17 Questions
What is the purpose of using culture media in microbiology?
To study the characteristics of microorganisms
What is the function of peptone in culture media?
To partially digest proteins and supply carbon & nitrogen
Which of the following is NOT a nutrient required for microbial growth?
Vitamin source
What is the role of agar in microbiological media?
Solidifies the media and is not digested by bacteria
What temperature range does agar melt and solidify at?
Melts at 80-90°C, solidifies at 35-42°C
Which growth factor is specifically mentioned for E.coli and Salmonella typhi in the text?
Arginine for E.coli and Tryptophan for Salmonella typhi
What is the agar concentration range in solid media?
1.5-2.5%
Which type of media is used for observing bacterial motility?
Semi-solid media
What is the distinguishing feature of enriched media?
Has extra nutrients like blood or serum
Which type of culture media is composed of both natural and synthetic substances?
Semi-synthetic medium
In which type of culture media are all components and their concentrations known?
Artificial media
Which type of media supports most non-fastidious bacteria?
General purpose media
What is the main purpose of selective media in microbiology?
Allowing the growth of certain organisms while inhibiting others
Which type of media is specifically used for isolating a particular genus of bacteria?
Specialized media
How does differential media aid in visual differentiation of bacteria?
By adding substrates and indicators to create visual differences in bacterial colonies
In microbiology, what is the primary function of assay media?
To conduct sensitivity tests such as antibiotic or amino acid tests
Which agar type is known for differentiating E.coli and Salmonella based on lactose fermentation?
MacConkey agar
Study Notes
Culture Media or Nutrient Media
- Culture media is the food material or substances required for growing microorganisms in vitro (outside the body)
- Uses of culture media:
- To identify the cause of infection from clinical samples
- To study the characteristics or properties of microorganisms
- To prepare biological products like vaccines, toxoids, and antigens
Components of Culture Media
- Nutrients:
- Energy source
- Carbon source
- Nitrogen source
- Mineral salts:
- Sulphates, phosphates, chlorides, and carbonates of K, Mg, and Ca
- pH: 7.2-7.4
- Growth factors:
- Arginine for E. coli
- Tryptophan for Salmonella typhi
- Peptone:
- Partially digested protein with hydrolytic enzymes (pepsin, trypsin)
- Supplies carbon and nitrogen to the media
- Agar:
- Heteropolysaccharides extracted from certain sea red algae
- Used as a solidifying agent in many microbiological media
- Melts at 80-90°C and solidifies at 35-42°C
- Not digestible by any pathogenic bacteria
Classification of Culture Media
Based on Consistency
- Solid media:
- Contain 1.5-2.5% agar
- Useful for the isolation, colony characteristic, and identification of bacteria
- Examples: Nutrient agar, MacConkey agar
- Semi-solid media:
- Contain 0.3-0.5% agar
- For the observation of bacterial motility and preservation of bacteria
- Examples: Manitol
- Liquid or broth media:
- Without agar
- For the proliferation of bacteria (activation of microorganisms)
- Examples: Nutrient broth, MacConkey broth
Based on Chemical Components
- Natural medium:
- Composed of natural products
- Chemical compositions are unknown
- Examples: Urine, milk, vegetable, blood
- Semi-synthetic medium:
- Composed of natural and synthetic substances
- Examples: PDA (Potato Dextrose Agar)
- Artificial or synthetic media:
- All components and their concentrations are known
- Examples: MacConkey agar
Based on Functional Aspect
- General purpose media (Basal media or ordinary media):
- Support most non-fastidious bacteria
- Examples: Peptone water, nutrient broth, and nutrient agar
- Enriched media:
- Addition of extra nutrients to basal medium
- Used to grow fastidious bacteria
- Examples: Blood agar, chocolate agar
- Selective media:
- Allow the growth of certain type of organisms, while inhibiting the growth of other organisms
- Examples: Salmonella-Shigella Agar (SSA)
- Differential media:
- Special substrates and indicators are added to produce a visual differentiation
- Examples: MacConkey agar, Eosin Methylene Blue (EMB) agar
- Specialized media:
- Used for isolation of specific genus of bacteria
- Examples: TCBS (Thiosulphate Citrate Bile salt Sucrose) Agar for isolation Vibrio cholera
- Assay media:
- Used for sensitivity test (antibiotic, amino acid, vitamins)
- Examples: Mueller Hinton Agar
Learn about the types and uses of culture media in microbiology, including nutrient media for growing microorganisms in vitro. Explore how culture media is utilized to identify infections, study microorganism characteristics, and perform research in the field of microbiology.
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