This document discusses the various shapes, sizes, and arrangements of microbial cells. It notes that bacteria sizes range from 0.1 to 60 micrometers, and that their shapes include spherical (cocci), rods (bacilli), spirals, and other irregular shapes. The arrangement of cocci is more complex than bacilli, depending on how the cells adhere after division. Common coccus arrangements include diplococci, streptococci, tetracocci, and staphylococci. Bacilli typically divide across their short axis into mono-bacilli, diplobacilli, or streptobacilli. Spirilla can take vibroid or helical shapes. Other microbial cell types include pleomorphic

1. Prepared by : Dr Misbah Ajaz
Dept of Microbiology,BGSBU,Rajouri

2.  Size, shape and arrangement of
microbial cells vary with species
 Bacteria are of about 0.1 to 60 × 6 µm in
size
 Bacilli =5 × 0.4-0.7 µm,
 Pseudomonads =0.4-0.7 µm diameter, 2-
3 µm length)
 Micrococci =about 0.5µm diameter

4.  Generally, the bacterial cells are spherical
(coccus, plural cocci which mean berries)
 Elongated rods (Bacillus, plural bacilli), helical
rods (Spirillum, plural spirilli)
 Pear-shaped (Pasteurid), lobed spheres (Sulf
 olobus), rods with squared ends (Bacillus
anthracis)
 Rods with helically sculptured surface (Seliberid)
and of changing shape (pleomorphic), etc.
 Unicellular cyanobacterial cells are usually
spherical (Chroococcus, Scenedesmus, Anacystis)
 Some are elongated and multicellular.

5.  Arrangement of cells is more complex in cocci
than bacilli.
 The arrangement of cells depends upon
adherence of cells together after the cell
division

6. COCCUS FORMS:
 Diplococcus

 Streptococcus
 Tetracocci
 Straphylococci
 Sarcinae:
BACILLUS FORMS
 Mono-bacillus
 Diplobacillus
 Streptobacillus
 Coccobacillus

7. FORMS OF SPIRILLI
 Vibrioid
 Helical
OTHER FORMS
 Pleomorphic
 Trichomes
 Palisade
 Hyphae

8. There are several groups of cocci based on the
number and arrangement of cells.
(a) Diplococcus:
 Cells divide in one plane and get attached
permanently in pairs.
(b) Streptococcus:
 Cells divide in one plane and remain attached
to form a linear chain of cells.
i) Coccus Form

9. (c)Tetracocci:
 Cells divide in two planes and form groups of
four cells.
(d) Straphylococci:
 Cells divide in three planes in an irregular
pattern producing bunches of cocci.
(e) Sarcinae:
 Cells divide in three planes in regular pattern
producing bunches of cocci.

10. There are a few groups of bacilli unlike cocci as the former divide
across their short aries.
(a) Mono-bacillus:
 The single elongated cells freely present in nature are mono-
bacillus.
(b) Diplobacillus:
 After division the cells remain adhered and appear in paired form.
(c) Streptobacillus:
 After division the cells remain attached in chains appearing like
straws.
(d) Coccobacillus:
 The oval cells looking like cocci are called coccobacilli
 There is two meaning of bacillus, one is the form and the second is
the genus. For example the bacterium Bacillus anthracis causes
anthrax disease.

11. (a) Vibrioid:
 Bacterial cells having less than one complete
twist form vibrioid shape e.g. Vibrio cholerae.
(b) Helical:
 Cells that have more than one twist form a
distinct helical shape e.g. Spirillum (with
flagella).

12. (a) Pleomorphic:
 Of changing forms e.g. Rhizobium, Mycoplasma,
etc.
(b) Trichomes:
 Cells divide in one plane forming a chain which
has much larger area of contact between the
adjacent cells e.g. Baggiatoa, Saprospria.
(c) Palisade:
 The cells are arranged laterally (side by side) to
form a match sticks like structure and at angles to
one another e.g. Corynebacterimn diphtheriae.

13. (d) Hyphae:
 Some microorganisms form the multicellular, thin-walled,
profusely branched filaments called hyphae. The
interwoven hyphae are collectively known as mycelium e.g.
Streptomyces, Aspergillus, and Penicillium. The
cyanobacterial cells are comparatively larger than the
bacterial cells.
 In addition, the cell size of eukaryotes such as algae, fungi,
protozoa, etc. is several times greater than the cells of
prokaryotes. The unicellular Cyanobacteria are usually
spherical or elongated. The fungi are either unicellular
(yeast, Candida) or multicellular hyphal (Fusarium,
Aspergillus) forms.

17. Thank you