Bacterial nutrition and growth

Bacterial nutrition and growth

Importance of Microorganisms
Assistant Prof. Dr. Karreema Amine AL-Khafajii ,Babylon University, College of Medicine, Department of Microbiology.
Definition: Nutrition:
Nutrition is a process by which organisms acquire chemical substances(nutrients), used in cellular activities such as metabolism and growth. Organisms differ in the use of particular elements, their source, and chemical form.
Microbial growth
Microbial growth refers to both the increase in cell size and number of cells in a population.
Metabolism :includes all the biochemical reactions that occur in the cell.
It consists of anabolic and catabolic reactions.
Categories of essential nutrients: Macronutrients: required in relatively large quantities.e.g. proteins and carbohydrates.
Micronutrients or trace elements: required in small amounts .e.g. zinc and manganese. They are important because they are involved in enzyme functions and maintains of protein structure.
Bacteria growth
Bacteria growth by cell division; binary or transverse division. During binary fission the parent cell enlarges, duplicates its chromosomes and forms a central transverse septum that divides the cell into two daughter cells.
Generation or doubling time: the average generation time for bacteria is 30-60 minutes under optimum condition. Most pathogens such as Staphylococcus aureus and E. Coli double in 20-30 minutes. The largest generation time requires days. E.g.Mycobacterium leprae that causes leprosy doubles in 20-30 days.
The growth curve


The growth curve is a graphic representation of closed population of bacteria overtime.
This occur in four phases; lag, log (exponential), stationary, and decline phases.
1- the lag phase: in which cells adjust to new environment. There Is no change in the number of cells, but metabolic activity is high leading to increase in cellular components.