Microbial culturing and growth
Discipline Courses-I
Semester-I
Paper: Phycology and Microbiology
Unit-I
Lesson: Bacterial Culturing techniques
Lesson Developer: Richa Sharma
College/Department: Microbiology, University of Delhi
Institute of Lifelong Learning, University of Delhi
, Microbial culturing and growth
Table of Contents
Chapter: Microbial culturing and growth
Microbial culturing
Why do we culture microbes?
How to culture microbes?
Culture media
Pure cultures
Streak plate method
Spread plate method
Pour plate method
Culture maintenance
Culture collections
How to distinguish between microbes morphologically?
Are all microbes culturable?
Microbial Growth
Requirements for growth
Nutritional factors
Physical factors
Study of growth
Phases of growth
Measurements of growth
Summary
Exercise/ Practice
Glossary
References/ Bibliography/ Further Reading
Institute of Lifelong Learning, University of Delhi 1
, Microbial culturing and growth
Microbial Culturing
“Culturing” microbes means propagating and maintaining micro-organisms. In this
section we will study why, how and under what conditions should we culture micro-
organisms?
Why do we culture microbes?
Micro-organisms play vital role in various aspects of our life. Besides being an inherent
part of our system (human microflora), micro-organisms find applications in almost every
sector ranging from industrial, food, and pharmaceutical to environmental. Micro-
organisms aid in the manufacture of industrially important products, food products and
recycle of substances etc. The other side of the coin, however, is that a tiny but
significant proportion of micro-organisms cause human diseases. Other detrimental
effects of microbes include food spoilage, biodeterioration etc.
Both these positive as well as negative implications of microbes are very important and
need to be studied in detail. The basic tool for studying microbes is by their ‘culturing’.
The preliminary step before we can study any aspect of microbial growth, physiology or
application, we need to first culture (grow) them, therefore microbial culturing becomes
the first and most important technique in microbiology. Microbial cultures are used to
determine the type of organism and its abundance.
How to culture microbes?
In this section we will learn about the requirements and techniques used for culturing
microbes. Pre-requisite for the growth of a microbe is a “culture medium” which is a
source of nutrients required for the growth and maintenance of the micro-organism.
Culture media
Types of media
I. Based on the composition of the medium, it can be of two types:
1. Complex/ Chemically undefined media
Institute of Lifelong Learning, University of Delhi 2
, Microbial culturing and growth
It is referred to as ‘complex’ because the exact components and their quantity is not
defined. It consists of complex raw materials mainly plant and animal hydrolysates such
as peptone, soyabean extract, beef extract and meat extract.
Complex media is used for routine cultivation of micro-organisms. Example of the most
commonly used complex medium is nutrient broth/ nutrient agar.
Table : Composition of complex medium
Source: Author
Nutrient Broth Quantity Nutrients supplied
Beef extract 3.0 g Vitamins, minerals
Peptone 5.0 g Amino acids, peptides
Water 1L
2. Synthetic/ Chemically defined media
In this medium, the exact chemical composition and quantity of each constituent is
known. Synthetic medium is used for determining the nutritional requirements of
heterotrophs.
Table : Composition of synthetic medium
Source: Author
Synthetic broth medium Quantity Nutrients supplied
Glucose 5.0 g Simple sugar
Ammonium phosphate 1.0 g Nitrogen, phosphate
Sodium chloride 5.0 g Sodium and chloride ions
Magnesium sulfate 0.2 g Magnesium ions, sulfur
Potassium phosphate 1.0 g Potassium ions, phosphate
Water 1.0 L
Institute of Lifelong Learning, University of Delhi 3
Discipline Courses-I
Semester-I
Paper: Phycology and Microbiology
Unit-I
Lesson: Bacterial Culturing techniques
Lesson Developer: Richa Sharma
College/Department: Microbiology, University of Delhi
Institute of Lifelong Learning, University of Delhi
, Microbial culturing and growth
Table of Contents
Chapter: Microbial culturing and growth
Microbial culturing
Why do we culture microbes?
How to culture microbes?
Culture media
Pure cultures
Streak plate method
Spread plate method
Pour plate method
Culture maintenance
Culture collections
How to distinguish between microbes morphologically?
Are all microbes culturable?
Microbial Growth
Requirements for growth
Nutritional factors
Physical factors
Study of growth
Phases of growth
Measurements of growth
Summary
Exercise/ Practice
Glossary
References/ Bibliography/ Further Reading
Institute of Lifelong Learning, University of Delhi 1
, Microbial culturing and growth
Microbial Culturing
“Culturing” microbes means propagating and maintaining micro-organisms. In this
section we will study why, how and under what conditions should we culture micro-
organisms?
Why do we culture microbes?
Micro-organisms play vital role in various aspects of our life. Besides being an inherent
part of our system (human microflora), micro-organisms find applications in almost every
sector ranging from industrial, food, and pharmaceutical to environmental. Micro-
organisms aid in the manufacture of industrially important products, food products and
recycle of substances etc. The other side of the coin, however, is that a tiny but
significant proportion of micro-organisms cause human diseases. Other detrimental
effects of microbes include food spoilage, biodeterioration etc.
Both these positive as well as negative implications of microbes are very important and
need to be studied in detail. The basic tool for studying microbes is by their ‘culturing’.
The preliminary step before we can study any aspect of microbial growth, physiology or
application, we need to first culture (grow) them, therefore microbial culturing becomes
the first and most important technique in microbiology. Microbial cultures are used to
determine the type of organism and its abundance.
How to culture microbes?
In this section we will learn about the requirements and techniques used for culturing
microbes. Pre-requisite for the growth of a microbe is a “culture medium” which is a
source of nutrients required for the growth and maintenance of the micro-organism.
Culture media
Types of media
I. Based on the composition of the medium, it can be of two types:
1. Complex/ Chemically undefined media
Institute of Lifelong Learning, University of Delhi 2
, Microbial culturing and growth
It is referred to as ‘complex’ because the exact components and their quantity is not
defined. It consists of complex raw materials mainly plant and animal hydrolysates such
as peptone, soyabean extract, beef extract and meat extract.
Complex media is used for routine cultivation of micro-organisms. Example of the most
commonly used complex medium is nutrient broth/ nutrient agar.
Table : Composition of complex medium
Source: Author
Nutrient Broth Quantity Nutrients supplied
Beef extract 3.0 g Vitamins, minerals
Peptone 5.0 g Amino acids, peptides
Water 1L
2. Synthetic/ Chemically defined media
In this medium, the exact chemical composition and quantity of each constituent is
known. Synthetic medium is used for determining the nutritional requirements of
heterotrophs.
Table : Composition of synthetic medium
Source: Author
Synthetic broth medium Quantity Nutrients supplied
Glucose 5.0 g Simple sugar
Ammonium phosphate 1.0 g Nitrogen, phosphate
Sodium chloride 5.0 g Sodium and chloride ions
Magnesium sulfate 0.2 g Magnesium ions, sulfur
Potassium phosphate 1.0 g Potassium ions, phosphate
Water 1.0 L
Institute of Lifelong Learning, University of Delhi 3
