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Questions and Answers
What is a microbial culture?
What is a microbial culture?
- A method of multiplying microorganisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. (correct)
- A technique to identify different species of plants.
- A method to create new species of bacteria.
- A process of decomposing organic materials.
What is the purpose of culturing bacteria?
What is the purpose of culturing bacteria?
- To change the pH of soil.
- To isolate bacteria. (correct)
- To enhance genetic diversity in plants.
- To increase bacterial mutations.
Which of the following is not a property of culturing bacteria?
Which of the following is not a property of culturing bacteria?
- Increase microbial resistance. (correct)
- Test for antibiotic sensitivity.
- Estimate viable counts.
- Create antigens for laboratory use.
What should a culture medium provide for the growth of bacteria?
What should a culture medium provide for the growth of bacteria?
Why should the pH of the culture medium be similar to that of tissues and body fluids?
Why should the pH of the culture medium be similar to that of tissues and body fluids?
What are differential media designed to recognize?
What are differential media designed to recognize?
What type of hemolysis results in a clear area around colonies?
What type of hemolysis results in a clear area around colonies?
Which type of hemolysis is demonstrated by Streptococcus pneumonia?
Which type of hemolysis is demonstrated by Streptococcus pneumonia?
What percentage of blood is typically found in blood agar?
What percentage of blood is typically found in blood agar?
Which bacterial enzyme is responsible for lysing red blood cells in blood agar?
Which bacterial enzyme is responsible for lysing red blood cells in blood agar?
Which bacterium displays gamma-hemolysis?
Which bacterium displays gamma-hemolysis?
Which type of media supports the growth of most non-fastidious bacteria?
Which type of media supports the growth of most non-fastidious bacteria?
Which of the following is an example of enriched media?
Which of the following is an example of enriched media?
What additional components are included in enriched media compared to basal media?
What additional components are included in enriched media compared to basal media?
Which type of media is designed to inhibit the growth of unwanted commensal bacteria?
Which type of media is designed to inhibit the growth of unwanted commensal bacteria?
Which example below is not a type of basal media?
Which example below is not a type of basal media?
What agent might not be used to make selective media?
What agent might not be used to make selective media?
Which type of media is referred to as 'broths'?
Which type of media is referred to as 'broths'?
What is a use for solid media?
What is a use for solid media?
What solidifying agent is used to convert a liquid medium to a solid medium?
What solidifying agent is used to convert a liquid medium to a solid medium?
What is reduced to 0.2-0.5% to render a medium semisolid?
What is reduced to 0.2-0.5% to render a medium semisolid?
Why can't the colony morphology of bacteria be seen in liquid media?
Why can't the colony morphology of bacteria be seen in liquid media?
Semi-solid media are used primarily for which purpose?
Semi-solid media are used primarily for which purpose?
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Study Notes
Types of Culture Media
- Simple Media: Support growth of most non-fastidious bacteria, e.g. peptone water, nutrient broth, and nutrient agar.
- Complex Media: Enriched with extra nutrients like blood, serum, or egg yolk, e.g. blood agar and chocolate agar, used for fastidious bacteria.
Classification by Functional Use
- Basal Media: Simple media that support most non-fastidious bacteria.
- Enriched Media: Basal media with extra nutrients, enabling growth of fastidious bacteria.
- Selective Media: Designed to favor growth of target organisms, inhibiting unwanted bacteria, e.g. MacConkey agar and Thiosulphate Citrate Bile salt Sucrose agar.
Cultivation
- Microbial Culture: Method of multiplying microorganisms in predetermined culture media under controlled laboratory conditions.
- Purpose of Culturing: Isolation of bacteria, estimating viable counts, testing antibiotic sensitivity, and creating antigens for laboratory use.
Culture Media by Consistency
- Liquid Media: Broths, e.g. nutrient broth, used for propagating large numbers of microorganisms, fermentations studies, and biochemical tests.
- Solid Media: Converted from liquid media by adding solidifying agents like agar-agar, used for surface growth, pure culture isolations, storage, and observing biochemical reactions.
- Semi-Solid Media: Used for fermentation studies and determining bacterial motility.
Differential Media or Indicator Media
- Differential Media: Designed to recognize different bacteria based on colony color, e.g. MacConkey agar and Thiosulphate Citrate.
- Blood Agar: A differential medium containing 5-10% sheep, horse, or rabbit blood, used to distinguish pathogenic bacteria based on hemolysins.
Hemolysis on Blood Agar
- Beta Hemolysis (β-Hemolysis): Complete lysis of red blood cells, resulting in a clear area around colonies, e.g. Streptococcus pyogenic.
- Alpha Hemolysis (α-Hemolysis): Partial lysis of RBCs, resulting in greenish discoloration around colonies, e.g. Streptococcus pneumonia.
- Gamma-Hemolysis (γ-Hemolysis): No lysis of RBCs, typical of Enterococcus faecalis.
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