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Questions and Answers
What are the chemicals added to help identify bacteria?
What are the chemicals added to help identify bacteria?
Peptone water sugars, Urea broth, Kligler iron agar
What is generation time in bacteria?
What is generation time in bacteria?
The time required for a cell or population to divide
What is the Gram stain used for?
What is the Gram stain used for?
- Determine metabolic activity
- Identify shape of bacteria
- Measure bacterial growth
- Differentiate between Gram-positive and Gram-negative bacteria (correct)
Gram-positive bacteria have a higher lipid content than Gram-negative bacteria.
Gram-positive bacteria have a higher lipid content than Gram-negative bacteria.
Which of the following tests is used to differentiate motile from non-motile bacteria?
Which of the following tests is used to differentiate motile from non-motile bacteria?
What function does coagulase serve?
What function does coagulase serve?
What does the catalase test detect?
What does the catalase test detect?
Oxidase test is used to detect the presence of cytochrome c oxidase in all bacteria.
Oxidase test is used to detect the presence of cytochrome c oxidase in all bacteria.
In sugar fermentation tests, the ability to ferment various sugar samples is tested to determine the organism's __________.
In sugar fermentation tests, the ability to ferment various sugar samples is tested to determine the organism's __________.
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Study Notes
Identification Media
- Chemicals are used to aid in identifying isolated bacteria through color changes or gas production.
- Common identification media include:
- Peptone water sugars
- Urea broth
- Kligler iron agar
Growth of Bacterial Culture
- Generation time refers to the duration needed for bacterial cells to divide.
- Bacterial populations grow rapidly, leading to an increase in metabolic activity without immediate changes in overall cell numbers.
- A balance is established when the number of dead cells exceeds the formation of new cells.
Tests to Differentiate Bacteria
-
Gram Stain:
- Developed by Hans Christian Gram in 1844.
- Distinguishes between Gram-positive (higher peptidoglycan, lower lipid content) and Gram-negative bacteria.
- Reveals:
- Stain positivity or negativity.
- Bacterial shape (cocci, bacilli, spiral).
- Cell arrangement (Staphylococci, Streptococci, Diplococci).
-
Motility Tests:
- Differentiate motile from non-motile bacteria using:
- Hanging drop method.
- Semisolid culture media.
- Differentiate motile from non-motile bacteria using:
-
Biochemical Characteristics:
- Catalase Test: Identifies presence of catalase enzyme.
- Oxidase Test: Detects cytochrome c oxidase enzyme, crucial in electron transport.
- Coagulase Test: Measures ability to clot plasma, aiding in evasion of the host’s immune response.
- Sugar Fermentation Tests: Assesses organisms' ability to ferment various sugars.
Summary of Key Tests
- Gram Stain: Fundamental for identifying bacterial types and arrangement.
- Motility: Essential in determining the movement capability of bacteria.
- Biochemical Tests: Provide insight into metabolic pathways and defense mechanisms of bacteria.
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