Characteristics Shape of Pathogenic Bacteria

Morphological characteristics of pathogenic bacteria helps us to identify them, when we stain microbiological specimens and view them under microscope.

Various Shapes of Bacteria

In this blog post, i am going to share some of the distinguishing characteristics shapes of pathogenic bacteria.

  1. Vibrio choleraeComma “Curved” Shaped Gram negative rod
  2. Campylobacter:  Curved Gram negative rods that appear either comma or S shaped
  3. H. Influenzae: Small, Gram negative coccobacilli
  4. Staphylococci: Spherical, gram positive cocci arranged in irregular, grape like clusters
  5. Fig: Characteristic shape of S. aureus and V. cholerae

    Streptococci: Spherical, Gram positive cocci arranged in chains or pairs

  6. Streptococcus pneumoniae (pneumococci): Gram positive lancet-shaped cocci arranged in pairs (diplococci) or short chains.
  7. Neisseria (N. gonorrhoeae and N. meningitidis): Gram negative cocci that resemble paired kidney bean shaped
  8. Bacillus anthracis: Large, Gram positive rod with square ends, frequently found in chains
  9. Clostridium tetani: Gram positive rod with characteristics “tennis racket shaped” or “Drum stick appearance” (because of terminal spore)
  10. Clostridium perfringens: Large, Gram positive, “boxcar” shaped rods
  11. Fusobacterium spp: These pleomorphic, long Gram negative rods often with tapered “pointy” ends

    Fig: Gram Staining reaction of Fusobacterium spp

  12. Corynebacteria: Gram positive rods that appear club shaped and are arranged in palisades or in V or L shaped formations (“Chinese-Letter” appearance
  13. Listeria monocytogenes: It is a small Gram positive rods arranged in V or L shaped formations similar to corynebacteria
  14. Spirochetes (Treponema, Leptospira, and Borrelia): Thin walled, flexible, spiral rods  (Corkscrew shaped) seen only by darkfield microscope and generally not seen in standard light microscope.
  15. Borrelia: They are corkscrew shaped and are larger than the Treponema, they can be viewed under a light microscope with Giemsa or Wright stains.