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114 Cards in this Set
- Front
- Back
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what is the streak plate technique?
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bacterial mixture is transferred to the edge of an agar plate with an inoculating loop and then streaked in patterns
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what is the key principle of the streak plate technique?
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a dilution gradient is established on the surface and confluent growth occurs on the plate where the cells are not so seperated
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what is selective media?
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favor the growth of particular organisms such as crystal violet liking gram negative bacteria
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what is differential media?
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distinguish between different groups of bacteria and permit identification of microorganisms based on biological characteristics
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in the streak plate technique how are organisms diluted and spread out to form individual colonies?
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moving back and forth and flaming in between. this dilutes the cell colonies because they are spread out
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which area of the streak plate held the most growth? the least?
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first, fourth
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why can a single colony on a plate be used to start a pure culture?
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all the organisms on the colony came from that one parent
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how can a streak plate become contaminated?
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not flaming the loop, leaving lid off too long
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what are obligate anaerobes?
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microorgansims that only grow in the presence of oxygen
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what is an example of an obligate anaerobe?
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pseudomonas aeruginosa
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what are obligate aerobes?
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only grow where there is oxygen
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what is an example of a obligate anaerobe?
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clostridium sporogenus
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what is an example of a faculative anaerobe?
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ecoli
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what are faculative anaerobes?
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growth happens with either oxygen or no oxygen but better with
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what are aerotolerant anaerobes?
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they dont use oxygen but are not harmed by it
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what are microaerophiles?
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microorganisms that require a small amount of 0xygen for normal growth but are inhibited by oxygen at a normal atmospheric tension
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what is the gaspak anaerobic system?
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hydrogen and co2 are generated by an envelope after adding water to chemicals. some palladium pellets in the chamber lid catalyze the formation of water from hydrogen and oxygen thereby removing oxygen from the chamber
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in the gaspak plates what showed no growth? why?
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p. aeroginosa showed no growth, thus being because there was no oxygen and p. aero is an obligate aerobe
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in the oxydish, what showed no growth? why?
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clostridium sporogenus, because it cannot handle oxygen
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what are oxydish?
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contains an inner ring that forms a tight seal with the agar surface. oxygen is reduced in the agar medium and trapped headspace in the dish
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how does the thioglycollate medium work?
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has to do with sulfhydro groups. has to do with binding to oxygen
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of the methods used in creating an anaerobic environment, which works the best and why?
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the plates because they eliminate oxygen alot easier
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what are cfu's?
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colony forming units. they will develop into single discrete colonies
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what is the standard plate count method?
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diluting a sample with a sterile saline until the bacteria are dilute enough to count accurately
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what is the difference between %t and absorbance?
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they are the inverse of each other. when t% is high then absorbance is low
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why is the viable plate count technique considerd to be an indirect measurement of cell density whereas the turbidemetry method is not a count at all?
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viable plate count is indirect because youre counting colonies. turbidemetry is biomass in the tube
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why is it necessary to shake the tube 25 times?
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to get an even dispension
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define biomass
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amount of organic material in cellular form at any given time
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what is an advantage of the spectrophotometric determination of bacterial numbers? disadvantages?
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its fast...but its bad because you have to have a standarc curve done already, nothing is absorbed until you have 10 million cells and all biomass is recorded in the reading
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define fermentation
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anaerobic production of organic products via electron transfer from one organic molecule to another
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do all micro organisms produce the same end product from pyruvate?
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no there are different products
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what is the purpose of phenol red or bromcresol purple in the fermentation tube?
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determines if the organism is acidic or basic..yellow=acidic and red= basic
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what is the function of the durham tube in the fermentation tube?
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collects gas byproduct
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what are some of the metabolic end products produced by the different microorganisms used in this experiement?
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lactic acid, ethonol and co2
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what is the color of phenol red at an acid pH?
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yellow
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what is the function of beta galactosidase?
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breaks down lactose into glucose and galactose
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what is a protein?
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chain of amino acids
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what is hydrolysis?
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splitting apart a molecule using water
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what is caesin?
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large milk protein found in the curd portion
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what is a protease?
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enzyme that breaks down protein into amino acids
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what is an amino acid?
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building block of protein that contains atleast an amino group and one carboxly group
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what is a peptide bond?
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2 amino acids bound together
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what is protelysis?
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breaking of proteins by hydrolysis
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how can tsa that contains milk be used to determine proteolysis?
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looking for clearing around the bacteria
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why are some bacteria able to grow on plate agar count that contains milk even thouse they do not produce any protease?
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they use other components in the milk
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what happens to the durham tube durnig the autoclave?
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air is expelled from the tube and they become filled with the medium, if gas is produced the liquid inside the tube will form a bubble
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what can be used instead of lactose that is considered an artificial substrate?
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onpg
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onpg upon hydrolysis yields what?
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o-nitrophenol, its yellow in alkaline solution
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define the function of hydrolysis
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breakdown of complex organic molecules into smaller ones with water
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describe the chemistry of starch hydrolysis
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amylose and amylopectin are rapidly hydrolyzed by certain bacteria using their a-amylases to yeild dextrins, maltose, and glucose
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the chemical used to detect microbial starch hydrolysis on starch plates is what?
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grams iodine
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what does starch hydrolysis by a bacterium indicate?
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that is has one enzyme (alpha enzyme)
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amylase is an enzyme that attacks starch. what is the smallest product of this hydrolysis?
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glucose
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how is it possible that bacteria may grow heavily on starch agar but not produce an alpha amylase?
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use beef extract to get nutrients
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what are the ingredients of starch agar?
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starch, agar, beef extract and water
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why is milk white?
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it has caesin in it
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why was sterile skim milk used in the experiment?
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for no contamination and whole milk curdles a lot more than skim does
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what is caesin?
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large milk protein incapable of permeating the plasma membrane of bacteria, therefore it must be degraded into amino acids before bacteria can use it as their source of energy
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what is a zone of proteolysis?
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a clear area surrounding the colony
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how do you know if the zone of proteolysis is positve?
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theres a clearing thats cloudy. negative if medium surroundingnthe bacterial colony remains opaque
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how can gelatind hydrolysis be beneficial to some bacteria?
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if they breakdown connective tissue they are able to spread
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what is gelatin?
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soluable mixture of polypeptides derived from callogen thats been boiled
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what is unique about gelatin at 35 degrees versus 5 degrees?
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35 is liquid 5 is solid
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can gelatin hydrolysis be correlated with the pathogenicity of a bacterium?
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yes, because its organisms can spread throughout the host and be liquified
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why is gelatin liquefied in the prescence of gelatinase?
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amino acids get broken apart (peptide bonds) and do not go back together
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what is the importance of catalase to certain bacteria?
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neutralize hydrogen peroxide
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what 2 groups of bacteria can be differentiated with the catalase test?
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staph+micrococcus (+)
enterococci+streptococci (-) |
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what are the 3 products that result when flavoproteins reduce o2?
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h2o2 o2- and h2o
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what is the normal product of flavoprotein reducing o2?
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h20
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what are bacteria that produce catalase?
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staph, micrococcus, ecoli
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what is the substrate of the catalase reaction?
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hydrogen peroxide or h2o2
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what is the function of the methalyene blue in the reductase test for milk quality?
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with oxygen methalyene blue is blue and considered to be oxidized. if its clear then theres no oxygen
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why does milk sour when its not refridgerated?
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more bacteria means acid production
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how can a milk sample be contaminated by humans?
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coughing, sneezing, breathing, pooping (ecoli)
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why is milk pastuerized and not sterilized?
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becomes very bland tasting
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as a bacteriological medium, how does milk differ from water?
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it had more nutrients
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what are some bacteria normally found in milk
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streptococcus, brucella, lactobacillus, listeria, micobacterium
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what is pasteurization?
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means of processing raw milk before it is distributed to assure that it is relativelty free of bacteria and safe for human consumption
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what is a common method of pastuerization?
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heating to 71.6 degrees c for 15 seconds or 161 f
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for the pglo experiment, what was the animal it invovled?
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jellyfish
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for the pglo experiment what was it soaked in?
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calcium chloride
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in bacterial colonies, what are some of the characteristics?
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form, elevation and margin
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whats an example of form?
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circular
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whats an example of elevation?
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flat
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whats an example of margin?
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entire
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what is a bacterial colony?
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A group or cluster of bacteria derived from one common bacteria.
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what is the purpose of the ethanol in the spread-plate technique?
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ethanol is used to sterilise the glass spreader (when used in conjunction with the flame) between spreads
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what is the purpose of the spread-plate technique?
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to grow and isolate colonies of bacteria
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why are petri plates labeled at the bottom?
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to minimize contamination. So, it is easier to read the label on the bottom. Also, if the lids are accidentally exchanged, it will be less of a problem.
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microbicidal means what?
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to kill
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microbiostatic means what?
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to inhibit
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efficiency of a chemical is determined by what?
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its ability to determicrobial growth
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what is the phenol coefficient
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calculated by dividing the highest dilution of the antimicrobial of interest by the highest dilution of phenol
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the highest dilution of microbial interest does what?
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kills all organisms after incubation for 10 minutes but not not after 5
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chemicals that have a phenol coeffecient greater than 1 are:
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more effective that phenol
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what are some limitations of a test such as you performed on the evaluation of a disinfectant?
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evaporation, concentration of chemical (dilution) and gram positive or negative
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what are some characteristics of a good disinfectant?
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kill all microorganisms in 10 mnutes or less, easy to use, inexpensive, safe for humans, not damage surfaces
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a 1/100 dilution of phenol kills. the disinfectant diluted is 1/500. what is the phenol coefficent of the disinfectant?
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500/100= 5 (times more effective than phenol)
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what is the difference between microbicidal and microbiostatic?
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microbicidal means to kill and microbiostatic means to inhibit
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what physical factors can influence the activity of a disinfectant?
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ph, temp, humidity
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why do microorganisms differ in their response to disinfectants?
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gram positive or negative cell wall differences
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how can you determine whether the zone of inhibition is due to death or to inhibition of a bacterium?
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take a loop sample in the zon and streak a plate to see if anything grows
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what factors must be carefully controlled in the kirby-bauer method?
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amount of bacteria used, period of incubation, diffusion rate of antibiotic, concentration of antibiotic on the disk
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in which phase is a bacterium most sensitive to an antibiotic?
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log phase: lots of cells are getting new proteins and cell walls
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what is the difference between an antibiotic and an antimicrobic?
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antibiotic: substance produced by microorganisms against microorganisms
antimicrobic: manmade products affective against microrganisms |
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what are some reasons bacteria are becoming more resistant to antibiotics?
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if you try to get by without them you will be more likely not to be overexposed when you really need it
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what is the kirby bauer method
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antibiotics are impregnated onto paper disks and then placed on a seeded agar plate using forceps
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what are antibiotic susceptibility patterns?
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antibiograms
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what is 10^3
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1000
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what is 10^-3
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0.001
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what is 10^-2 as a fraction
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1/100
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55 colonies were counted in a 10^-5 dilution plate. what is the number of bacteria in the original sample?
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5.5 x 10^6
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what is the kirby bauer method
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antibiotics are impregnated onto paper disks and then placed on a seeded agar plate using forceps
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what are antibiotic susceptibility patterns?
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antibiograms
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