Medusa head appearance is a feature of
Bacillus anthracis:When grown on blood agar plates, the organisms produce nonhemolytic gray to white, tenacious colonies with a rough texture and a ground-glass appearance. Comma-shaped outgrowths (Medusa head, "curled hair") may project from the colony.Reference: Jawetz, Melnick, & Adelberg's Medical Microbiology; 27th edition; Chapter 11; Spore-Forming Gram-Positive Bacilli: Bacillus and Clostridium Species
Bacillus subtilis
Bacillus stearothermophilus
Bacillus cereus
Bacillus anthracis
Bacteriology