Which Bacillus species is nonmotile?

Which Bacillus species is nonmotile?

• A. Bacillus cereus
• B. Bacillus subtilis
• C. Bacillus anthracis
• D. Bacillus thuringiensis

Answer: (C)

Motility differences among Bacillus species are a classic way to differentiate them in the lab. Most Bacillus rods are motile because they have flagella, so they can move in semi-solid media or on slides. Bacillus anthracis is an exception: it lacks flagella, so it does not move in motility tests and is considered nonmotile. This nonmotility helps distinguish it from other Bacillus species such as Bacillus cereus, Bacillus subtilis, and Bacillus thuringiensis, which are typically motile. In practice, noting nonmotility alongside its capsule and virulence factors further supports its identification as the species associated with anthrax.

Motility differences among Bacillus species are a classic way to differentiate them in the lab. Most Bacillus rods are motile because they have flagella, so they can move in semi-solid media or on slides. Bacillus anthracis is an exception: it lacks flagella, so it does not move in motility tests and is considered nonmotile. This nonmotility helps distinguish it from other Bacillus species such as Bacillus cereus, Bacillus subtilis, and Bacillus thuringiensis, which are typically motile. In practice, noting nonmotility alongside its capsule and virulence factors further supports its identification as the species associated with anthrax.