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Questions and Answers
A microbiologist needs to culture a bacterium with very specific nutrient requirements. Which type of media would be MOST suitable?
A microbiologist needs to culture a bacterium with very specific nutrient requirements. Which type of media would be MOST suitable?
- General purpose media
- Chemically defined (synthetic) media (correct)
- Selective media
- Enriched media
A researcher is trying to isolate Staphylococcus from a mixed culture. Which type of media would be MOST effective for this purpose?
A researcher is trying to isolate Staphylococcus from a mixed culture. Which type of media would be MOST effective for this purpose?
- Trypticase soy agar (TSA)
- Mannitol salt agar (correct)
- Chocolate agar
- Blood agar
Which of the following best describes the primary purpose of using a differential medium in microbiology?
Which of the following best describes the primary purpose of using a differential medium in microbiology?
- To ensure that only gram-positive bacteria can grow.
- To inhibit the growth of unwanted microorganisms.
- To distinguish between different species of microorganisms based on observable characteristics. (correct)
- To provide a wide range of nutrients for diverse microbial growth.
A microbiologist observes a bacterial culture in a broth tube exhibiting a thick layer of growth at the top surface. How should this growth pattern be described?
A microbiologist observes a bacterial culture in a broth tube exhibiting a thick layer of growth at the top surface. How should this growth pattern be described?
In the Five I's of microbiology, which step involves placing a sample into a sterile medium to facilitate growth?
In the Five I's of microbiology, which step involves placing a sample into a sterile medium to facilitate growth?
A clinical lab is testing a new disinfectant. They grow bacteria on a set of agar plates, treat them with the disinfectant, and then incubate them to observe any growth inhibition. Which of the Five I's does observing growth inhibition represent?
A clinical lab is testing a new disinfectant. They grow bacteria on a set of agar plates, treat them with the disinfectant, and then incubate them to observe any growth inhibition. Which of the Five I's does observing growth inhibition represent?
A microbiologist is trying to identify an unknown bacterium. They perform a Gram stain, observe cell morphology under a microscope, and conduct various biochemical tests. Which aspect of microbial analysis do all these techniques fall under?
A microbiologist is trying to identify an unknown bacterium. They perform a Gram stain, observe cell morphology under a microscope, and conduct various biochemical tests. Which aspect of microbial analysis do all these techniques fall under?
A researcher is working with Mycobacterium leprae. Which of the following methods would be MOST appropriate for culturing this particular bacterium?
A researcher is working with Mycobacterium leprae. Which of the following methods would be MOST appropriate for culturing this particular bacterium?
Why is temperature control during the incubation phase of microbial culture so important?
Why is temperature control during the incubation phase of microbial culture so important?
A microbiologist uses a spread plate technique to quantify bacteria in a sample. What key characteristic of this technique allows for accurate bacterial counts?
A microbiologist uses a spread plate technique to quantify bacteria in a sample. What key characteristic of this technique allows for accurate bacterial counts?
Flashcards
Liquid Media (Broth)
Liquid Media (Broth)
Water-based solutions used to grow microbes.
Semisolid Media
Semisolid Media
Microbial media that clots at room temperature.
Solid Media
Solid Media
Microbial media that is solid at room temperature but liquifies when heated to boiling.
Chemically Defined (Synthetic) Media
Chemically Defined (Synthetic) Media
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Complex Media (Nonsynthetic)
Complex Media (Nonsynthetic)
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General Purpose Media
General Purpose Media
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Enriched Media
Enriched Media
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Selective Media
Selective Media
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Differential Media
Differential Media
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Spread Plate
Spread Plate
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Study Notes
- Media can be classified based on physical state, chemical composition, and function.
Physical State of Media
- Liquid media (broths) are water-based solutions.
- Semisolid media clot at room temperature.
- Solid media are solid at room temperature but liquefy at the boiling temperature of water.
Chemical Composition of Media
- Chemically defined (synthetic) media contain pure compounds with an exact chemical formula.
- Complex media (nonsynthetic) contain components that are not chemically defined and cannot be represented by an exact chemical formula.
Functional Types of Media
- General purpose media support microbes without special growth requirements, such as nutrient agar and trypticase soy agar (TSA).
- Enriched media contain complex organic substances like blood, for example blood agar which detects hemolysins production and chocolate agar for respiratory bacteria, and Thayer-Martin agar for Neisseria.
- Selective media contain agents that inhibit certain microbes, favoring the growth of others, like phenylethyl alcohol agar, which is selective for gram-positive bacteria and inhibits gram-negative bacteria.
- Differential media include MacConkey agar, being both selective and differential, it contains neutral red, which turns red under acidic conditions produced by lactose-fermenting bacteria like E. coli; Salmonella, a non-lactose fermenter, can also grow on it.
- Differential media also include Mannitol salt agar, which is also selective and differential: its 7.5% NaCl inhibits most organisms except staphylococcus, because it can withstand high salt.
- Live media, host animals are required for certain bacteria to grow, an example being Mycobacterium leprae on mice footpads.
Basic Procedures to Examine & Characterize Microbes (The Five I’s)
- The five I's are inoculation, incubation, isolation, inspection, and identification.
- Inoculation involves introducing a sample into a medium.
- Incubation occurs in an incubator at temperatures generally between 20°C and 40°C.
- Isolation, spread plates are used to quantify bacteria in a solution such that colonies are evenly distributed and easily counted.
- Inspection involves macroscopic observation of colonies; bacterial growth patterns in broths include a pellicle (thick growth at the top), sediment at the bottom, or turbid growth throughout.
- Identification is determining the type of microbe using morphological, physiological, and biochemical characteristics.
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Description
Classification of media based on physical state: liquid, semi-solid, solid. Chemical composition: chemically defined, complex. Functional types: general purpose, enriched, selective.
