Microbiology Lab Techniques Quiz

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Questions and Answers

What is the primary goal of employing aseptic techniques in a microbiology lab?

To enhance the growth rate of microorganisms.

To accelerate the process of serial dilutions.

To introduce mixed cultures into samples.

To prevent contamination of the lab, samples and personnel. (correct)

Which method is primarily used to obtain a pure culture from a mixed culture?

Serial dilution

Pour plate method

Stab culture

Streak plate method (correct)

What is a 'mixed culture' in microbiology?

A culture containing a single type of organism.

A culture where multiple types of organisms are present. (correct)

A culture that is obtained after performing serial dilutions only.

A culture resulting from a streak plate.

In the context of microbiology, what does 'isolation' specifically refer to?

The process of extracting a pure colony from a mixed culture. (C) Signup and view all the answers

Which inoculation method is best for quantifying colony-forming units in a bacterial sample?

Pour plate or Spread plate method (A) Signup and view all the answers

What is the primary purpose of using a coverslip in the wet mount and hanging drop techniques?

To prevent the specimen from drying out and to flatten out the liquid. (A) Signup and view all the answers

Which of these is NOT a material used in the listed activities?

Bunsen burner (C) Signup and view all the answers

What is the purpose of the vaseline in the hanging drop technique?

To seal the coverslip to the slide, creating a moist chamber. (A) Signup and view all the answers

What is the correct order for the Gram staining procedure, based on provided materials?

Crystal Violet, Gram's Iodine, Safranin (A) Signup and view all the answers

Why is it important to use clean slides and coverslips in microscopy?

To prevent contamination and ensure a clear view of the specimen. (A) Signup and view all the answers

What is the primary purpose of Gram staining?

To differentiate bacterial cells based on their cell wall structure. (C) Signup and view all the answers

Which of these is a key difference between Gram-positive and Gram-negative bacteria?

Gram-negative bacteria possess an outer lipid membrane containing lipopolysaccharides, which is not present in Gram-positive bacteria (B) Signup and view all the answers

Which of the following specimens are prepared on two slides for the wet mount procedure described in the protocol?

Thin leaf or decaying fruit (D) Signup and view all the answers

At what magnification should the cut-out letter 'e' be viewed under the microscope?

4x (D) Signup and view all the answers

What is the correct order of reagents in a Gram stain?

Crystal violet, Gram's iodine, 95% Ethanol, Safranin (A) Signup and view all the answers

Which of the following is NOT a liquid added to a slide as part of a preparation?

Yogurt (B) Signup and view all the answers

According to the provided information, what is the morphology of Bacillus subtilis?

Bacillus (D) Signup and view all the answers

What does the term 'morphology' refer to in microbiology?

The shape of a cell (C) Signup and view all the answers

Which of the following is NOT a reagent used in Gram staining?

Methylene blue (A) Signup and view all the answers

What is contained within the cell wall of Gram-positive bacteria, in high %?

Peptidoglycan (D) Signup and view all the answers

What is the correct order of steps in the procedures for the first Microscopy Lab activity?

Letter 'e' mounting, Wet Mount (C) Signup and view all the answers

Study Notes

Microbiology and Parasitology (Laboratory)

BIOL 014 is a course offered by the Polytechnic University of the Philippines, College of Science, Department of Biology.
The course covers laboratory discussions on various topics, including microscopy, slide preparations, different types of microscopes, micrometry, and staining techniques.
Microscopy allows the study of living organisms and species not visible to the naked eye.
- Sir Antonie van Leeuwenhoek invented the first microscope using a single lens, magnifiying 300x.
- Later, double lens microscopes were invented in the late 16th century.
Different types of microscopes exist.
- Bright-field microscopes produce a dark image against a brighter background, having multiple objective lenses.
- Dark-field microscopes produce a bright image against a dark background, useful for viewing unstained living cells.
- Phase-contrast microscopes enhance contrast and allow viewing of internal cellular components and examining growth of living cells.
- Fluorescence microscopes use ultraviolet, violet, or blue light to view samples stained with fluorochromes; showing bright images of objects from fluorescent light.
- Electron microscopes use electrons, having high energy, to examine very fine objects at a very fine scale (transmission and scanning types).
Micrometry is the science of measuring specimen dimensions.
- Stage and ocular micrometers are used, with the stage micrometer being calibrated.
Slide preparations (wet mount, hanging drop, staining) involves specific procedures to observe cell activities (motility, binary fission), natural sizes, and cell shapes
Gram staining is a differential staining procedure to distinguish Gram-positive and Gram-negative bacteria based on cell wall structures.
- Gram-positive bacteria have thick cell walls with peptidoglycan.
- Gram-negative bacteria have thin cell walls with a second lipid membrane called lipopolysaccharides.
Biochemical assays are used to detect, quantify, or study microbial biochemical activities, aiding in identifying microbial species, their metabolic pathways, and roles in different environments.
Oxygen requirements of microorganisms are used to classify them (aerobes, obligate, facultative, microaerophilic, aerotolerant, and anaerobes).
Aseptic techniques are critical for avoiding contamination in microbiological procedures.
Cultural characteristics involving observations of colony size, shape, pigmentation, opacity, and surface features and growth rate of colonies and other aspects of pure and mixed cultures are also observed through the use of various media and other apparatuses.
Several techniques for isolating microorganisms are available such as serial dilution, streak method, pour plate, and spread plate
Antibiotic assays that involve dilution and diffusion assays are used to measure the effectiveness of various antibiotic types on microbial strains as well as the factors like genetic mutations that affect antibiotic resistance.
Standard plate count method is used for estimating the population density of bacteria in a broth based on valid counts (bacteria 25-250, and molds 10-150).
Various types of culture media are examined in relation to their consistency, nutritional ingredients and functional use (liquid, solid and semi-solid, simple, complex, chemically defined media, enriched, selective, differential, and transport media).
Different assays are explained through chemical and or media components used for testing bacterial species (catalase test, urea test, gelatin hydrolysis tests, and lipid hydrolysis tests) including media type and temperatures used
Laboratory activities include procedures to isolate fungi from spoiled fruits and vegetables to examine samples using the appropriate technique (macroscopic and microscopic examination, including use of stain like lactophenol cotton blue).

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Description

Test your understanding of aseptic techniques, pure culture methods, and microscopy in microbiology. This quiz covers essential concepts such as the Gram staining procedure, mixed cultures, and the use of coverslips in various techniques. Challenge yourself to see how well you know microbiological practices and procedures.