Morphology of Bacteria

Question 1

What are the 4 main shapes of Bacteria?

Answer 1

Spherical (Cocci/ Coccus)
Rod-Shaped (Bacilli/ Bacillus)
Spiral (Vibrio, Spirillum, Spirochete)
Branched (Myceloid)

Question 2

What does bacterial morphology refer to?

Answer 2

1) Size, shape and arrangement of bacterial
cells, as well as their cell structures, as
observed under the microscope.

2) Size, consistency, texture, shape and
colour of colonies of bacteria which are
visible to the naked eye.

Question 3

What is the general size of bacteria? Are there any exceptions?

Answer 3

Generally 1-10 microns

Mycoplasma (<0.2 microns)
Spirochaeta (500 microns)

Question 4

What are some examples of deviated Coccus?

Answer 4

Pneumococcus (Lanceolate)
Gonococcus and Meningococcus (Coffee bean)

Question 5

What are the different arrangements of Cocci?

Answer 5

Separated completely:
Micrococcus

Remain attached:
Diplococcus (1 Plane)
Streptococcus (Chain of Cocci)
Tetrads (2 Planes, 2x2)
Sarcinae (3 Planes, 2x2x2)
Staphylococcus (Clusters, Grape-shaped) Eg. Staphylococcus Aureus

Question 6

What are the different variations of Bacilli?

Answer 6

1) Long and Slender, Eg. Mycobacterium Smegmatis, Bacillus Subtilis
2) Short and Thick, Eg. Pesudomonas Aeruginosa, Escherichia Coli
3) Fusiform (Tapered ends), Club-shaped, Cocobacillus (Like Diplococcus)

Question 7

What are the different arrangements of Bacilli?

Answer 7

Complete separation:
Singles

Remain attached:
Diplobacilli (Pairs)
Streptobacilli (Chains)
Palisade Layers (Stacked along long side)
”Chinese letter” Pattern (Random)
Split-rail fence (WWW pattern)

Question 8

What are the variations in Spiral bacterial cells?

Answer 8

1) Vibrio (Comma-shaped)
2) Spirillum (Coil-shaped and Rigid)
3) Spirochete (Corkscrew-shaped and Flexible), Eg. Leptospira (Jaundice), Treponema pallidum (STI)

Variations in length, rigidity and amplitude of turns

Question 9

What are the characteristics of Myceloid?

Answer 9

Bacteria grows in the form of branching filaments (Hyphae), Eg. Actinomycetes (Produce antibiotics)

Question 10

What is Pleomorphism?

Answer 10

Describes bacteria without a distinct shape

Examples:
Propionibacterium Acnes
Haemophilus Influenzae

Question 11

What are the essential structures of a bacteria cell?

Answer 11

1) Cytoplasm
2) Ribosomes
3) Nucleoid
4) Plasma Membrane

Question 12

What are all the other Cell Structures in a Bacteria?

Answer 12

Structures external to cell wall:
1) Capsule/ Slime layer
2) Flagella
3) Axial filaments
4) Pili

5) Cell Wall

Structures within cell wall:
6) Mesosomes
7) Cell inclusions
8) Plasmid
9) Endospores