1.
SERIAL DILUTION TECHNIQUE
M.J. Afra
UG Scholar
Department of Microbiology
Thassim Beevi Abdul Kader College
For Women Kilakarai

2.
AIM
• To know the microbial population of the given
sample
• To study the number of microorganisms present
in the environment
• To dilute the sample to get countable number of
colonies
• To understand the serial dilution technique

3.
INTRODUCTION
• The microbial population in our environment is large
and complex
• Microbes are isolated from various substrates and
sources
• Organisms are isolated from various places by using
culture media
• To study the number of microorganisms present in the
environment/qualitative analysis of microbial samples
• Colony means group of cells that are emerged from a
single cell by continuous transverse fission within the
prescribed time
• To avoid few types of problems microbiologists perform
serial dilution technique to count the colonies

4.
DILUTION SCHEME
• One part of the sample is mixed with one part of
diluent, the result will be 1:2 dilution
• One part of sample is placed on nine parts of
diluent, the result will be 1:10 dilution
• One part of the 1:10 dilution was transferred to 9ml
of diluent results in additional one to ten dilution
Volume of sample
Dilution = --------------------------------------
Total volume of sample and diluent

5.
MATERIALS REQUIRED
• 9ml water blanks in sterile test tubes
• Test tubes
• Pipettes
• Cotton
• Nutrient agar
• Potato dextrose agar
• Petri plates
• Markers
• Sample

6.
PROCEDURE
1) SAMPLE:
Sterile samples were collected from the
environment, plants, animals or humans
2) STOCK PREPARATION
SOLID – 10g of sample taken and grinded by using
mechanical blender and suspended in 100ml of
diluent
LIQUID – 1ml is suspended in 9ml of water

7.
PROCEDURE
3) DILUENT PREPARATION:
Arrange the tubes in a rack
Fill the tubes with 9ml of distilled water or saline
Insert cotton plug to all test tubes
Sterilize the test tubes for 15 minutes under 121oC
Keep the tubes ready for serial dilution

8.
PROCEDURE
• The agar were calculated, mixed and sterilized
for 15 minutes under 121o C
• The glasswares were sterilized
• Work bench of laminar air flow chamber was
cleaned using disinfectant followed by UV lamp
for 15 minutes before working

9.
PROCEDURE (serial dilution)
• Keep ready and arrange all materials required for the
dilution in laminar air flow chamber
• Arrange test tubes and label them (10-1, 10-2, …… , 10-10)
• Add 1ml of the sample from the diluent
• Makeup further dilution upto 10-8
• Perform plating from the appropriate dilution by pour
plate method
• Add 1ml of diluted sample to appropriately labelled petri
plates after dilution
• Pour 15ml -20ml of media to the petri plates
• Incubate all the plates at appropriate temperature and
observe the colonies

10.
No of colonies * dilution factor
No of colonies (per gram) = -----------------------------------------
Dry weight of the sample

11.
THANK YOU
M.J. Afra
UG Scholar
Department of Microbiology
Thassim Beevi Abdul Kader College
For Women Kilakarai