13 Questions
Which type of media favors the growth of particular microorganisms?
Selective media
What distinguishes hemolytic and nonhemolytic bacteria on blood agar?
Clear zones around colonies
Which agar is used to isolate staphylococci from clinical and nonclinical samples?
Mannitol salt agar
What do selective media like bile salts or dyes like basic fuchsin and crystal violet favor the growth of?
Gram-negative bacteria
What do differential media distinguish between?
Different groups of bacteria
Which type of agar is both a differential medium and an enriched medium?
Blood agar
Which type of bacteria does MacConkey agar selectively isolate and differentiate based on lactose fermentation?
Gram-negative bacteria
What color do lactose fermenters turn on MacConkey agar?
Red or pink
What is the function of blood agar when it comes to the red blood cells incorporated into the medium?
It classifies bacteria based on their effect on red blood cells
What is the differential function of blood agar?
To classify bacteria based on their effect on red blood cells
What differentiates Staphylococcus aureus from S. epidermidis on Mannitol salt agar?
Formation of yellow zones
What is the role of Eosin methylene blue (EMB) agar in detecting E. coli and related bacteria?
Differentiates between gram-negative bacteria
What is the purpose of the dyes eosin and methylene blue in Eosin methylene blue (EMB) agar?
To differentiate between gram-negative bacteria
Study Notes
Media Types
- Selective media, such as those containing bile salts or dyes like basic fuchsin and crystal violet, favor the growth of specific microorganisms.
- Differential media distinguish between different types of microorganisms.
Blood Agar
- Blood agar is used to detect the hemolytic activity of bacteria.
- It distinguishes between hemolytic and nonhemolytic bacteria, with hemolytic bacteria forming clear zones around their colonies.
- The function of blood agar is to detect the hemolytic activity of bacteria by incorporating red blood cells into the medium.
- The differential function of blood agar is to distinguish between hemolytic and nonhemolytic bacteria.
MacConkey Agar
- MacConkey agar is a selective and differential medium that selectively isolates and differentiates lactose-fermenting bacteria.
- Lactose fermenters turn pink or red on MacConkey agar.
- MacConkey agar differentiates between lactose-fermenting and non-lactose-fermenting bacteria.
Mannitol Salt Agar
- Mannitol salt agar is used to isolate staphylococci from clinical and nonclinical samples.
- Staphylococcus aureus ferments mannitol and turns yellow on Mannitol salt agar, while S. epidermidis does not ferment mannitol and remains green.
Eosin Methylene Blue (EMB) Agar
- Eosin methylene blue (EMB) agar is used to detect E. coli and related bacteria.
- The dyes eosin and methylene blue inhibit the growth of Gram-positive bacteria, allowing E. coli and related bacteria to grow.
- The role of Eosin methylene blue (EMB) agar is to detect E. coli and related bacteria by selectively inhibiting Gram-positive bacteria.
Learn about the different types of microbial culture media used in streak plates, including general purpose complex media, selective media, and differential media. Understand how selective media favor the growth of specific microorganisms and the mechanisms involved.
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