This document describes the different shapes and arrangements of bacteria. It outlines the main shapes as cocci (spherical or oval), bacilli (rod-shaped), vibrios (comma-shaped curved rods), spirilla (spiral forms), spirochetes (flexuous spiral forms), and actinomycetes (branching filamentous forms). It also discusses mycoplasmas, which lack a cell wall. Additionally, it discusses characteristic cellular arrangements of bacteria, such as diplococci, streptococci, tetrads, sarcina, and streptobacilli. The type of arrangement depends on the plane of cell division and whether daughter cells remain attached.

1. SHAPE OF BACTERIA
V.S.RASHMI PRIYEM
ULTRA’S BEST DENTAL SCIENCE COLLEGE, MADURAI

2. COCCI
 Spherical or Oval Cells.
G +ve G -ve

3. BACILLI
 Rod-Shaped Cells.
G -veG +ve

4. VIBRIOS
 Comma-Shaped, Curved Rods.
 Derive their Name from their Characteristic
Vibratory Motility.

5. SPIRILLA
 Rigid Spiral Forms.

6. SPIROCHETES
 Flexuous Spiral Forms.

7. ACTINOMYCETES
 Branching Filamentous Bacteria.
 Because of a Fancied Resemblance to the
Radiating Rays of the Sun when seen in Tissue
Lesions.

8. MYCOPLASMAS
 Bacteria that are Cell Wall Deficient.
 Hence Do Not Possess Stable Morphology.
 They Occur as Round or Oval Bodies and as Interlacing Filaments.
 When Cell Wall Synthesis becomes Defective, either Spontaneously or
as a Result of Drugs like Penicillin, Bacteria Lose their Distinctive
Shape.
 Such Cells are called Protoplasts, Spheroplasts or L Forms.

9. CELLULAR ARRANGEMENT
 Bacteria sometimes show Characteristic Cellular Arrangement or
Grouping.
 Cocci may be Arranged in Pairs (Diplococci), Chains(Streptococci), Groups
of Four (Tetrads) or Eight (Sarcina), or as Grape-like Clusters
(Staphylococci).
 Bacilli may be Arranged in Chains (Streptobacilli), Others are Arranged at
Angles to Each Other, presenting a Cuneiform or Chinese Letter Pattern
(Corynebacteria).

10. DIPLOCOCCI

11. STREPTOCOCCI

12. TETRADS

13. SARCINA

14. STAPHYLOCOCCI

15. STREPTOBACILLI

16. CUNEIFORM OR CHINESE LETTER
PATTERN (CORYNEBACTERIA)

17. CELLULAR ARRANGEMENT
 The Type of Cellular Arrangement is Determined by the
Plane through which Binary Fission Takes Place and by the
Tendency of the Daughter Cells to Remain Attached Even
After Division.