Characteristics Shape of Pathogenic Bacteria

Fig: Characteristic shape of S. aureus and V. cholerae

Last updated on April 21st, 2020

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

Various Shapes of Bacteria
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 a 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
    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: Fusobacterium spp
    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 rod 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 a 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.
About Acharya Tankeshwar 467 Articles
Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. I am working as an Asst. Professor and Microbiologist at Department of Microbiology and Immunology, Patan Academy of Health Sciences, Nepal. If you want me to write about any posts that you found confusing/difficult, please mention in the comments below.