bacillus circulans bacillus circulans bacillus circulans is a soil-dwelling human pathogen which has been associated with "septicemia, mixed abscess infections, and wound infections", as well as with meningitis. bacillus circulans scientific classification domain: bacteria phylum: bacillota class: bacilli order: bacillales family: bacillaceae genus: bacillus species: b. circulans binomial name bacillus circulansjordan, 1890 this species has been recently transferred into the genus niallia. the correct nomenclature is niallia circulans. morphology staining gram-positive, gram-variable or gram-negative. positive spore stain result. vegetative cell straight, occasionally curved rods, 2.0-4.2 x 0.5-0.8 μm, motile by peritrichous flagella. spores has ellipsoidal spores which are subterminal or terminal; swelling the sporangia. these are "centrally located" and either cylindrical or "kidney-shaped".