World of Microorganisms

1.1  World of Microorganisms

1. Classification of microorganisms

a) Bacteria

b) Fungi

c) Protozoa

d) Virus

e) Algae 

Size 0.2 µm - 10 µm 
Shape Coccus, bacillus, spirilla, vibrio
Nutrition Autotrophic, saprophytic, parasitic
Habitat Air, water, soil, food, bodies of other organisms
Method of reproduction

Asexual: binary fission

Sexual: conjugation

Example Bacillus sp., Vibro sp.
Size 10 µm - 100 µm
Shape Spherical, filamentous
Nutrition Saprophytes, parasitic
Habitat Places with decaying matter, faeces, animal skin and food
Method of reproduction

Asexual: budding, spore formation

Sexual: conjugation

Example Mushroom, yeast
Size 5 µm - 250 µm
Shape Spherical, spindle-shaped, irregular shaped
Nutrition Saprophytic, parasitic
Habitat Aquatic habitats, damp place, bodies of living organisms
Methode of reproduction

Asexual: binary fission

Sexual: conjugation

Example Paramecium sp., Ameoba sp.
Size 1 µm - 100 µm
Shape Spherical, oval-shaped, filamentous
Nutrition Autotrophic
Habitat Aquatic habitats, damp place
Methode of reproduction

Asexual: binary fission, spore formation

Sexual: conjugation


Chlamydomonus sp. 

Spirogyra sp.


3. Factors that affect the growth of microorganisms
Factors Explaination

Damp conditions promote the growth and reproduction of microorganisms.

In dry condition, some bacteria will form cyst or spores. 


Microorganisms with chlorophyll prefer light condition.

Fungi and few bacteria prefer dark condition.

Exposure to UV light can kill microorganisms.


Most microorganisms prefer 35 °C - 40 °C.

Low temperature in refrigerator reduce growth rate of microorganisms.

High temperature can kill microorganisms.

pH value

Optimum pH for most microorganisms is pH 7.

Some microorganism can live in environment with slightly acidic or alkaline.

Nutrients The growth rate of microorganisms depends on amount of nutrients.