|Bacillus anthracis - solid & liquid media
Phylum Firmicutes, Class Bacilli, Order Bacillales, Family Bacillaceae, Genus Bacillus, Bacillus anthracis Cohn 1872
Old synonym: B. cereus var. anthracis Smith, Gordon and Clark,1946; Bacteridium anthracis (Cohn) Hauduroy et al. 1953.
Closely related to Bacillus cereus.
Can be distinguished from other members of the B. cereus group by AFLP (amplified
fragment length polymorphism) analysis; Ba813 DNA sequence (277 bp) is specific
chromosomal marker for B. anthracis and in combination with sequencing of parts of
lef and cap genes its sequence allows the identification of virulent strains.
Gram-positive, straight, large, 3-6 / 1-1.25 μm, noncilliated bacilli, forming chains or
filaments. Ellipsoidal, non-deforming spore located central or para-central .
Nonmotile. Capsulate. Capsule is produced ‘in vivo’ or in blood containing medium
(or medium with ascitic liquid). the capsule can be visualized by staining smears with
M’Fadyean’s polychrome methylene blue or India ink.
Aerobic, facultative anaerobic. Grow easily on simple media. Growth temperature
min. 15ºC - max. 40 ºC. NaCl not required for growth.
In liquid medium produce low turbidity , cotton-like agglutination.
Colonies on agar are large, 6-7 mm diameter, opaque, non-pigmented; R-type
Nonhemolytic; colonies of the capsulate strains appear mucoid.
Soil inhabitant in sporulated form. Isolated from blood of animals and humans with
anthrax, animal carcasses and products and soil contamined with spores .
Usually susceptible to penicillin. Susceptible to gamma phage.
Grow with lysozyme present
Pathogenicity factors: capsule, enzymes (lecithinase, proteases, colagenase), toxin.
Virulence genes are carried by plasmids pX01 (toxins) and pX02 (capsule); these
plasmids may be transmissible to other members of the B. cereus group.
Causes anthrax (septicaemia) to all mammalians, rarely to birds. In humans,
pathogenic strains can produce skin infection ( black – anthrakitis gr.) or intestinal,
pulmonary, meningeal infections. Non-virulent strains can produce bacteremia.
Experimental infection on mice, rats, rabbits, hamsters, chimps.
- Bîlbîie V., Pozsgi N., 1985, Bacteriologie Medicală, vol.ll, Ed. Medicală, Bucureşti.
- Gordon R.E., Haynes W.C., Pang C.H. (1973) – The genus Bacillus . Agriculture Handbook No. 427, U.S.D.A., Washington D.C.
- Buchanan R.E., Gibbons N.E., Cowan S.T., Holt J.G., Liston J., Murray R.G.E., Niven C.F., Ravin A.W., Stanier R.W. (1974) - Bergey’s
Manual of Determinative Bacteriology, Eight Edition, The Williams & Wilkins Company, Baltimore.
- Buiuc D., Negut M. , 2009. Tratat de Microbiologie Clinica, editia a III-a, Editura Medicala, Bucuresti.
- N.A. Logan and P. De Vos, 2009. Genus I. Bacillus Cohn 1872. In: (Eds.) P.D. Vos, G. Garrity, D. Jones, N.R. Krieg, W. Ludwig, F.A.
Rainey, K.-H. Schleifer, W.B. Whitman. Bergey’s Manual of Systematic Bacteriology, Volume 3: The Firmicutes, Springer, 21-127.
Positive results for nitrate reduction, Voges-Proskauer reaction, decomposition of
gelatin, casein hydrolysis, starch hydrolysis, catalase, egg-yolk reaction, acid
production from glucose & glycogen.
Negative results for indole production, degradation of tyrosine, urease, acid production
from: arabinose, mannitol, xylose, D-mannose, methyl β-xyloside, glycerol & salicin.
(c) Costin Stoica
|Malachite-green-stained, central, non-deforming
spores (Bacillus anthracis)