Conduct experiments to study factors affecting growth of microorganisms

World of Microorganisms

1.1

World of Microorganisms

Classification of microorganisms

Bacteria Characteristic

Size	0.2 µm - 10 µm
Shape	Coccus, bacillus, spirilla, vibrio
Nutrition	Autotrophic, saprophytic, parasitic
Habitat	Air, water, soil, food, bodies of other organisms
Reproduction	Asexual: binary fission Sexual: conjugation
Example	Bacillus sp., Vibro sp.

Fungi Characteristic

Size	10 µm - 100 µm
Shape	Spherical, filamentous
Nutrition	Saprophytes, parasitic
Habitat	Places with decaying matter, faeces, animal skin and food
Reproduction	Asexual: budding, spore formation Sexual: conjugation
Example	Mushroom, yeast

Protozoa Characteristic

Size	5 µm - 250 µm
Shape	Spherical, spindle-shaped, irregular shaped
Nutrition	Saprophytic, parasitic
Habitat	Aquatic habitats, damp place, bodies of living organisms
Reproduction	Asexual: binary fission Sexual: conjugation
Example	Paramecium sp., Ameoba sp

Virus Characteristic

Size	0.02 µm - 0.4 µm
Shape	Spherical, helical, polyhedral, complex
Nutrition	-
Habitat	Lives in living host cells, forming crystals outside living cells
Reproduction	-
Example	Virus influenza A

Algae Characteristic

Size	1 µm - 100 µm
Shape	Spherical, oval-shaped, filamentous
Nutrition	Autotrophic
Habitat	Aquatic habitats, damp place
Reproduction	Asexual: binary fission, spore formation Sexual: conjugation
Example	Chlamydomonus sp. Spirogyra sp.

Factors that affect the growth of microorganisms

Factor	Explanation
Humidity	Damp conditions promote the growth and reproduction of microorganisms. In dry condition, some bacteria will form cyst or spores
Light	Microorganisms with chlorophyll prefer light condition. Fungi and few bacteria prefer dark condition. Exposure to UV light can kill microorganisms.
Temperature	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.
Nutrient	The growth rate of microorganisms depends on amount of nutrients.