On Gram stain, Bacillus anthracis appears as a large, spore-forming gram-positive bacillus that characteristically grows in which arrangement?

On Gram stain, Bacillus anthracis appears as a large, spore-forming gram-positive bacillus that characteristically grows in which arrangement?

• A. Cocci in clusters
• B. Pears
• C. Long chains
• D. Random short chains

Answer: (C)

Arrangement on Gram stain reflects how Bacillus species divide and stay attached after division. Bacillus anthracis is a large gram-positive rod that forms spores, and it typically appears in long, continuous chains because the daughter cells remain attached as they separate. This chaining is a characteristic clue for this organism in stained preparations. Other patterns—cocci in clusters would suggest Staphylococcus species; a pear-shaped or randomly short chain appearance does not fit this organism—emphasizing that the hallmark is the long chain of bacilli.

Arrangement on Gram stain reflects how Bacillus species divide and stay attached after division. Bacillus anthracis is a large gram-positive rod that forms spores, and it typically appears in long, continuous chains because the daughter cells remain attached as they separate. This chaining is a characteristic clue for this organism in stained preparations. Other patterns—cocci in clusters would suggest Staphylococcus species; a pear-shaped or randomly short chain appearance does not fit this organism—emphasizing that the hallmark is the long chain of bacilli.