Microbial community nutrition and growth

1. MICROBIAL NUTRITION
Nutrients are substances used in biosynthesis and energy release and are therefore required for
microbial growth.
Nutrients can be divided into two categories, Macronutrients and Micronutrients.
• C,O,H,N,S and P required in large amounts are the Macronutrients.
• Mn, Zn, Co, Mo,Ni and Cu are Micronutrients.
Sources of Carbon, Energy and
Electrons.
Carbon sources:
Autotrophes
Heterotrophes
CO2 sole or principal biosynthetic
carbon sources.
Reduced, performed, organic
molecules from other organisms.
Energy Source:
Phototrophs
Chemotrophs
Light
Oxidation of organic or inorganic
compounds.

2. Electron sources:
Lithotrophs
Organotrophs
Reduced inorganic molecules.
Organic molecules

3. Nutritional type Carbon source Energy source Electron source Representative
microorganism
Photolithoautotrophy CO2 Light Inorganic electron
donor.
Purple and green
sulfur bacteria,
cyanobacteria.
PhotoOrganohetrotrophy Organic carbon,
but CO2 may also
be used.
Light Organic electron
donor.
Purple non sulphur
bacteria, green non
sulphur bacteria
Chemolithoautotrophy CO2 Inorganic chemicals Inorganic electron
donor.
Sulphur oxidizing
bacteria, hydrogen
oxidizing bacteria,
methanogens,
nitrifying bacteria,
iron oxidizing
bacteria.
Chemolithoheterotrophy Organic carbon,
but CO2 may also
be used.
Inorganic chemicals Inorganic electron
donor
Some sulphur
oxidizing bacteria.

4. Major nutritional types of micro organisms
Chemoorganohetreo-
trophy
Organic Carbon. Organic
chemicals often
same as C source.
Organic electron
donor often same
as C source.
Most non
photosynthetic
microbes, including

5. Growth factors
There are three major factors:
1. Amino acids
2. Purines and pyrimidines.
3. Vitamins.
Amino acids are needed for protein synthesis; Purines and pyrimindines for nucleic acid synthesis. Vitamins
for enzyme co-factors and in very small amounts to sustain growth.
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