operon capBCADE which synthesizes a poly-γ-D-glutamic acid polyglutamate capsule This capsule allows B anthracis to evade the host immune system by protecting itself from phagocytosis Expression of the capsule operon is activated by the transcriptional regulators AcpA and AcpB, located in the pXO2 pathogenicity island 35 kb Interestingly, AcpA and AcpB expression are under the control of AtxA from pXO1

Strains

The 89 known strains of B anthracis include:

  • Sterne strain 34F2; aka the "Weybridge strain", used by Max Sterne in his 1930s vaccines
  • Vollum strain, formerly weaponized by the US, UK, and Iraq; isolated from a cow in Oxfordshire, UK, in 1935
    • Vollum M-36, virulent British research strain; passed through macaques 36 times
    • Vollum 1B, weaponized by the US and UK in the 1940s-60s
    • Vollum-14578, used in UK bio-weapons trials which severely contaminated Gruinard Island in 1942
    • V770-NP1-R, the avirulent, nonencapsulated strain used in the BioThrax vaccine
  • Anthrax 836, highly virulent strain weaponized by the USSR; discovered in Kirov in 1953
  • Ames strain, isolated from a cow in Texas in 1981; famously used in AMERITHRAX letter attacks 2001
    • Ames Ancestor
    • Ames Florida
  • H9401, isolated from human patient in Korea; used in investigational anthrax vaccines

Evolution

Whole genome sequencing has made reconstruction of the B anthracis phylogeny extremely accurate A contributing factor to the reconstruction is B anthracis being monomorphic, meaning it has low genetic diversity, including the absence of any measurable lateral DNA transfer since its derivation as a species The lack of diversity is due to a short evolutionary history that has precluded mutational saturation in single nucleotide polymorphisms

A short evolutionary time does not necessarily mean a short chronological time When DNA is replicated, mistakes occur which become genetic mutations The buildup of these mutations over time leads to the evolution of a species During the B anthracis lifecycle, it spends a significant amount of time in the soil spore reservoir stage, in which DNA replication does not occur These prolonged periods of dormancy have greatly reduced the evolutionary rate of the organism

Nearest neighbors

B anthracis belongs to the B cereus group consisting of the strains: B cereus, B anthracis, B thuringiensis, B weihenstephanensis, B mycoides, and B pseudomycoides The first three strains are pathogenic or opportunistic to insects or mammals, while the last three are not considered pathogenic The strains of this group are genetically and phenotypically heterogeneous overall, but some of the strains are more closely related and phylogenetically intermixed at the chromosome level The B cereus group generally exhibits complex genomes and most carry varying numbers of plasmids

B cereus is a soil-dwelling bacterium which can colonize the gut of invertebrates as a symbiont and is a frequent cause of food poisoning It produces an emetic toxin, enterotoxins, and other virulence factors The enterotoxins and virulence factors are encoded on the chromosome, while the emetic toxin is encoded on a 270-kb plasmid, pCER270

B thuringiensis is an insect pathogen and is characterized by production of parasporal crystals of insecticidal toxins Cry and Cyt The genes encoding these proteins are commonly located on plasmids which can be lost from the organism, making it indistinguishable from B cereus

Pseudogene

PlcR is a global transcriptional regulator which controls most of the secreted virulence factors in B cereus and B thuringiensis It is chromosomally encoded and is ubiquitous throughout the cell In B anthracis, however, the plcR gene contains a single base change at position 640, a nonsense mutation, which creates a dysfunctional protein While 1% of the B cereus group carries an inactivated plcR gene, none of them carries the specific mutation found only in B anthracis

The plcR gene is part of a two-gene operon with papR The papR gene encodes a small protein which is secreted from the cell and the reimported as a processed heptapeptide forming a quorum-sensing system The lack of PlcR in B anthracis is a principle characteristic differentiating it from other members of the B cereus group While B cereus and B thuringiensis depend on the plcR gene for expression of their virulence factors, B anthracis relies on the pXO1 and pXO2 plasmids for its virulence

Clinical aspects

Main article: Anthrax

Pathogenesis

B anthracis possesses an antiphagocytic capsule essential for full virulence The organism also produces three plasmid-coded exotoxins: edema factor, a calmodulin-dependent adenylate cyclase, causes elevation of intracellular cAMP, and is responsible for the severe edema usually seen in B anthracis infections; lethal toxin is responsible for tissue necrosis; protective antigen so named because of its use in producing protective anthrax vaccines mediates cell entry of edema factor and lethal toxin

Manifestations in human disease

The symptoms in anthrax depend on the type of infection and can take anywhere from 1 day to more than 2 months to appear All types of anthrax have the potential, if untreated, to spread throughout the body and cause severe illness and even death

Four forms of human anthrax disease are recognized based on their portal of entry

  • Cutaneous, the most common form 95%, causes a localized, inflammatory, black, necrotic lesion eschar
  • Inhalation, a rare but highly fatal form, is characterized by flu like symptoms, chest discomfort, diaphoresis, and body aches
  • Gastrointestinal, a rare but also fatal causes death to 25% type, results from ingestion of spores Symptoms include: fever and chills, swelling of neck, painful swallowing, hoarseness, nausea and vomiting especially bloody vomiting, diarrhea, flushing and red eyes, and swelling of abdomen
  • Injection, symptoms are similar to those of cutaneous anthrax, but injection anthrax can spread throughout the body faster and can be harder to recognize and treat compared to cutaneous anthrax

Prevention and treatment

A number of anthrax vaccines have been developed for preventive use in livestock and humans Anthrax vaccine adsorbed AVA may protect against cutaneous and inhalation anthrax However, this vaccine is only used for at-risk adults before exposure to anthrax and has not been approved for use after exposure Infections with B anthracis can be treated with β-lactam antibiotics such as penicillin, and others which are active against Gram-positive bacteria Penicillin-resistant B anthracis can be treated with fluoroquinolones such as ciprofloxacin or tetracycline antibiotics such as doxycycline

Laboratory research

Components of tea, such as polyphenols, have the ability to inhibit the activity both of B anthracis and its toxin considerably; spores, however, are not affected The addition of milk to the tea completely inhibits its antibacterial activity against anthrax Activity against the B athracis in the laboratory does not prove that drinking tea affects the course of an infection, since it is unknown how these polyphenols are absorbed and distributed within the body

Recent research

Advances in genotyping methods have led to improved genetic analysis for variation and relatedness These methods include multiple-locus variable-number tandem repeat analysis MLVA and typing systems using canonical single-nucleotide polymorphisms The Ames ancestor chromosome was sequenced in 2003 and contributes to the identification of genes involved in the virulence of B anthracis Recently, B anthracis isolate H9401 was isolated from a Korean patient suffering from gastrointestinal anthrax The goal of the Republic of Korea is to use this strain as a challenge strain to develop a recombinant vaccine against anthrax

The H9401 strain isolated in the Republic of Korea was sequenced using 454 GS-FLX technology and analyzed using several bioinformatics tools to align, annotate, and compare H9401 to other B anthracis strains The sequencing coverage level suggests a molecular ratio of pXO1:pXO2:chromosome as 3:2:1 which is identical to the Ames Florida and Ames Ancestor strains H9401 has 99679% sequence homology with Ames Ancestor with an amino acid sequence homology of 99870% H9401 has a circular chromosome 5,218,947 bp with 5,480 predicted ORFs, the pXO1 plasmid 181,700 bp with 202 predicted ORFs, and the pXO2 plasmid 94,824 bp with 110 predicted ORFs As compared to the Ames Ancestor chromosome above, the H9401 chromosome is about 85 kb smaller Due to the high pathogenecity and sequence similarity to the Ames Ancestor, H9401 will be used as a reference for testing the efficacy of candidate anthrax vaccines by the Republic of Korea

Since the genome of B anthracis was sequenced, alternative ways to battle this disease are being endeavored Bacteria have developed several strategies to evade recognition by the immune system The predominant mechanism for avoiding detection, employed by all bacteria is molecular camouflage Slight modifications in the outer layer that render the bacteria practically invisible to lysozymes Three of these modifications have been identified and characterized These include 1 N-glycosylation of N-acetyl-muramic acid, 2 O-acetylation of N-acetylmuramic acid and 3 N-deacetylation of N-acetyl-glucosamine Research during the last few years has focused on inhibiting such modifications As a result the enzymatic mechanism of polysaccharide de-acetylases is being investigated, that catalyze the removal of an acetyl group from N-acetyl-glucosamine and N-acetyl-muramic acid, components of the peptidoglycan layer

Host interactions

As with most other pathogenic bacteria, B anthracis must acquire iron to grow and proliferate in its host environment The most readily available iron sources for pathogenic bacteria are the heme groups used by the host in the transport of oxygen To scavenge heme from host hemoglobin and myoglobin, B anthracis uses two secretory siderophore proteins, IsdX1 and IsdX2 These proteins can separate heme from hemoglobin, allowing surface proteins of B anthracis to transport it into the cell

Sampling

The presence of B anthracis can be determined through samples taken on non-porous surfaces

References

  1. ^ a b Spencer, RC March 2003 "Bacillus anthracis" Journal of clinical pathology 56 3: 182–7 doi:101136/jcp563182 PMC 1769905  PMID 12610093 
  2. ^ Holt, J G, N R Krieg, P H A Sneath, J T Staley, and S T Williams 1994 Group 17: gram-positive cocci, p 527–558 In W R Hensyl ed, Bergey's manual of determinative bacteriology, 9th ed Williams and Wilkins, Baltimore, Md
  3. ^ Bergey's Manual of Systematic Bacteriology, vol 2, p 1105, 1986, Sneath, PHA; Mair, NS; Sharpe, ME; Holt, JG eds; Williams & Wilkins, Baltimore, Maryland, USA
  4. ^ Zilinskas, Raymond A 1999, "Iraq's Biological Warfare Program: The Past as Future", Chapter 8 in: Lederberg, Joshua editor, Biological Weapons: Limiting the Threat 1999, The MIT Press, pp 137-158
  5. ^ Théodoridès, J April 1966 "Casimir Davaine 1812-1882: a precursor of Pasteur" Medical History 10 2: 155–65 doi:101017/S0025727300010942 PMC 1033586  PMID 5325873 
  6. ^ Koch, R 1876 "Untersuchungen über Bakterien: V Die Ätiologie der Milzbrand-Krankheit, begründet auf die Entwicklungsgeschichte des Bacillus anthracis" Investigations into bacteria: V The etiology of anthrax, based on the ontogenesis of Bacillus anthracis, Cohns Beitrage zur Biologie der Pflanzen, vol 2, no 2, pages 277–310
  7. ^ Sternbach G "The History of Anthrax" Ncbi 2003: n pag Web Oct 2016
  8. ^ a b Read, TD; Peterson, SN; Tourasse, N; Baillie, LW; Paulsen, IT; Nelson, KE; Tettelin, H; Fouts, DE; Eisen, JA; Gill, SR; Holtzapple, EK; Okstad, OA; Helgason, E; Rilstone, J; Wu, M; Kolonay, JF; Beanan, MJ; Dodson, RJ; Brinkac, LM; Gwinn, M; DeBoy, RT; Madpu, R; Daugherty, SC; Durkin, AS; Haft, DH; Nelson, WC; Peterson, JD; Pop, M; Khouri, HM; Radune, D; Benton, JL; Mahamoud, Y; Jiang, L; Hance, IR; Weidman, JF; Berry, KJ; Plaut, RD; Wolf, AM; Watkins, KL; Nierman, WC; Hazen, A; Cline, R; Redmond, C; Thwaite, JE; White, O; Salzberg, SL; Thomason, B; Friedlander, AM; Koehler, TM; Hanna, PC; Kolstø, AB; Fraser, CM May 1, 2003 "The genome sequence of Bacillus anthracis Ames and comparison to closely related bacteria" Nature 423 6935: 81–6 doi:101038/nature01586 PMID 12721629 
  9. ^ a b c d e f g Kolstø, Anne-Brit; Tourasse, Nicolas J; Økstad, Ole Andreas 1 October 2009 "What Sets Apart from Other Species" Annual Review of Microbiology 63 1: 451–476 doi:101146/annurevmicro091208073255 
  10. ^ a b c d Chun, J-H; Hong, K-J; Cha, S H; Cho, M-H; Lee, K J; Jeong, D H; Yoo, C-K; Rhie, G-e 18 July 2012 "Complete Genome Sequence of Bacillus anthracis H9401, an Isolate from a Korean Patient with Anthrax" Journal of Bacteriology 194 15: 4116–4117 doi:101128/JB00159-12 PMC 3416559  PMID 22815438 
  11. ^ a b Keim, Paul; Gruendike, Jeffrey M; Klevytska, Alexandra M; Schupp, James M; Challacombe, Jean; Okinaka, Richard 1 December 2009 "The genome and variation of Bacillus anthracis" Molecular Aspects of Medicine 30 6: 397–405 doi:101016/jmam200908005 PMC 3034159  PMID 19729033 
  12. ^ Jensen, G B; Hansen, B M; Eilenberg, J; Mahillon, J 18 July 2003 "The hidden lifestyles of Bacillus cereus and relatives" Environmental Microbiology 5 8: 631–640 doi:101046/j1462-2920200300461x PMID 12871230 
  13. ^ Drobniewski, FA October 1993 "Bacillus cereus and related species" Clinical Microbiology Reviews 6 4: 324–38 PMC 358292  PMID 8269390 
  14. ^ Stenfors Arnesen, Lotte P; Fagerlund, Annette; Granum, Per Einar 1 July 2008 "From soil to gut: and its food poisoning toxins" FEMS Microbiology Reviews 32 4: 579–606 doi:101111/j1574-6976200800112x PMID 18422617 
  15. ^ Schnepf, E; Crickmore, N; Van Rie, J; Lereclus, D; Baum, J; Feitelson, J; Zeigler, DR; Dean, DH September 1998 "Bacillus thuringiensis and its pesticidal crystal proteins" Microbiology and molecular biology reviews : MMBR 62 3: 775–806 PMC 98934  PMID 9729609 
  16. ^ Agaisse, H; Gominet, M; Okstad, OA; Kolstø, AB; Lereclus, D June 1999 "PlcR is a pleiotropic regulator of extracellular virulence factor gene expression in Bacillus thuringiensis" Molecular Microbiology 32 5: 1043–53 doi:101046/j1365-2958199901419x PMID 10361306 
  17. ^ Slamti, L; Perchat, S; Gominet, M; Vilas-Bôas, G; Fouet, A; Mock, M; Sanchis, V; Chaufaux, J; Gohar, M; Lereclus, D June 2004 "Distinct mutations in PlcR explain why some strains of the Bacillus cereus group are nonhemolytic" Journal of Bacteriology 186 11: 3531–8 doi:101128/JB186113531-35382004 PMC 415780  PMID 15150241 
  18. ^ Okstad, OA; Gominet, M; Purnelle, B; Rose, M; Lereclus, D; Kolstø, AB November 1999 "Sequence analysis of three Bacillus cereus loci carrying PIcR-regulated genes encoding degradative enzymes and enterotoxin" Microbiology 145 11: 3129–38 doi:101099/00221287-145-11-3129 PMID 10589720 
  19. ^ a b Slamti, L; Lereclus, D Sep 2, 2002 "A cell-cell signaling peptide activates the PlcR virulence regulon in bacteria of the Bacillus cereus group" The EMBO Journal 21 17: 4550–9 doi:101093/emboj/cdf450 PMC 126190  PMID 12198157 
  20. ^ Bouillaut, L; Perchat, S; Arold, S; Zorrilla, S; Slamti, L; Henry, C; Gohar, M; Declerck, N; Lereclus, D June 2008 "Molecular basis for group-specific activation of the virulence regulator PlcR by PapR heptapeptides" Nucleic Acids Research 36 11: 3791–801 doi:101093/nar/gkn149 PMC 2441798  PMID 18492723 
  21. ^ a b c d "Symptoms" Centers for Disease Control and Prevention Retrieved 16 November 2015 
  22. ^ https://wwwcdcgov/anthrax/medicalcare/prevention/antibioticshtml
  23. ^ Barnes JM 1947 "Penicillin and B anthracis" J Path Bacteriol 194: 113–125 doi:101002/path1700590113 
  24. ^ "Anthrax and tea" Society for Applied Microbiology 2011-12-21 Archived from the original on February 13, 2009 Retrieved 2011-12-21 
  25. ^ Callewaert L, Michiels CW Lysozymes in the animal kingdom J Biosci 351: 2010; 127-60
  26. ^ Balomenou, Stavroula, Sofia Arnaouteli, Dimitris Koutsioulis, Vassiliki E Fadouloglou, and Vassilis Bouriotis "Polysaccharide Deacetylases: New Antibacterial Drug Targets"Frontiers in Anti-Infective Drug Discovery 4 2015: 68-130
  27. ^ Maresso AW, Garufi G, Schneewind O 2008 "Bacillus anthracis Secretes Proteins That Mediate Heme Acquisition from Hemoglobin" PLOS Pathogens 4 8: e1000132 doi:101371/journalppat1000132 

External links

  • Bacillus anthracis genomes and related information at PATRIC, a Bioinformatics Resource Center funded by NIAID
  • Hazards in Animal Research Database - Bacillus anthracis
  • Pathema-Bacillus Resource

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