Which structural feature is associated with Bacillus anthracis?

Bacillus anthracis, the causative agent of anthrax, is particularly known for its distinctive colony morphology when cultured on certain media, such as blood agar. The "medusa head" appearance refers to the irregular edges and the frilled or undulating surface of the colonies, resembling the legendary Medusa from Greek mythology. This unique morphological characteristic aids microbiologists in identifying Bacillus anthracis in laboratory settings.

The other options do not accurately describe Bacillus anthracis. While Bacillus anthracis is a Gram-positive rod, it is not Gram-negative nor does it form long spore chains. Instead, it typically produces spores individually or in short chains. Additionally, Bacillus anthracis is aerobic or facultatively anaerobic, meaning it can grow in both the presence and absence of oxygen, which contrasts with the assertion that it is strictly anaerobic. Understanding these features is crucial for the proper identification and handling of this pathogen in clinical microbiology.