Microbiology Lab Techniques Study Guide

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary reason for using immersion oil with the oil immersion lens?

To increase the numerical aperture and improve resolution. (correct)

To improve contrast by reducing scattering of light.

To increase the magnification of the objective lens.

To prevent damage to the objective lens by reducing friction.

Which of the following actions is NOT considered a proper aseptic technique?

Cooling the inoculating loop before introducing it into the culture.

Holding a test tube at a 45° angle when transferring culture.

Leaving the lid of a petri dish open while transferring culture. (correct)

Flaming the inoculating loop before and after use.

Which of the following characteristics is NOT typically observed in bacterial growth in a broth culture?

Turbidity (cloudiness)

Uniform distribution of bacteria throughout the broth (correct)

Surface film formation

Pellet formation at the bottom

When performing a 4-quadrant streak plate, what is the primary goal?

To isolate individual bacterial colonies from a mixed culture. (A) Signup and view all the answers

Which of the following is NOT a potential source of contamination to microbial cultures?

Using a sterile inoculating loop for transfer. (A) Signup and view all the answers

What is the term that describes the ability to distinguish between two closely spaced objects as separate entities under a microscope?

Resolution (C) Signup and view all the answers

Which of the following actions is NOT critical for proper handling of a Bunsen burner?

Leaving the burner unattended while it's lit. (B) Signup and view all the answers

What is the primary function of a wet mount in microscopy?

To observe bacteria in their natural state. (A) Signup and view all the answers

What type of staining technique is used to identify the presence of Trichomonas in a wet mount?

No staining is required for a wet mount (B) Signup and view all the answers

Which of the following bacterial shapes is NOT named after its scientific name?

E. coli (C) Signup and view all the answers

What is the main purpose of heat-fixing a bacterial smear before staining?

To preserve the bacterial morphology and prevent them from washing off during staining (B) Signup and view all the answers

Which of the following is NOT a component of a Gram stain?

Methylene blue (A) Signup and view all the answers

What is the primary reason for performing a Gram stain?

To distinguish between Gram-positive and Gram-negative bacteria (C) Signup and view all the answers

Study Notes

Lab Exam 1 Study Outline

Lab Safety and Techniques: Review Lab Safety quiz (pages 1-4). Focus on proper Bunsen burner use, flame recognition, inoculating loop technique, tube capping, handling materials, and inoculation procedures for broths, slants, and plates.

Microscopy - Lab 1

Microscope Parts: Learn the parts of the microscope and their functions.
Microscopy Terms: Understand parfocal, resolution, and the reason oil immersion lenses use oil (same refractive index as glass to avoid light loss due to air).
Magnification: Calculate total magnification.

Aseptic Technique - Labs 2-7

Transfer of Cultures: Understand how to transfer cultures from slants, broths, or plate colonies.
Inoculation: Learn how to inoculate slants, broths, and plates.
Slide Preparation: Practice making wet mounts and heat-fixed smears.
Contamination Control: Know possible sources of contamination (e.g., leaving cultures open, improper angle of holding).

Growth - Labs 2 and 7

Growth Characteristics: Understand bacterial growth characteristics in broth.
Streak Plate Technique: Master the 4-quadrant streak plate method to isolate mixed cultures.
Pure Colonies: Recognize the goal of obtaining pure colonies using the streak plate technique.

Clinical Specimens

Collection and Transport: Understand parameters for collecting/transporting clinical specimens. Refer back to the review quiz on page 2-12.
Specimen Microscopy (Labs 3 & 4): Identify various specimens under a microscope, such as Trichomonas, Ova and Parasites.
Bacterial Shapes Identification Learn to recognize and name bacterial shapes: cocci, bacilli, and spirilla. Use their scientific terms.

Staining - Simple, Lab 4

Simple Stains: Understand how a simple stain, like methylene blue, works by knowing the charge of the stain.

Staining - Gram, Lab 5

Gram Staining Procedure: Learn the Gram staining process, focusing on the roles of crystal violet, iodine, decolorizer, and safranin in differentiating Gram-positive and Gram-negative bacteria.
Mordant role: Identify the role of iodine in the Gram-stain process.
Practical Application: The reason why Gram staining is useful, i.e., identifying bacteria in less than 5 minutes.
Culture Age: Understand why young cultures are important for reliable staining results.

Staining - Endospore, Lab 6

Endospore Staining Procedure: Learn the technique for identifying endospore-forming bacteria.
Heat Role: Use of heat fixing is necessary to drive the malachite green stain into the endospore.
Importance of Bacterial Culture Age: Recognize why older cultures are necessary.
Endospore Recognition: Can differentiate between endospores and vegetative bacterial cells.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Prepare for your microbiology lab exam with this comprehensive study outline covering lab safety, microscopy, and aseptic techniques. Focus on mastering the parts of a microscope, proper inoculation methods, and contamination control to excel in your practical assessments.