Classifications of Culture Media: Selective Medium
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Classifications of Culture Media: Selective Medium

Learn about the functional type of culture media known as selective medium, which allows the growth of specific bacteria while inhibiting others. Explore examples such as Thayer-Martin Agar and its use in isolating Neisseria gonorrhoeae and Neisseria meningitidis.

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Questions and Answers

Which classification of culture media is based on the presence or absence of yeast, plant, or animal tissue?

Synthetic Media

Which type of solid media allows the growth of bacteria as colonies by streaking on the medium?

Non-Liquefiable solid media

Which type of culture media is specifically used for the profuse growth of microorganisms and fermentation studies?

Enrichment media

Which classification of culture media contains ingredients that are not represented by an exact chemical formula?

<p>Non-Synthetic Media</p> Signup and view all the answers

Which type of culture media does not solidify at temperatures above the freezing point and can lead to the formation of a 'surface pellicle' by certain bacteria?

<p>Liquid media</p> Signup and view all the answers

Which type of culture media is entirely free of animal-derived components and useful for studying bacterial physiology and metabolic nature?

<p>Synthetic Media</p> Signup and view all the answers

What is the purpose of semi-solid media prepared with lower agar concentrations?

<p>To determine bacterial motility</p> Signup and view all the answers

Which classification of culture media focuses on promoting the growth of a specific group of microorganisms while inhibiting others?

<p>Selective media</p> Signup and view all the answers

Which classification of culture media is utilized to identify a specific organism based on staining procedures?

<p>Differential media</p> Signup and view all the answers

Which component in Thayer-Martin Agar inhibits gram-positive bacteria?

<p>Vancomycin</p> Signup and view all the answers

What type of bacteria is Mannitol Salt Agar used for the isolation of?

<p>Staphylococcus aureus</p> Signup and view all the answers

In which type of culture media can certain aerobic bacteria grow as a thin film called 'surface pellicle'?

<p>Liquid media</p> Signup and view all the answers

What makes Lowenstein-Jensen Medium selective?

<p>Malachite green dye</p> Signup and view all the answers

Which agar promotes the growth of gram-negative bacteria and inhibits gram-positive bacteria?

<p>MacConkey’s Agar</p> Signup and view all the answers

What is the purpose of Saboraud’s Dextrose Agar?

<p>Promotion of fungal growth</p> Signup and view all the answers

Which agar is recommended for use in qualitative procedures for the isolation of Neisseria gonorrhoeae and Neisseria meningitidis?

<p>Thayer-Martin Agar</p> Signup and view all the answers

Study Notes

Classification of Culture Media by Functional Type

  • Selective Media: allows the growth of one class of bacteria while inhibiting others
    • Examples: Thayer-Martin Agar, Mannitol Salt Agar, MacConkey's Agar, Lowenstein-Jensen Medium, Saboraud's Dextrose Agar
  • Differential Media: designed to show visible differences among certain groups of microorganisms
    • Examples: MacConkey's Agar (promotes growth of gram-negative bacteria and inhibits gram-positive bacteria)
  • Culture Media: a mixture of substances that promotes and supports the growth and differentiation of microorganisms

Purpose of Culture Media

  • To obtain pure cultures
  • To grow and count microbial cells
  • To cultivate and select microorganisms
  • To identify specific organisms based on staining procedures

Classification of Culture Media by Physical State

  • Solid Media: contains a solidifying agent such as agar, allowing bacteria to form discrete colonies
    • TWO FORMS: Liquefiable solid media (reversible) and Non-Liquefiable solid media (non-reversible)
  • Liquid Media: water-based solutions that do not solidify at temperatures above the freezing point
    • Also called broths, milk, or infusions
    • Used for profuse growth of microorganisms and fermentation studies
  • Semi-Solid Media: prepared with lower agar concentrations of 0.5%
    • Used to cultivate microaerophilic bacteria or determine bacterial motility

Classification of Culture Media by Chemical Composition

  • Synthetic Media: defined media with no yeast, plant, or animal tissue present, and all chemicals are known
    • Made from pure ingredients with exact composition known
    • Useful for studying physiology, metabolic nature, and nutritional requirements of bacteria
  • Non-Synthetic Media: complex media containing at least one ingredient that is not chemically defined
    • Contain extracts of animals, plants, or yeasts
    • Support the growth of more fastidious organisms

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