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Quizzes > Quizzes for Business > Healthcare

Microbiology Laboratory Techniques Quiz Challenge

Sharpen Your Microbiology Laboratory Technique Skills Today

Difficulty: Moderate
Questions: 20
Learning OutcomesStudy Material
Colorful paper art depicting elements related to Microbiology Laboratory Techniques Quiz

Are you ready to delve into essential lab procedures? This Microbiology Laboratory Techniques Quiz offers a practical way to test your understanding of Gram staining, aseptic transfers, and equipment calibration. Designed for students and lab professionals, it sharpens diagnostic skills and builds confidence in the microbial lab. The quiz integrates insights from other assessments like Microbiology Knowledge Assessment Quiz and Laboratory Safety Knowledge Test. You can freely adapt questions in the editor and explore more quizzes tailored to your learning goals.

Which piece of equipment uses pressurized steam at high temperature to sterilize laboratory materials?
Autoclave
Laminar flow hood
Incubator
Bunsen burner
An autoclave uses pressurized steam at 121°C and 15 psi to sterilize laboratory glassware, media, and instruments. The other options either provide heat without pressure or are used for different purposes.
Which tool is best suited for transferring a small drop of liquid culture to an agar plate?
Pipette filler
pH meter
Spectrophotometer cuvette
Inoculating loop
An inoculating loop is designed to pick up and transfer small volumes of liquid culture onto agar surfaces. The other items are used for measurement or containment rather than direct inoculation.
What is the first step in proper aseptic technique before handling microbial cultures?
Wear gloves
Flame sterilize the inoculating loop
Disinfect the work surface with 70% ethanol
Label culture tubes
Disinfecting the work surface with 70% ethanol removes contaminants and reduces risk of cross-contamination. While wearing gloves and flaming the loop are important, they follow surface disinfection in standard aseptic protocols.
After completing a Gram stain, Gram-positive bacteria appear which color?
Purple
Colorless
Green
Pink
Gram-positive bacteria retain the crystal violet-iodine complex and appear purple under the microscope. Gram-negative bacteria are decolorized and counterstained pink.
Which biosafety level (BSL) is appropriate for working with non-pathogenic E. coli strains?
BSL-1
BSL-4
BSL-2
BSL-3
Non-pathogenic strains of E. coli are handled at BSL-1, which is for agents not known to consistently cause disease. Higher BSLs are reserved for increasingly hazardous pathogens.
During a streak plate procedure, what is the purpose of flaming the loop between quadrants?
To remove moisture from the loop
To kill remaining bacteria on the loop
To sterilize the agar
To cool the loop
Flaming the loop sterilizes it and kills any remaining bacteria, ensuring that each quadrant has a progressively lower cell density. This isolation step is crucial for obtaining discrete colonies.
A micropipette with a volume range of 20-200 µL is most suitable for measuring what volume?
1 mL
5 µL
500 µL
150 µL
A micropipette calibrated for 20-200 µL accurately measures volumes within that range. Volumes outside this range are inaccurate and require different pipettes.
In the Gram staining procedure, what is the role of iodine?
It acts as a mordant to form a complex with crystal violet
It serves as a counterstain
It fixes cells to the slide
It decolorizes Gram-negative cells
Iodine acts as a mordant by forming an insoluble complex with crystal violet in Gram-positive cells, enhancing dye retention. It does not decolorize or counterstain cells.
Why are serial dilutions performed before plating a microbial sample?
To increase microbial growth rate
To obtain countable colony numbers by reducing concentration
To change pH of the medium
To stain the cells evenly
Serial dilutions lower the concentration of microbes so that plated samples yield countable colonies. This allows accurate quantification of the original sample.
If 0.1 mL of a 10^-4 dilution yields 50 colonies on an agar plate, what is the concentration of bacteria in the original sample (CFU/mL)?
5 x 10^7 CFU/mL
5 x 10^5 CFU/mL
5 x 10^6 CFU/mL
5 x 10^4 CFU/mL
50 colonies from 0.1 mL equals 500 CFU/mL at the 10^-4 dilution. Multiplying by 10^4 gives 5 Ã - 10^6 CFU/mL in the original sample.
How often should a laboratory pH meter be calibrated to ensure accurate measurements?
Once a year
Only when pH readings seem incorrect
After every 100 measurements
Daily or before each use
Calibrating a pH meter daily or before each use ensures reliable readings, as electrode response can drift over time. Less frequent calibration risks inaccurate data.
Which biosafety level is required for work with Salmonella enterica, a known pathogenic bacterium?
BSL-2
BSL-4
BSL-1
BSL-3
Salmonella enterica is pathogenic and typically handled at BSL-2, which includes practices to protect personnel and environment. BSL-1 is for non-pathogens, while higher BSLs are for more hazardous agents.
What temperature and pressure settings are standard for sterilization in an autoclave?
121°C at 15 psi for 5 seconds
100°C at 10 psi for 5 minutes
135°C at 5 psi for 30 minutes
121°C at 15 psi for 15 minutes
Standard autoclave sterilization uses 121°C at 15 psi for at least 15 minutes to ensure complete sterilization. Deviations in time, temperature, or pressure compromise effectiveness.
Which feature distinguishes a phase-contrast microscope from a standard brightfield microscope?
It enhances contrast of transparent specimens without staining
It magnifies images using electron beams
It requires solid substrates for imaging
It uses fluorescence to detect antibodies
Phase-contrast microscopy converts phase shifts in light passing through transparent specimens into differences in brightness, allowing visualization without staining. Brightfield requires stains for contrast.
What is the likely result of over-decolorizing with alcohol during a Gram stain?
Gram-positive cells may appear pink
All cells will appear green
Gram-negative cells remain purple
Cells will detach from the slide
Over-decolorization can remove crystal violet-iodine complexes from Gram-positive cells, causing them to take up the pink counterstain and appear Gram-negative. Gram-negative cells are less affected.
You perform serial dilutions of a bacterial culture by transferring 1 mL into 9 mL diluent repeatedly. What is the dilution factor after four transfers?
4 x 10^-1
10^-1
10^-4
4 x 10^-4
Each 1 mL into 9 mL step is a 10^-1 dilution. After four successive dilutions, the total dilution factor is (10^-1)^4 = 10^-4.
During a Gram stain troubleshooting, a student finds both Gram-positive and Gram-negative bacteria stained purple. What step likely caused this error?
Under-decolorization with alcohol
Using old safranin
Skipping the iodine step
Overheating the smear
If the decolorization step is too brief, Gram-negative cells will retain crystal violet and appear purple alongside Gram-positive cells. Proper timing of alcohol application is critical.
When calibrating a spectrophotometer, which of the following steps ensures accuracy across the visible spectrum?
Clean cuvette only after calibration
Use only a single blank at 600 nm
Adjust the lamp voltage for maximum intensity
Perform wavelength calibration with holmium oxide filters
Holmium oxide filters provide known absorbance peaks across the visible range, allowing wavelength accuracy checks. Single-wavelength blanks or lamp adjustments do not verify spectral performance.
Which statement correctly differentiates a Class II biosafety cabinet from a Class I?
Class II allows work with sterile techniques while Class I does not
Class II provides both product and personnel protection, Class I only protects personnel
Class II is not ventilated but Class I is
Class I has HEPA filtered inflow only, Class II has no filters
Class I cabinets protect personnel by directing air inward but do not protect samples. Class II cabinets use HEPA-filtered inflow and downflow to protect both products and personnel.
A plate count of 0.1 mL of a 10^-5 dilution yields 120 colonies, and 0.1 mL of a 10^-6 dilution yields 12 colonies. Which count should you use for the most accurate CFU/mL calculation?
Average of both
100 colonies
12 colonies
120 colonies
The accepted range for countable colonies is typically 30 - 300. The 120-colony count falls within this range and provides the most reliable estimate for CFU/mL calculations.
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Learning Outcomes

  1. Identify common microbiology lab equipment and their uses.
  2. Demonstrate aseptic technique to prevent contamination.
  3. Apply Gram staining procedures to differentiate bacterial types.
  4. Analyse serial dilution and plate count methods for microbial quantification.
  5. Evaluate proper calibration and maintenance of lab instruments.
  6. Master biosafety level protocols for handling microbial cultures.

Cheat Sheet

  1. Essential Microbiology Lab Equipment - Before jumping into experiments, get to know the core gear like microscopes, autoclaves, and incubators. Each tool has its own quirks - think of the microscope as your microbial binoculars and the autoclave as your bacterial zapping oven! Proper handling ensures accurate results and keeps everyone safe. Microbiology Laboratory Equipment
  2. Master Aseptic Techniques - Prevent unwanted contamination by mastering sterilization tricks: flame your loops, sanitize surfaces, and keep those gloves squeaky clean. Imagine you're the guardian of pure cultures, banishing any microbial party crashers! Consistency here means rock-solid, reliable results. Aseptic Techniques in the Microbiology Laboratory
  3. Gram Staining Essentials - Dive into the classic purple-versus-pink showdown! Gram staining separates bacteria based on cell wall secrets, guiding diagnosis and treatment strategies. Nail each step - crystal violet, iodine, decolorizer, safranin - and watch those microbes reveal their true colors under the scope. Gram Staining Protocols
  4. Serial Dilution & Plate Count Techniques - Turn massive microbial crowds into countable squads by diluting samples systematically. Plate them out, incubate, then count the colony-forming units (CFUs) like a microbial census taker. This method is your ticket to quantitative microbiology mastery. Serial Dilution and Plate Count Techniques
  5. Instrument Calibration & Maintenance - Keep your pipettes and spectrophotometers in top shape by regular calibration checks and routine clean-ups. Think of it as maintaining your car - precision tools need precise care to avoid experimental breakdowns and costly headaches. Calibration and Maintenance of Laboratory Instruments
  6. Biosafety Levels Overview - Navigate biosafety levels 1 - 4 like a lab explorer charting uncharted territories. Each tier dictates containment gear, protocols, and facility designs to handle microbes safely. Knowing the rules keeps both you and your samples out of harm's way. Biosafety Levels and Laboratory Practices
  7. Streak Plate Method for Pure Cultures - Isolate individual bacterial colonies by gently streaking samples across an agar plate in strategic zones. It's like spreading butter on toast - thin layers separate cells for easy picking. Pure colonies let you study single species without unwanted neighbors. Streak Plate Method for Isolation
  8. Selecting the Right Media - Different bacteria have different dietary needs! Use selective media to give certain microbes a VIP pass and differential media to color-code them based on metabolic traits. It's a microbial buffet with secret sauces revealing who's who. Selective and Differential Media in Microbiology
  9. Optimizing Incubator Conditions - Fine-tune temperature, humidity, and sometimes gas composition to create the ultimate microbe spa. Proper incubation settings ensure your tiny guests thrive and deliver consistent experimental outcomes. No one likes a moody microbe! Incubation Conditions in Microbiology
  10. Microbial Identification Methods - From old-school biochemical tests to cutting-edge molecular tools, identify microbes with confidence. Think of it as detective work: each test uncovers clues about bacterial identity and behavior, critical for research and diagnostics. Microbial Identification Methods
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