Escherichia coli appears as rod-shaped bacteria under the microscope, which classifies it as Bacillus. This shape is significant because it influences bacterial growth patterns and motility. Understanding the morphology helps in identifying the organism during Gram staining and guides appropriate antimicrobial treatment. Unlike cocci, which are spherical, or spirilla and vibrios, which have spiral or curved shapes, E. coli’s rod shape aids in clinical diagnosis of infections caused by Enterobacteriaceae family members.

Reference: Medical Microbiology, Jawetz, Melnick & Adelberg, 28th Edition.