Lab Exam 2 Test Answers – Flashcards
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| The process of identifying an “unknown” bacterium is a rational and sequential procedure. What is the 1st step in attempting to identify the “unknown”? |
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| Obtaining a pure culture |
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| What is the 2nd step in identifying an unkown? |
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| Performing a gram stain |
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| List 3 pieces of information that can be determined from a Gram stain |
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| 1. Gram reaction 2. Cell shape 3. cell arrangement |
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| list the 4 genus mentioned in the lab manual that are able to fix nitrogen |
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| Rhizobium, Azobacter, Cyanobacteria, Clostridium |
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| Symbiosis |
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| Living together in the same environment |
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| Symbioants |
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| organisms that live together in a particular environment |
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| name 2 enzymes that are involved in notrogen fixation |
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| Nitrogenase and Transaminase |
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| name two end products of nitrogen fixation |
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| Ammonia and Amino Acids(-> proteins) |
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| List 3 types of symbiotic relationships and describe each one |
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| 1. commensalism: the microbe benefits, the host is neither benefited or harmed 2. mutualism: the host and microbe both benefit each other 3. parasitism: the microbe benefits at the expense of the host |
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| Rhizobium and legume plants are an example of which type of symbiotic relationship? why? |
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| Mutualism; because the Rhizobium cannot fix nitrogen without without a legume and it also obtains energy from carbohydrates synthesized by the plant, and the fixation gives the legume nitrogen that it can use for growth of plant parts |
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| what is the Gram reaction and cell shape of Rhizobium cells? |
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| Gram-negative rods |
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| List 6 characteristcs of Staphylococci |
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| 1. Saprophytes and parasites of skin and mucus membranes 2. Gram-positive cocci arranged in clusters 3. Medium sized, off white or yellow colonies 4. faculative anaerobes 5. tolerant of high NaCl concentration 6. produces catalase |
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| Where are Staph found in the body? |
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| skin and mucus membranes, especially nasopharynx and uppermost part of pharynx that is continuous with nasal passages |
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| Give one example of a pathogenic Staphylococcus |
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| Staph aureus |
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| Give 2 examples of a Staph that is non-pathogenic |
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| Staph epidermis and Staph saprophyticus |
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| what test can be used to differentiate between the pathogenic and non-pathogenic Staph? |
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| the coagulase test |
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| List 4 diseases caused by Staph aureus |
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| 1. wound infections 2. pneumonia 3. toxic shock syndrome 4. food poisening |
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| List 7 characteristics of Streptococci |
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| 1. Saprophytes and parasites 2. Gram-positive coccie arragned in chains or pairs; small white colonies 3. More fastidious 4. faculative anaerobes 5. lactose fermenters 6. not catalse producers 7. no NaCl tolerance |
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| Streptococci are divided into 3 groups according to their type of hemolytic reaction. List and describe these groups |
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| 1. Alpha: hemolysins partially lyse red blood cells and reduce hemoglobin(red pigment) to methemoglobin(green pigment) 2. Beta: hemolysins completely lyse RBCs and decolorize the hemoglobin 3. Gamma: no lysis occurs |
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| 3 characteristics of Hemolysins: |
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| 1. lyse RBCs 2. are produced by pathogenic bacteria 3. play a role in the virulence of the pathogenic organisms via aidning the infecting organism to escape some of the hosts productive mechanisms(such as blood clot formation) |
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| what is the function of the coagulase enzyme? |
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| clots blood plasma without using thrombin |
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| How is the result of the mannitol fermentaion interpreted? |
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| If mannitol is fermented, the agar turns from pink to yellow |
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| what is the correlation between the Mannitol Fermentation test and the Coagulase test? |
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| if one is positive, the other one will be too |
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| Describe the Bile-Esculin test |
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| Group D Strep can hydrolize bile-esculin into eculectin and glucose. Esculectin can be visualized by adding gerric citrate, which forms a black/grey complex |
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| Explain the principle of the NaCl tolerance test |
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| Group D Strep arethe only group of strep resistant to Salt |
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| How is the NaCl tolerance test interpreted? |
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| Positive result= turbidity in NaCl broth and/or deep purple color change to light purple |
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| List 7 characteristics of the enteric organisms |
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| 1. Gram (-) 2. faculative anaerobes 3. oxidase negative 4. catalse (+) 5. non-spore forming 6. ferment glucose 7. rod shaped |
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| What 2 diseases are caused by genus Escherichia? |
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| Typhoid fever and acute gastro enteris |
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| which 3 genuses are frequently found in Urinary Tract infections but not GI tract? |
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| Hafnia, Morgonella, Providencia |
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| Coliform |
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| Gram-negative, non-spore forming, faculatively anaerobic rods that can ferment lactose |
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| Differential media |
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| contains ingredients designed to elicit a specific biochemical of physiological response, allowing different groups to be differeintiated |
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| List 3 examples of differential media and what the differentiate |
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| 1. MacConkey Agar- lactose fementers 2. Bile Esculin Agar- Esculin hydrolysis 3. Mannitol Salt Agar- mannitol fermentation |
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| Selective media |
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| contains components that inhibit growth of unwanted bacteria, thus selecting bacteria that are resistant to the components |
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| some media are both selective and differential, give 2 examples |
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| MacConkey Agar and Mannitol Salt Agar |
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| TSI(Triple Sugar Iron) agar can detect: |
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| 1. glucose, sucrose, lactose fermentation 2. gas production 3. H2S production |
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| A yellow butt in the TSI agar indicates: |
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| glucose fermentation |
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| a yellow TSI slant indicates: |
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| sucrose/ lactose fermentation |
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| IMVIC is a combination of which 4 tests? |
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| Indole, Methyl-Red, Vogues-Proskauer, Inorganic Citrate |
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| The enterotube has 12 chambers and can perform how many tests simultaneously? |
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| 15 |
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| The enterotube can identify the level of... |
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| species |
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| Non-invasive organisms |
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| do not invade the tissues and cause damage, instead they reside on the surface |
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| opportunists |
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| can cause disease of the host defenses are lowered of if the balance between bacteria and normal flora is disrupted |
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| pathogenic organisms |
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| sometimes invade the body and cause disease of they can get past defenses |
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| What is the one weakness of the Kirby-Bauer Disc method? |
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| it does not determine if an organism is bacteriostatic of bacteriocidal |
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| Bacteriostatic organism |
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| inhibits growth but does not kill |
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| Bacteriocidal organism |
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| inhibits growth and induces killing |
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| List the 9 factors that affect the size of inhibition zones |
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| 1. Sensitivity or organism 2. molecular size 3. concentration of agent 4. density of culture 5. rate of diffusion of agent 6. size of inoculum 7. time of incubation 8. temperature of incubation 9. interactions between agent and medium |
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| Name two antibiotics that are small in size |
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| Pecicillin and ampicillin |
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| Name 2 antiobiotics that are large in size |
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| Poolymyxin B and bacitracin |
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| MIC (minimal inhibitory concentration) |
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| lowest concentration that prevents visible growth but not killing |
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| MBC (minimal bacteriocidal concentration) |
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| lowest concentration that prevents visible growth and induces killing |
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| Bacteriolytic |
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| lyses cells and is observed as a decrease in cell number or turbidity |
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| Synergism |
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| the antimicrobial effect of two drugs used simultaneously is greater than tha of the drugs when used seperately |
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| antagonism |
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| combination of two drugs interferes with each other's mechanisms and renders them ineffective |
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| Citrate Utilization -how does the medium change and why-what is the indicator? |
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| Produce NH3(alkaline) --> Simon citrate slant medium changes green to blue due to a rise in pH. Bromothymol blue is the indicator |
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| How does Carbohydrate Fermentation and Gas Production in Durham tubes? What is the indicator? |
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| the tube changes from green to yellow due to a drop in pH. BTB is the indicator |
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| Indole Production Test |
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| indole--> intermediate metabolite in breakdown of tryptophan(amino acid) -presence of enzyme tryptophase -Kovac's reagent--> reacts with indole-->red |
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| Methyl Red Test |
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| tests for mix acids production from glucose fermentation. Turns red at pH below 4.4. Large acid: alcohol ratio. equal C02:H2 ratio. MR-VP medium-->add methyl red--> red is positive result. indicates the fermentation of glucose |
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| Vogue-Proskauer Test (Butanediol Fermentation) |
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| also indicates fermentation of glucose to 2,3 butanediol and ethanol. detects the presence of acetoin. high alcohol:acid ratio. large amount of gas is produced, large C02:H2 ratio. MR-VP medium, add Barritts A and B--> wait for 20 minutes--> pink/red = positive |
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| 3 Categories of Biological and Enzymatical Reactions Used to Identify Bacteria |
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| 1. Nutrient Requirements 2. Metabolic Intermediate or End Products 3. Presence of Specific Enzymes |
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| 2 Tests Used to Determine the Nutrient requirements of a Bacterium |
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| 1. Citrate test 2. sugar fermentation test |
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| Citrate test -what does it determine-what is the medium-what is the indicator-how are results interpreted? |
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| -tests for the ability to use citrate as the sole source of carbon -Simon agar is used -Bromothymol Blue is the indicator -Change from green to blue (bc of pH increase) is a positive result |
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| Sugar Fermentation test -what does it determine-what is the medium-what is the indicator-how are results interpreted? |
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| -tests for Carbohydrate fermentation and gas production in a Durham tube -tube changes from green to yellow (+ result) due to decrease in pH -Bromothymol blue is the indicator -if gas is produced, it is shown by a trapped bubble |
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| 3 Tests that Determine the Metabolic Products of an Organism |
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| 1. Indole test 2. Methyl Red test 3. Vogues-Proskauer test |
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| Indole Test -what does it test for-what reagent is used? |
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| -tests for the production of indole from tryptophan (an amino acid) Tryptophase breaks down tryptophan into indole, pyruvic acid, and ammonia. Indole is what is what is being tested for, but it implactes the presence of tryptophase -the presence of indole is seen by adding Kovac's reagent, which reacts with indole and creates a red complex |
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| Methyl Red test -what does it test forwhat is the indicator? Medium-how are results interpreted? |
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| -tests for strong acid production from fermentation. Methyk red organisms produce large amounts of lactic, succinic, and acetic acid --> low pH. the produce small amount of ehtanol --> large acid:alcohol ratio -if an organism has formic hydrogenase, then equal amounts of CO2 and H2 are produced. -indicator methyl red turns red at or below pH 4.4 -MR-VP broth is used (a glucose broth) |
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| Vogues-Proskauer Test -what does it indicate-what does it detect-what medium is used? reagent-how are the results interpreted? |
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| -indicates fermentation of glucose to 2,3 butanediol and ethanol -detects presence fo acetoin -high alcohol: acid ratio -large amounts of gas produced, large CO2:H2 ratio - MR-VP medium used -add Barrits A and B --> wait 20 minutes --> pink/red= positive |
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| 3 tests that indicate the presence of specific enzymes |
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| 1. Oxidase test 2. Catalase test 3. Urease test |
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| Oxidase test -what does it determine-what dye is used? |
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| -determines if organisms have Cytochrome C. Oxidase -use a colorless dy: p-phenylenediamine dihydrochloride as an artificial electron donor -->dye is oxidized--> blue/black color |
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| Catalase test |
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| -catalase converts hydrogen peroxide to oxygen and water -usually facultative aerobes and obligate aerobes have catalase -add H2O2, ifi t bubbles, catalase is present |
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| Urease Test |
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| -determine ability of organism to hydrolyze urea -urease converts urea broth into ammonia and CO2 -hot pink color (due to pH increase) indicates positive result |
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| Cysteine Desulfurase Test |
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| -detection of H2S production -Kligler's iron agar (KIA) is used -dark precipitate indicates H2S production -if yellow |
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| phages |
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| bacterial viruses |
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| essential constituents |
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| nucleic acid and proteins- basic structure --> capsid or shell which encloses the nucleic acids (either DNA or RNA) |
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| 2 major qualities of a virus |
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| 1. possesion of its own genetic material, which, on its own, behaves as part of the host cell 2. possesion of extracellular infective state, represented by specialized onjects, the virions, which are produced in the cell under genetic control of the virus itself and serve as vehicles for introducing the viral genome into other cells |
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| plaque |
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| a clear spot on a bacterial lawn that contains no bacteria bc all the cells have been lysed |
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| 3 different viral shapes |
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| -helical: spring shaped -polyhedral: many sided -binal: polyhedral head w/ helical tail(nucleic acid in head) |
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| 3 types of T type coliphages |
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| a. T even phages: similar in geneitc constitution and serologic properties -->pyrimidine, 5-hyroxymethylcytosine replaces cytosine b. T5: resembles T even phages except has regular cytosine c. T1, T3, T7: seroligically an genetically unrelated to both one another and the T-even phages |
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| 5 Stages of phage infection |
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| 1. adsorption to specific receptor sites on bacterial cell 2. penetration of phage nucleic acid into bacterial host, protein coat remaining outside 3. intracellular development: phage replication, biosynthesis 4. maturation 5. lysis --> release |
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| Lysogeny |
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| viral nucleic acid persists in host for many generations(or indefinitely). bacterial host functions normally, viral nucleic acid is transmitted successively through many bacterial generations |
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| temperate phages |
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| bacteriophages that cause lysogeny |
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| lysogens/ lysogenic strains |
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| bacterial hosts of lysogeny |
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| prophage |
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| latent, non-infectious form which is carried in lysogenic bacteria |
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| Rhizobium |
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| gram(-) rods symbiotic organism that invades root hairs nitrogen fixing |
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| symbiosis |
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| living together |
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| 2 enzymesi nvolved in notrogen fixation |
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| transaminase & nitrogenase |
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| 2 final end products of Nitrogen fixation |
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| Amino Acids & proteins |
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| whati s the shape and gram reaction of Staphylococci? |
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| Gram (+) cocci |
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| what is the arrangement and color of Staphylococci colonies? |
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| golden/ off white clusters |
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| Is Staph tolerant of NaCl? |
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| yes, high NaCl (7.5%) |
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| where is Staph found? |
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| skin follicles and mucus membranes |
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| Staph's oxygen requirement is... |
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| facultative anaerobe |
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| pathogenic Staph |
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| Staph. aureus |
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| non-pathogenic staph |
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| Staph epidermidis and Staph saprophyticus |
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| what test is used to differentiate between pathogenic and non-pathogenic Staph? |
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| coagulase test --> (+)test = pathogenic -->coagulase converts fibrinogen to fibrin and clots plasma |
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| S. aureus causes which diseases? |
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| wound infections, pneumonia, toxic shock syndrome, food poisening |
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| S. epidermidis causes... |
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| hospital acquired infections |
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| S. autotrophyticus causes... |
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| urinary tract infections (UIT) |
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| what is the gram reaction and shape of Streptococci? |
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| Gram (+) cocci |
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| Strep is catalase... |
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| negative |
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| Staph is catalase... |
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| positive |
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| is Strep NaCl tolerant? |
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| nope (excpet in group D) |
