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2. Lecture by
Dr. Muhammad Sajjad
Nutritional Requirement of Microorganisms
&
Bacterial Growth

3. All organisms require a source of energy. Some rely on
chemical compounds (chemotrophs), Others utilize
radiant energy (sunlight) (phototrophs)
Q: Enlist Nutritional Requirements of Microorganisms?
•There are Two categories of essential nutrients:
i) Macronutrients:
ii) Micronutrients:

5. i) Macronutrients:
• Required in large quantities.
• Play principal roles in cell structure and
metabolism.
• Includes: Caron, Oxygen, Hydrogen, Nitrogen,
Sulfur, Phosphorus (components of carbohydrates,
lipids, Proteins & nucleic acid)
• Potassium, calcium, magnesium & iron (Part of
enzymes & cofactor) for normal growth.

6. ii) Micronutrients:
•Require in small amount.
•Essential for activity of certain enzymes, usually as
cofactor. Includes: Iron, Zinc, Copper, molybdenum
(Mo6+) referred to as Trace Elements.
•vitamins and vitamin like compounds, function either
as coenzymes or building blocks for coenzymes.
•All living organisms require water, and in the case of
bacteria all nutrients must be in aqueous solution
before they can enter the cells.

8. Q: Classification Based on Nutrition Continue….
• Autotrophs: Require CO2 as their major source of carbon.
• Heterotrophs: Require organic compounds as a source of carbon.
• Phototrophs: Bacteria which derive their energy from sunlight
• Chemotrophs: Bacteria which derive their energy from chemical
compounds.
• Lithotrophs; use inorganic source of Hydrogen (electrons) for their
metabolism like NH3, H2S etc.
• Organotrophs: use organic source of Hydrogen (electrons) for their
metabolism.

9. Bacterial Growth

10. GROWTH CYCLE
•Bacteria reproduce by binary fission, a process by which one
parent cell divides to form two progeny cells.
•The doubling (generation) time of bacteria ranges from as
little as 20 minutes for Escherichia coli to as long as 18 hours
for Mycobacterium tuberculosis.

11. Q: Describe the bacterial growth cycle with diagram:
Growth cycle consists of four phases:
•(1) The first is the lag phase, during which vigorous
metabolic activity occurs but cells do not divide. This
can last for a few minutes up to many hours.
•(2) The log (logarithmic) phase is when rapid cell
division occurs. Also known as exponential phase.

12. (3) The stationary phase occurs when nutrient depletion
or toxic products cause growth to slow until the
number of new cells produced balances the number of
cells that die, resulting in a steady state.
(4) The final phase is the death phase, which is marked
by a decline in the number of viable bacteria.

14. Q: Some bacteria are obligate anaerobes. Which of the following
statements best explains this phenomenon?
(A) They can produce energy both by fermentation and by
respiration using the Krebs cycle and cytochromes.
(B) They cannot produce their own ATP.
(C) They do not form spores.
(D) They lack Superoxide dismutase and Catalase
(E) They do not have a capsule.

15. Thank You