Page 51 - MNU microbiology theoritical 2025

General Microbiology & Immunology (PM 401) Second level Semester 4 2024/2025

C- Growth Factors

(1) Amino acids: Amino acids are needed for protein synthesis.

(2) Purines and pyrimidines: Purines and pyrimidines for nucleic acid synthesis.

(3) Vitamins: make up all or part of enzyme cofactors, and only very small

amounts are required for growth

Nutritional Classification of Bacteria

I- According to carbon sources

1- Autotrophs

• Organisms that obtain carbon from carbon dioxide and use light energy

or inorganic chemical compounds to produce complex organic

compounds are known as autotrophs.

• These are bacteria that can synthesize their own food from inorganic

compounds.

Autotrophic bacteria are further classified into two:

Organism that uses CO2 as their sole source of carbon. (self feeders)

2- Heterotrophs

Organism that uses preformed organic molecules from other organisms as
their carbon source (other eaters)

II- According to Energy sources

1- Phototrophs

Organisms that utilize light is the main energy source (light eaters)
2- Chemotrophs

Organisms obtain energy from oxidation of organic or inorganic

compounds (chemical eaters)

General Microbiology & Immunology (PM 401) theoretical handbook Page 40