Lab Flashcards
What should you do before and after using work areas in the lab?
Disinfect work areas before and after use.
What are the key safety practices in the lab?
Treat all microorganisms as potential pathogens, sterilize equipment and materials, wash hands, do not eat or drink in the lab, label everything clearly, and autoclave or disinfect all waste material.
What information should be included when labeling samples?
Date, name of microorganism, number table, afternoon class, and initials.
What is the purpose of a graduated cylinder?
A graduated cylinder is used to measure the volume of a liquid.
What is the difference between a scale and a graduated cylinder?
A scale is used for accuracy, while a graduated cylinder measures liquid volume.
What are the grading divisions for 100mL and 10mL graduated cylinders?
100mL cylinders have 1mL grading divisions, while 10mL cylinders have 0.1mL grading divisions.
What is the recommended temperature for a fridge?
A fridge should be set to maintain a temperature of 40 °F or below.
What is the temperature range for a freezer?
A freezer temperature ranges from -20 to -40 °C.
What are positive and negative controls in experiments?
Positive controls verify that an organism grows successfully, while negative controls verify the testing environment and handling.
What is the magnification capability of compound microscopes?
Compound microscopes can magnify an object by 400 times or more, up to 1,000 times.
What is the typical magnification for dissecting microscopes?
Dissecting microscopes usually magnify an object by 40 times or less.
What is immersion oil used for in microscopy?
Immersion oil is used to increase the resolving power of a microscope by immersing both the objective lens and the specimen in oil.
What is the purpose of a 4-way streak?
The purpose of a 4-way streak is to obtain single, isolated colonies of a microorganism.
What is the protocol for performing a 4-way streak?
A sterile inoculating loop is dipped into a mixed culture and streaked over the surface of the nutrient medium to separate bacteria.
How can you reduce contamination while working aseptically?
Open the lid of the agar plate just enough to streak it and minimize exposure to the environment.
What is the function of an autoclave?
The autoclave is used to sterilize materials.
What are the main types of bacterial cell morphology?
Cocci, bacilli, spirochetes, and spirillum.
What are the arrangements of bacterial cells?
Chains, tetrads, and clusters.
What terminology should be used to describe bacterial colony morphology?
Use the terms provided in the lab manual.
What are the main types of bacterial cell morphology?
Cocci, bacilli, spirochetes, and spirillum.
What are the common arrangements of bacterial cells?
Chains, tetrads, and clusters.
What terminology is used to describe bacterial colony morphology?
Terms from the lab manual.
Which genera of bacteria should be recognized for their cell morphology?
Staphylococcus, Streptococcus, Bacillus, Escherichia, Enterobacter, Pseudomonas, Salmonella, Shigella.
What are the steps involved in the Gram stain?
Understand the steps and be able to troubleshoot the Gram stain.
What is the advantage of endospores in bacteria?
Endospores protect bacteria from adverse environmental conditions.
Why can’t endospores be stained by ordinary methods?
Dyes do not penetrate the wall of the endospore.
What happens to cells after staining with carbolfuchsin?
Cells appear reddish-purple.
What is the purpose of steam heat in staining?
It enhances the entry of carbolfuchsin into cells.
What does decolorization with acid alcohol do?
Removes stain from acid-fast negative cells.
What is used to counterstain acid-fast negative cells?
Methylene blue.
What color do acid-fast cells stain?
Reddish-purple.
What color do acid-fast negative cells stain?
Blue or the color of the counterstain.
What types of stains should you be able to identify?
Gram stain, capsule stain, spore stain, and flagellar stains.
What is the importance of media in bacterial culture?
Media is used to grow and differentiate bacteria.
What distinguishes defined/synthetic media from complex media?
Defined media has known ingredients, while complex media has unknown components.
What are differential and selective media?
Types of agar that can exclude certain bacteria and test for metabolic capabilities.
What are examples of specialized media?
MacConkey’s (MAC), Blood agar (BAP), and Mannitol Salt (MSA).
How can you read results from differential media?
By observing characteristic changes or growth patterns.
What is colony morphology?
Characteristics of a colony such as shape, size, and pigmentation.
Why are petri plates inverted during incubation?
To prevent condensation from contaminating the samples.
What are the exceptions for knowing specific results of organisms?
S. aureus on mannitol salt and E. coli on EMB.
What does the Oxidation Fermentation (OF) test assess?
It assesses the metabolic capabilities of bacteria.
What is the purpose of the Oxidation-Fermentation (O-F) Test?
The O-F Test is designed to differentiate bacteria based on fermentative or oxidative metabolism of carbohydrates.
Why is one tube covered with oil in the O-F Test?
One tube is sealed with sterile mineral oil to promote anaerobic growth and fermentation, while the other tube is left unsealed for aerobic growth and oxidation.
What does it mean when both oil covered and uncovered tubes are yellow?
It indicates that organisms are able to ferment the carbohydrate or ferment and oxidize the carbohydrate.
What does it mean when the oil covered tube is green, but the uncovered tube is yellow at the very top?
It indicates that the organism is able to oxidize only.
What does it mean when both tubes are slightly yellow at the top?
It indicates oxidation and slow fermentation or slow fermentation only.
What does it mean when the sealed tube is green or blue?
It indicates no sugar metabolism; the organism is nonsaccharolytic.
What is the purpose of Phenol Red Broth?
Phenol Red Broth is a general-purpose fermentation medium that detects acid formation.
What is the function of the Durham tube in the Phenol Red test?
An inverted Durham tube is added to indicate gas production.
How does the Methyl Red test differ from the Phenol Red test?
The Methyl Red test detects mixed acid fermentation, while Phenol Red tests for general fermentation.
What is the purpose of the Voges-Proskauer (VP) test?
The VP test is designed for organisms that ferment glucose and convert acid products to acetoin and 2,3-butanediol.
What end product does the VP test look for?
The VP test looks for acetoin, which oxidizes to diacetyl and produces a red color when reacted with VP reagents.
What indicates a positive result in the VP test?
A positive VP result is indicated by a red color.
What does no color change or a copper color indicate in the VP test?
No color change or development of copper color indicates a negative result.
What does a positive result for catalase look like?
Catalase converts hydrogen peroxide into water and gaseous oxygen. When hydrogen peroxide is added to a catalase-positive culture, oxygen gas bubbles form immediately. If no bubbles appear, the organism is catalase-negative.
What does a positive result for catalase tell you about the organism?
This test is used to identify organisms that produce the enzyme catalase. It is used most commonly to differentiate members of the catalase-positive Micrococcaceae from the catalase-negative Streptococcaceae.
What solution is used for the catalase test?
Hydrogen Peroxide
What is the oxidase test detecting?
This test is used to identify bacteria containing the respiratory enzyme cytochrome c oxidase. It is useful in differentiating the oxidase-negative Enterobacteriaceae from the oxidase-positive Pseudomonadaceae.
What does it mean if an organism is negative in the oxidase test?
Lack of color change within the allotted time means that cytochrome c oxidase is not present and signifies a negative result.
What is in the strip that allows you to determine if an organism is positive in the oxidase test?
In the oxidase test, the reducing reagent is added directly to bacterial growth on solid media, or a bacterial colony is transferred to paper saturated with the reagent. A dramatic color change occurs within seconds if the reducing agent becomes oxidized.
What does the nitrate reduction test look for?
Virtually all members of Enterobacteriaceae perform a one-step reduction of nitrate to nitrite. The nitrate test differentiates them from Gram-negative rods that either do not reduce nitrate or reduce it beyond nitrite.
What does a positive test look like in the nitrate reduction test?
If present, nitrite will form nitrous acid (HNO2) in the aqueous medium. Nitrous acid reacts with the added reagents to produce a red, water-soluble compound, indicating that the organism reduced nitrate to nitrite.
What does a negative result look like in the nitrate reduction test?
If no color change takes place with the addition of reagents, the nitrate either was not reduced or was reduced to one of the other nitrogenous compounds. Another test must be performed to differentiate these occurrences.
If an organism is positive for citrate utilization, what does this signify?
Growth on a Simmons Citrate slant indicates that citrate is being utilized. Occasionally, a citrate-positive organism will grow without producing a change in color due to incomplete incubation.
What does the cytochrome c oxidase test indicate?
A dramatic color change occurs within seconds if the reducing agent becomes oxidized, indicating that cytochrome c oxidase is present.
What does the nitrate reduction test look for?
It differentiates members of Enterobacteriaceae that perform a one-step reduction of nitrate to nitrite from Gram-negative rods that do not reduce nitrate or reduce it beyond nitrite.
What does a positive nitrate reduction test look like?
Formation of a red color after the addition of reagents indicates that the organism reduced nitrate to nitrite.
What does a negative result in the nitrate reduction test look like?
If no color change occurs with the addition of reagents, the nitrate was either not reduced or reduced to other nitrogenous compounds.
What does a positive citrate utilization test signify?
Growth on a Simmons Citrate slant without a color change indicates that citrate is being utilized.
Why do you cover the decarboxylation tubes with oil?
An overlay of mineral oil seals the medium from external oxygen and promotes fermentation.
What does a positive result look like in the decarboxylation test?
The medium turns purple due to the accumulation of alkaline end products from decarboxylation of the amino acid.
What should you remember when naming a genus?
Provide the genus name only, e.g., Escherichia = genus and Escherichia coli = species. Both genus and species are italicized; genus is capitalized and species is lower case.
What should you state when describing a Gram-stained organism?
Indicate whether it is Gram positive or Gram negative along with a description, e.g., cocci in clusters or bacilli.
What is the primary purpose of a lab exam?
To assess a student’s practical skills and understanding of laboratory techniques.
True or False: Lab exams typically include both theoretical and practical components.
True
Fill in the blank: In a lab exam, students are often required to follow ________ to ensure safety.
safety protocols
What is a common laboratory technique used to separate mixtures?
Chromatography
Multiple Choice: Which of the following is NOT a common lab safety equipment? A) Goggles B) Gloves C) Calculator D) Lab coat
C) Calculator
What does the term ‘pipetting’ refer to in laboratory practice?
The process of measuring and transferring a liquid using a pipette.
True or False: It is acceptable to eat or drink in the laboratory.
False
What should you do if you spill a chemical in the lab?
Notify the instructor and follow the spill protocol.
Fill in the blank: The ________ measures the temperature of a liquid in the lab.
thermometer
Multiple Choice: Which of the following is a common indicator for pH testing? A) Litmus paper B) Thermometer C) Microscope D) Beaker
A) Litmus paper
What is the purpose of a control group in an experiment?
To provide a baseline for comparison against the experimental group.
True or False: All lab results must be recorded in a lab notebook.
True
What is the formula for calculating concentration?
Concentration = Amount of solute / Volume of solution
Fill in the blank: A ________ is used to hold liquids while heating them.
beaker
Multiple Choice: Which laboratory technique is used to measure the volume of a liquid accurately? A) Beaker B) Graduated cylinder C) Test tube D) Flask
B) Graduated cylinder
What is the significance of repeating experiments?
To verify results and ensure reliability.
True or False: It is important to label all samples and reagents clearly.
True
What is the function of a centrifuge in the lab?
To separate components of a mixture based on density.
Fill in the blank: ________ is the process of observing and recording data in an experiment.
Data collection
Multiple Choice: Which of the following is a qualitative observation? A) The solution is blue B) The solution has a volume of 100 mL C) The temperature is 25°C D) The mass is 50 grams
A) The solution is blue
What is the role of a hypothesis in scientific experiments?
To provide a testable prediction based on observations.
True or False: All laboratory waste should be disposed of in regular trash bins.
False
What instrument is used to measure mass?
Balance
Fill in the blank: The ________ is the part of the experiment that is changed or manipulated.
independent variable
Multiple Choice: Which of the following is an example of a quantitative measurement? A) The liquid is clear B) The solution has a pH of 7 C) The temperature is warm D) The sample is heavy
B) The solution has a pH of 7
What is the purpose of using a microscope in the lab?
To magnify small objects or organisms for observation.
True or False: Lab exams can include questions on theoretical knowledge as well as practical skills.
True
