Media different forms

1. 20UYC101 –FUNDAMENTALS OF
MICROBIOLOGY – UNIT V –
DIFFERENT FORMS OF MEDIA
Dr. S. Sivasankara Narayani
Assistant professor
Department of Microbiology
Ayya nadar Janaki ammal college
sivakasi
28-10-2020
Dr.SS

2. UNIT - III NUTRITIONAL
REQUIREMENT AND MEDIA
PREPARATION
◦ Nutritional requirements: Nutritional types of microbes- autotrophs - phototrophs, chemotrophs -
organotrophs- lithotrophs – mixotrophs. Fastidious microorganism. Safety precautions adopted in
microbiology laboratories. *Aseptic techniques: Physical methods - chemical methods. Different forms of
media preparation: Nutrient broth – agar slope- agar deep -agar plate – semi solid - solid media. Types of
culture media: Simple- enriched- enrichment- selective- differential - transport.
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3. DIFFERENT FORMS
OF MEDIA
28-10-2020
Dr.SS

4. Nutrient broth
◦ Basically, the nutrient broth is the nutrient agar that lack of the solidifying agent, agar powder. They remain
in liquid form at room temperature and are usually used to maintain the stocks of microorganisms. In
general, they are used to grow fastidious organisms. Also, you can enrich your nutrient broth with blood,
serum, sugars… etc for special purpose.
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5. How to prepare nutrient broth?
◦ Add 13g of nutrient broth powder (CM0001B) in 1L of distilled water.
◦ Mix and dissolve them completely.
◦ Pour them into the final containers (eg. conical flask)
◦ Sterilize by autoclaving at 121°C for 15 minutes
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6. Liquid broth
◦ These media contain specific amounts of nutrients but don’t have a trace of gelling agents such as gelatin or
agar. Broth medium serves various purposes such as propagation of a large number of organisms,
fermentation studies, and various other tests. e.g. sugar fermentation tests, MR-VR broth.
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7. Agar slope
◦ Agar slants are created by bringing agar to the boiling point and pouring it into a test tube. Before the agar
cools and solidifies, the test tube is set on its side. Once the agar is cooled, the test tube can be stored
upright, and the agar inside has a slanted appearance.
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8. Agar Deep
◦ An Agar Deep Stab is a tube filled with a solid medium containing agar. It is inoculated with a needle to
observe the growth patterns in the agar. Due to the presence of agar (which slows the diffusion of oxygen
from the air), and the process of autoclaving and the presence of bacteria (both tend to deplete oxygen from
the tube), an oxygen gradient is set up in the tube such that high concentrations of oxygen are found at the
top and low to little are found at the bottom. The presence and location of growth in the tube then indicates
the oxygen requirements for any given organism.
◦
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9. Agar plate
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10. Semisolid
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11. Semi solid media
◦ Semisolid medium is prepared with agar at concentrations of 0.5% or less. Semisolid medium has a soft
custard-like consistency and is useful for the cultivation of microaerophilic bacteria or
for the determination of bacterial motility.
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12. Soild medium
◦ Solid medium contains agar at a concentration of 1.5-2.0% or some other, mostly inert solidifying agent.
Solid medium has physical structure and allows bacteria to grow in physically informative or useful ways (e.g.
as colonies or in streaks). Solid medium is useful for isolating bacteria or for determining the colony
characteristics of the isolate
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14. Clarification
28-10-2020 Dr.SS
sivasan91@gmail.com

15. Questions to think
• Different forms of media
• Use of semisolid media
• Agar deep
• Difference between solid and liquid media
• Which type of media used to isolate anaerobes
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