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51 Cards in this Set
- Front
- Back
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How is the total magnification calculated?
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It is calculated by multiplying the magnification of the objective lens times the ocular lens.
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What is resolving power?
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The ability to distinguish fine detail by producing separate images of small parts of a specimen that are only a short distance apart.
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Define aseptic technique.
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Procedures used to prevent contamination of cultures and to protect individuals and the environment from microbial exposure.
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The step by step process to preparing a wet mount, focusing the prepared wet mount under a microscope with each objective from low power to oil immersion.
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Place a drop of water on the center of a glass slide. Place the culture in the drop of water. Place the edge of the cover slip on the drop of water on the slide so that the fluid completely wets the edge. Then slowly lower it into place over the culture.
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List 3 reasons that stained preparations of fixed cells are useful.
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1. more detailed examination of cells 2. the observation of certain cellular components 3. the preliminary differentiation of microorganisms.
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Define Brownian movement.
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A vibrating movement resulting from a bombardment of surrounding materials.
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List 2 reasons that direct examination of live organisms is useful.
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Direct examination of live organisms is useful to determine size and shape relationships, motility, and reactions to various chemicals.
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Define motility.
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Motility is the property of a cell to move a definite distance by its own power.
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Define bacterial colony.
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A bacterial colony is a visible accumulation of a bacterium on a solid culture medium.
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List 4 properties of bacterial colonies visible on a nutrient agar plate or related plate medium.
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The four properties of bacterial colonies are pigmentation, shape, elevation, and the patterns of growth.
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List the 3 forms of growth seen in broth media.
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The three forms of growth are clouding of the medium (turbidity), accumulation of cells at the tube bottom (sediment), and the formation of a thin surface film (pellicle).
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Explain the pour plate method for isolating pure cultures. What are 2 of its disadvantages?
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The pour plate method is cooling a melted agar-containing medium and inoculating the medium with a specimen just prior to pouring it into a sterile Petri plate. Two disadvantages to this method are colonies of several species may present a similar appearance in the agar environment and certain species of bacteria may not grow in this environment.
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In what position are plates incubated and why?
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Petri plates are incubated in an inverted position to prevent water from forming on media surfaces and causing bacterial colonies to run together.
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List 3 categories of organisms based on their oxygen requirements. Describe where each of these categories would be found in a tube of thioglycollate broth.
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Aerobes (grow with oxygen): Upper pink zone
Anaerobes (grow in the absence of oxygen): Lower yellow zone Facultative Anaerobes (grow in the presence or absence of oxygen): Throughout the yellow zone, some grouping in the upper zone |
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Define the terms ecology and ecosystem.
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is the study of the interrelationships between organisms and their respective environments. The ecosystem Ecology is the total community of living organisms together with their chemical and physical environments.
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List the reagents of the Gram stain in order and explain their functions
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Crystal Violet: primary stain, gram + purple, gram - purple
Gram’s Iodine: mordant, gram + purple, gram – purple Acetone-alcohol: decolorizer, gram + purple, gram – no color Safranin: counterstain, gram + purple, gram – red |
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Explain the differences in the cell walls of Gram positive and Gram negative cells. List 2 factors that could affect the outcome of the staining process.
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Gram positive cells have a thick peptidoglycan in their cell walls and the gram negative cells have a very thin layer of peptidoglycan which is why their membranes dissolve during decolonization. The factors that affect the Gram reaction are cell age, autolysin levels, and growth conditions.
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What is an endospore? Name 2 bacterial genera that produce endospores.
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An endospore is a thick-walled, generally highly heat-resistant, resting or dormant form developed within the cell by certain microorganisms during specific stages of their life cycle. Two bacterial genera would include Bacillus and Clostridium.
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What is the primary stain in the spore-stain procedure and why must it be steamed?
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The primary stain is malachite green and it must be steamed to force the penetration of the dye through the relatively impermeable spore coat.
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Define “selective medium” and give an example of one selective media as well as what organism(s) it is selective for.
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Selective medium is defined as one that permits the growth of certain organisms while preventing or retarding the growth of others. Bacto-Brilliant Green gar is a highly selective media used for the isolation of Salmonella species, the causative agent of typhoid fever from stools of other specimens suspected of containing those organisms.
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Define “differential media” and give an example of one.
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Differential media is defined as not preventing the growth of organisms, which would cause certain colonies to develop differently. And an example would be MacConkey agar.
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List 3 possible reactions on blood agar and explain what each of these indicates.
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Alpha hemolysis is indicated by green zones around the colonies. Beta hemolysis is indicated by clear zones around the colonies. Gamma hemolysis is indicated by no zones around the colonies.
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Distinguish between the reactions of lactose fermenters and lactose non-fermenters on Brilliant Green Agar, Eosin-methylene Blue, Hektoen enteric agar, and MacConkey agar.
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Brilliant Green Agar: The lactose fermenter has yellow green colonies surrounded by yellow-green zones. The lactose nonfermenter has pink to white colonies surrounded by brilliant red zones.
Eosin-methylene Blue: The lactose fermenter has park purple colonies with dark centers and transparent colorless borders. The lactose nonfermenter has colorless colonies. Hektoen: The lactose fermenter has salmon-pink colonies. The lactose nonfermenter has mostly green colonies. MacConkey: The lactose fermenter has pink-red colonies surrounded by pink zones. The lactose nonfermenter has colorless and translucent colonies. |
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Describe 2 other types of reactions that can be observed on HEK agar
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HEK can also have Salicin fermenters and Salicin nonfermenters. Salicin fermenter is when there are pink zones around the colonies. And Salicin nonfermenters experience no change.
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What is the indicator used in Durham fermentation?
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The indicator is phenol red.
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Describe the 3 types of reactions in Durham fermentation tube.
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The reactions are yellow which is acidic, red which is alkaline, and finally a gas producing carbohydrate.
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Give two examples of intracellular enzymes that are used by cells for further metabolic degradation of carbohydrates.
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Two examples of these enzymes are maltose and lactase.
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In 1880’s Robert Koch originally used gelatin as a solidifying agent for media. What was the problem with gelatin? How has this factor become helpful?
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Gelatin turned to a liquid at high temperatures and because of its protein nature it could be hydrolyzed by extracellular enzymes produced by several microbial species, which would also turn it into a liquid, thus destroying its value as a solidifying agent. It helped Koch find a more suitable solidifying agent, agar.
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What reagents are used for Oxidase test? Catalase?
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Oxidase testing uses Tetramethyl-para-phenylenediamine, which gives its electrons to the oxidized form of cytochrome c. Catalase testing uses hydrogen peroxide.
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Explain what effect UV light has on DNA. Name and describe 2 methods utilized by some bacteria to repair UV-damaged DNA.
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a. Ultraviolet light is absorbed by bacterial cells, mainly by purine and pyrimidine bases in DNA. The production of thymine dimers is by binding two adjacent thymine bases, which has a major outcome of exposure to UV radiation. The formation of those dimers can result from damage or death to a cell because it can’t properly transcribe or replicate. DNApolymerase and DNAligase are enzymes that repair UV radiation. The dark repair requires enzymatic removal of the distorted thymine dimers. This step give DNA polymerase a chance to synthesize new DNA complementary to the undamaged DNA strand.
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Define the term “mutation” and give 2 examples of mutations in bacteria caused by damage to DNA.
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Mutation is a permanent genetic change. Mutations occur as the result of damaged nucleic acids caused by ultraviolet light. Mutations can include a significant reduction in viable cells, pie-shaped sectors, and the formation of colonies with different pigment.
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What types of cells are most susceptible to UV damage? Why does UV light have a limited application for sterilization purposes?
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Actively multiplying microorganisms are the types of cells that are most susceptible to UV damage. UV light has a limited application because it has a very poor penetration capacity.
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What is an antibiotic? What was the first antibiotic and how was it discovered? What organism produces it?
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An antibiotic is a chemical compound produced by microorganisms and/or synthesized commercially that can inhibit the growth of or kill other microbes. The first antibiotic, penicillin, was discovered by Flemming accidently leaving a petri dish open containing Staphylococcus aureus. A few days later, fungus had contaminated plate, and he found that S. aureus grew everywhere but the area immediately surrounding the fungus. Penicillium notatum is the organism that produces penicillin.
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Explain how filters sterilize.
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Filters sterilize by using the surface of nutrient medium after having been used in the filtering of a fluid containing microorganisms, following the microorganisms colonies will develop after a suitable incubation period. It is important to remember microorganisms can be eliminated but viruses can not.
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Distinguish between bactericidal and bacteriostatic.
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Bactericidal is where microorganisms are able to kill other microorganisms. Bacteriostatic is when the microorganism inhibits growth.
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Describe the appearance of a TSIA tube inoculated with a glucose fermenter. Describe the appearance of a TSIA tube inoculated with a lactose fermenter. For both results, explain why the tubes appear that way.
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The TSIA in an inoculated glucose fermenter appears red (alkaline) in slant formation and yellow (acid) in butt formation. The TSIA in an inoculated lactose fermenter appears yellow in both the slant and butt formations. If the agar reacted with a red appearance it was an alkaline reaction and yellow proved that it was an acidic reaction.
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List the 3 characteristics that can be tested for using SIM media.
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SIM media can be tested for hydrogen sulfide production, indole production, and motility.
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Describe a positive result for glucose and/or lactose fermentation in carbohydrate metabolism media. What indicator is used in this test and what color is it at an acidic pH? What color at a basic pH?
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A positive result for glucose would show red and for lactose would be yellow. The indicator used in carbohydrate metabolism is called phenol red, which concludes yellow acidic and red as alkaline.
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What is the function of the enzyme urease? Describe a positive reaction for a urease test.
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The function of the enzyme urease is to be split into ammonia and carbon dioxide. The carbon dioxide is incorporated into carbohydrate and nitrogen metabolism through a variety of important reactions. A positive reaction for a urease test is indicated by a red color of the medium.
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What does the appearance of a red color after the addition of sulfanilic acid and dimethyl-α-naphthylamine indicate? If no color appears, what 2 possible conclusions could be drawn regarding the test?
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The red color indicates a positive test. If no color appears they test whether nitrate was not reduced to nitrite or whether nitrate was converted to gaseous nitrogen by means of denitrification.
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What amino acid is broken down to produce indole in the IMViC test
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The amino acid tryptophan.
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What reagents are used in the Voges-Proskauer test following incubation? What compound are they testing for?
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The reagents used in the VP test are Naphthol and KOH plus creatine. They are testing for the compound acetoin.
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What is the role of citrase? Describe a positive test result for this enzyme in both Simmons and Koser’s citrate media.
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The role of citrase is to determine the presence of enzymes that enable citrate to enter the cell and then be used as a sole source of carbon for its metabolism and growth. The positive test result for Simmons is growth where the agar turns blue. Koser citrate also shows growth and its medium usually becomes cloudy.
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Define minimal inhibitory concentration. What are 2 factors that could affect the size of growth inhibition zones?
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MIC is the concentration of a drug that will inhibit the growth of another microorganism. Factors that could affect the size of growth inhibition zones include incubation conditions and the concentration of the antibiotics used.
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What are mycolic acids? Name 2 bacterial genera that possess these.
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Mycolic acids are fatty acid chains found in the cell wall of the bacteria. Mycobacterium and Nocardia are two bacterial genera that possess mycolic acids.
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List the reagents of the acid-fast stain in order and give the possible results after each step.
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Carbol Fuchsin is a primary stain that results in red in acid-fast cells and red in non-acid-fast cells. Acid-alcohol is a decolorizer that results in red in acid-fast cells and colorless in non-acid-fast cells. Methylene Blue is a counterstain stain and results in red in the acid-fast cells and blue in the non-acid-fast cells.
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What types of microorganisms can be removed by filtration? What types cannot?
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Microorganisms such as bacteria and yeasts can be removed from fluids, but viruses cannot be eliminated by filtration.
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Explain Universal Precautions.
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Universal Precautions, also known as body substance isolation, was developed by the Centers for Disease Control and Prevention, creating safety procedures that make the health care workplace safer for both health care workers and their patients.
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Define nosocomial infection
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A nosocomial infection is acquired in the hospital from either patient to patient, patient to health care worker, health care workers to other workers, health care worker to patient, or patient to visitor.
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Name 3 of the proper handling requirements for the collection of microbiological specimens for analysis.
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Proper handling requirements are aseptic collection techniques, suitable means of preservation, and suitable means of transporting specimens to the laboratory.
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What two lactose fermenting bacteria are used to make yogurt?
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The two lactose fermenting bacteria are Lactobacillus bulgaricus and Streptococcus thermophilus.
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