Page 50 - MNU microbiology theoritical 2025

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

Requirements for microbial growth

1- Nutritional requirements

2- Environmental requirements

I) Nutrient requirements

Growth of any prokaryote depends not only on a suitable physical environment,

but also on the availability of nutrients.

Microorganisms require elements in large quantities (Macronutrients), and several

other elements are needed in very small amounts (Macronutrients).

A- Macronutrients

• Microorganisms require about ten elements in large quantities, because they are

used to construct carbohydrates, lipids, proteins, and nucleic acids.

• 95% or more of cell dry weight is made up of a few major elements: carbon,

oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, calcium, magnesium

and iron.

B- Trace Elements

• Microbes require very small amounts of other

mineral elements, such as copper, molybdenum, and zinc; these are referred to

as trace elements. Most are essential for the activity of certain enzymes, usually

as cofactors.

General Microbiology & Immunology (PM 401) theoretical handbook Page 39