Bacillus Anthracis infection
Species of the genus Bacillus bacteria are straight (or nearly straight), with square or rounded ends, varying in size (0.5 x 1.2 m x 2.5 m to 10 m m), sporulated at Gram positive or Gram-variable (frequently Gram stain is positive in young cultures), generally with a mobile ciliature peritrichous ( ¤ Bacillus anthracis and Bacillus mycoides are immobile and mobile species, mobility is variable depending on the strain), sometimes encapsulated ( ¤ Bacillus anthracis, Bacillus licheniformis, Bacillus megaterium and Bacillus subtilis can develop a capsule formed of a polymer of glutamic acid), aerobic or anaerobic-aero, mostly catalase positive, giving a variable response to the oxidase test.
The culture of these germs can be difficult because some species require many growth factors. The appearance of colonies obtained on agar medium is highly variable and the phenomena of dissociation are common.
Bacillus anthracis, Bacillus cereus, Bacillus thuringiensis and Bacillus weihenstephanensis give large colonies (2-7 mm), matt or granular form which is variable (circular or not, or jagged edges or regular filamentous).
Bacillus mycoides and Bacillus pseudomycoides give rhizoid adherent colonies which spread over the entire agar and cover the entire surface of the medium in 48 hours.
The colonies of Bacillus licheniformis have an aspect of lichen, they are dry and adherent to the agar
Bacillus subtilis produces colonies of irregular shapes (contours that may be wavy or filaments), creamy and with a diameter between 2 and 4 mm. In older cultures, the colonies take on a dry, rough and they become embedded in the agar
Bacillus circulans gave colonies that invade agar (swarming).
The colonies of other species isolated in medical bacteriology (Bacillus coagulans, Bacillus megaterium, Bacillus pumilus) have no special characteristics.
Certain species or strains produce pigments when grown in specific environments (red pigment Bacillus cereus, Bacillus fastidiosus pigment yellow, pigment yellow, orange, brown or pink for Bacillus subtilis)
When conditions become unfavorable, Bacillus sporulate and produce spores (one spore per vegetative cell) are often very resistant in the environment. The phenomenon of sporulation, in contrast to what happens to species of the genus Clostridium, is not inhibited by oxygen. Sporulation depends on the culture conditions and, in vitro, some species sporulate in special media.
Traditionally, the genus Bacillus are divided into 3 groups according to the morphology of the spore and sporangium:
Group I consists of Gram positive, spore with a central or terminal, spherical or ovoid, does not deform the cell. This group is divided into two subgroups: group IA consists of bacilli with a diameter greater than 1 m m and containing inclusions of poly-beta-hydroxybutyrate ( Bacillus anthracis, ¤ Bacillus cereus, Bacillus megaterium, Bacillus mycoides, pseudomycoides Bacillus, Bacillus thuringiensis, ¤ Bacillus weihenstephanensis) and group IB collecting bacilli with a diameter less than 1 m m and without inclusions of poly-beta-hydroxybutyrate (Bacillus coagulans, Bacillus firmus, Bacillus licheniformis, Bacillus subtilis , Bacillus pumilus)
Group II consists of gram-variable species, with an ovoid spore, central or terminal deformans (Bacillus circulans, Bacillus stearothermophilus)
Group III is characterized by Gram variable with a spore spherical, deforming, terminal or sub-terminal (Bacillus globisporus, Bacillus insolitus)
Some species, including Bacillus thuringiensis, are capable of synthesizing a crystal or parasporal body containing toxins lethal to insects. The development of a parasporal body is not unique as the only genus Bacillus fusiformis Lysinibacillus, Lysinibacillus sphaericus, Paenibacillus popilliae, Brevibacillus laterosporus and some strains of Paenibacillus lentimorbus are capable of forming such crystals.