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283 Cards in this Set
- Front
- Back
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What is a positive result for a glucose or a lactose fermentation test?
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yellow
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what pH indicator is used in the glucose test?
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phenol red
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describe the phenol red pH indicator?
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phenol red is red in alkaline environments and yellow in an acidic environment
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What is a positive result for the MR test?
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red
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what is the pH indicator used in the MR fermentation test?
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methyl red
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describe the pH indicator methyl red
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red in an acidic environment and yellow in an alkaline environment
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What does the MR test differentiate?
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between enteric Gram negative that conduct mixed acid fermentation versus those that do not.
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What is the makeup of MRVP broth?
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glucose, peptone and dipotassium phosphate
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What is the VP test?
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Vogues-Proskauer test; differentiates enteric Gram-negative that may ferment glucose but not mixed acid fermentation so that they would not test positive for the MR test--make 2, 3-butanediol biproduct
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What does a positive result for the VP test look like?
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red
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what reagent is used for the VP test?
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Barritt's reagent; oxidizes 2, 3-butanediol to acetoin
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What are the components of Barritt's reagent?
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VP-A -->Alpha-naphthol
VP-B -->KOH |
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If an organism is MR positive, typically is it VP positive?
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No, typically a positive or negative for either one
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What is the reagent used for the catalase test?
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hydrogen peroxide
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what is a positive reaction for the catalase test?
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bubbles being produced
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what is the purpose of catalase?
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convert hydrogen peroxide to water and oxygen gas
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what organisms typically lack catalase?
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strict anaerobes and aerotolerant bacteria (ex: Streptococcus and Enterococcus)
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What is the oxidase test?
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determines if an organism uses oxygen as the final electron receptor during respiration with enzyme cytochrome oxidase that catalyzes transfer from cytochrome c in the ETC to oxygen
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What is the reagent used in the oxidase test?
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N,N,N',N'-tetramethyl-p-phenylenediamine that acts as a synthetic electron acceptor instead of oxygen
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what is indicative of a positive oxidase test?
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purple means N,N,N',N'-tetramethyl-p-phenylenediamine was reduced
negative is yellow |
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what agar is used to test the ablility of Gram negative bacteria to metabolize citrate?
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Simmon's Citrate Agar
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what are the components of Simmon's Citrate Agar?
Describe the pH indicator used? |
1.5% agar, ammonium salt(nitrogen source), citrate (carbon source) and bromthymol blue (pH indicator)
bromthymol blue (blue in alkaline environment) |
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What does a positive citrate test look like?
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blue because the ammonia produced from the utilization of the ammonium salts as a nitrate test creates an alkaline environment
green is a negative test |
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What is the urea test?
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differentiates between some gram negative enteric bacteria that produce urease to breakdown urea which is a waste-product of animal metabolism.
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What color is a positive urease test?
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Pink;
negative is yellow |
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What is the pH indicator used in the urease test?
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phenol red
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describe the phenol red indicator in the urease test?
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breakdown of urea results in ammonia which creates an alkaline environment--> red/pink
yellow in an acidic environment |
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What is the phenylalanine test?
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differentiates enteric bacteria on their ability to produce phenylpyruvic acid as a result of the phenylalanine deaminase enzyme that works by removing the amine group from phenylalanine (that's released as ammonia).
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what is the reagent used for the phenylalanine test?
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ferric chloride oxidizing agent
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what is a positive result of a PPA test?
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green after the addition of ferric chloride
negative is yellow |
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What is MacConkey's agar used for?
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selective and differential medium to detect gram-negative and lactose fermenting bacteria
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How is MacConkey selective?
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only allows for the growth of gram-negative bacteria because it contains bile salts and crystal violet dye
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How is MacConkey differential?
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distinguishes lactose fermenters vs nonfermenters
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what pH indicator is used in MacConkey agar?
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neutral red...red in an acidic environment (lactose fermenters)
yellow in an alkaline environment(nonfermenters) |
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What are components of NA?
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beef extract(nitrogen, carbs, vitamins), peptone(A.A.), agar
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what is the purpose of catalase?
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convert hydrogen peroxide to water and oxygen gas
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what organisms typically lack catalase?
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strict anaerobes and aerotolerant bacteria (ex: Streptococcus and Enterococcus)
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What is the oxidase test?
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determines if an organism uses oxygen as the final electron receptor during respiration with enzyme cytochrome oxidase that catalyzes transfer from cytochrome c in the ETC to oxygen
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What is the reagent used in the oxidase test?
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N,N,N',N'-tetramethyl-p-phenylenediamine that acts as a synthetic electron acceptor instead of oxygen
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what is indicative of a positive oxidase test?
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purple means N,N,N',N'-tetramethyl-p-phenylenediamine was reduced
negative is yellow |
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what agar is used to test the ablility of Gram negative bacteria to metabolize citrate?
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Simmon's Citrate Agar
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what are the components of Simmon's Citrate Agar?
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1.5% agar, ammonium salt(nitrogen source), citrate (carbon source) and bromthymol blue (pH indicator)
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What does a positive citrate test look like?
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blue because the ammonia produced from the utilization of the ammonium salts as a nitrate test creates an alkaline environment
green is a negative test |
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What is the urea test?
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differentiates between some gram negative enteric bacteria that produce urease to breakdown urea which is a waste-product of animal metabolism.
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What color is a positive urease test?
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Pink;
negative is yellow |
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what is the pH indicator used in MacConkey's agar?
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neutral red
-red in an acidic environment because of the lactose fermenters -yellow in an alkaline environment nonfermenters |
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what does MacConkey's agar contain that selects for Gram-negative?
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bile salts and crystal violet
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What are the components of NA?
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beef extracts (carbs, vitas, nitrogenous compounds), peptone (A.A.), agar (solidifying agent)
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How do you test an organisms oxygen requirement?
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Inoculate fluid thiogycollate medium and incubate
at surface : obligate aerobes a little below: microaerophiles at bottom: obligate anaerobes all throughout: facultative anaerobes |
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what indicator tests for the anoxic environment?
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resazurin
oxic--pink anoxic--clear |
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Gram stain components
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safranin and crystal violet
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what is the indole test?
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used to test between enteric bacteria by ability to breakdown tryptophan with the enzyme tryptophanase
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what is a positive indole test?
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red positive
yellow negative |
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What is the reagent used in the indole test?
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Kovac's reagent;
in a positive test the amyl alcohol in the reagent acts as a solvent for the the indole which then reacts with the p-dimethylaminobenzaldehyde to make a red dye. |
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awhat is tryptophan broken down into?
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indole, pyruvic acid and ammonia
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What is Kligler's Iron Agar?
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diffentiates bacteria based on ability to ferment lactose and dextrose, free sulfides and whether gas is produced
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what indicates free sulfides by the Kligler's Iron Agar?
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black in the butt
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What does a negative test on Kligler's Iron agar look like?
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red
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what does positive iron agar test look like?
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lactose fermenters look yellow
gas fermenters by displacement dextrose fermenters look yellow too (all lactose fermenters are dextrose fermenters also) |
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what pH indicator does Kligler's Iron Agar contain?
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phenol red
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describe the phenol red pH indicator?
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phenol red is red in an alkaline environment and yellow in an acidic environment (fermenters)
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Nitrate test
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tests facultative anaerobes ability to reduce nitrate; tests for either gas or nitrite
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what is a positive nitrate test?
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dark red
negative is clear |
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what two reagents are used for the nitrate reduction test?
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sulfanilic acid and dimethyl-alpha-naphthylamine
if positive nitrite will react with both of these to produce a dark red color negative means no nitrate reduced or nitrite was not the reduced form |
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starch agar
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test metabolism of starch
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what is the reagent used as starch agar?
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gram's iodine--> reacts and makes a dark blue color
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what is a positive starch test?
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clear area formed around growth because amylase present to breakdown starch
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what is a negativce starch test?
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dark blue because unable to breakdown starch
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What physical parameters did we test for their affect on Bacterial growth?
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1. Temperature
2. Salt Concentration 3. UV light 4. pH |
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psychrophile
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-5C to 20C
in supercooled H2O of Arctic/Anarctica |
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example of a psychrophile
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Listeria monocytogenes
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Where is Listeria moncytogenes found?
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dairy products
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mesophiles
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20C-50C
these are most bacteria that we handle in class |
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what is the optimum temperature for most pathogens?
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35C-40C
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thermophiles
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50C-80C
soils where midday temp > 50C or compost wher fermentation causes temp > 60-65C |
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hyperthermophiles
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>80C
ex: by volcanos |
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ex of a mesophile
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Proteus and Pseudomonas
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psychotrophs
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4C (refrigerator temperature)
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where does maximum enzyme activity occur?
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at optimum temperature
**above maximum enzymes denature and lose activity |
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what organism produces a red pigment at 25C?
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Serratia marcescens
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What organism produces a yellow pigment at 25C?
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Micrococcus luteus
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What 3 organisms did we test for environmental effects on growth?
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Serratia marcescens, Staphylococcus aureus, Escherichia coli
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At what temperatures did we grow the microorgansims?
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5, 25, 37, 45
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What organism grew at 25C
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S. marcescens
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What organism grew at 37C?
What organism grew at 45C? |
S. marcescens, S. aureus and E. coli
??? |
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neutrophiles?
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grow near neutral pH
most bacteria w/in a range of 2-3 units |
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acidophiles?
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acidic
ex: Thiobacillus thiooxidans |
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alkaliphiles?
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basic
soda lakes/high carbonate soils ex: many Bacillus |
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what pH values did we grow microorganisms?
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3, 5, 7, 9
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what affect does pH have on the cell?
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the [H+] affects proteins and other charged molecules
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what occurs at higher pH values than optimum when it concerns the charged molecules?
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adversely affected and precipitate out of the solution
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What are the 3 organisms that we tested for PH affects?
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Escherichia coli, Staphylococcus aureus, Bacillus subtilis
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What pH did the microorganisms grow at optimum?
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7-->E. coli, B. subtilis, S. auresu
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osmosis
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water diffuses from low solute concentration to high solute concentration
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plasmolysis
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hypertonic environment causes water to diffuse out of cytoplasm
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at what water activity do most organisms grow?
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0.9-1.0
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halophiles
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15-30% NaCl
salt lakes and brine solutions, salted fish |
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halotolerant
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capable of growth in moderate salt concentrations
ex: Staphylococcus aureus |
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osmophiles
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grow in environment where sugar concentrations are excessive
ex: Xeromyces |
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what salt concentrations did we test?
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0.5%, 5%, 10% and 15%
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What organisms did we grow on the salt concentrations?
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S. aureus, E. coli, B. subtilis
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What grew at 0.5% salt concentration?
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all grew because this is typical concentration in media
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What grew at 5% salt concentration?
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Staphylococcus aureus
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What grew at 10% salt concentration?
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Staphylococcus aureus
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What grew at 15% salt concentration?
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NONE
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Why are Staphylococcus suitable to grow on skin?
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because its halotolerant and can tolerate up to 11% NaCl concentration
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What is the effect of UV radiation on organism?
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causes pyrimidine dimers (covalent bond) between 2 adjacent thymine or cytosine molecules in a DNA strand
cause the DNA molecule to become deformed so that DNA polymerase cannot replicate DNA strands past the site of dimer formation nor can genes past this point be transcribed |
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what is UV light?
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nonionizing short wavelength between 4-400nm
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What organisms did we test for UV radiation?
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S. aureus and B. subtilis
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what organism is UV resistant?
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Bacillus subtilis
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Why is B. subtilis UV resistant?
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because it forms endospores
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What is the optimum wavelength for UV radiation to work?
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260nm because DNA absorbs maximally at this wavelength
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what do the killing properties of UV radiation depend on?
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time and presence of materials that'll block the radiation
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what time exposure did we use for the UV radiation test?
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0, 5, 10, 30
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What grew at 0min?
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both S. aureus and B. subtilis
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what grew at 5-30min?
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S. aureus didn't grow
B. subtilis |
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why didn't Staphylococcus aureus grow?
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Because vegetative cells are more prone to UV treatment
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antiseptic
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used to destroy pathogens on living tissues
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What organisms did we test for UV radiation?
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S. aureus and B. subtilis
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what organism is UV resistant?
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Bacillus subtilis
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Why is B. subtilis UV resistant?
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because it forms endospores
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What is the optimum wavelength for UV radiation to work?
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260nm because DNA absorbs maximally at this wavelength
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what do the killing properties of UV radiation depend on?
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time and presence of materials that'll block the radiation
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what time exposure did we use for the UV radiation test?
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0, 5, 10, 30
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What grew at 0min?
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both S. aureus and B. subtilis
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what grew at 5-30min?
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S. aureus didn't grow
B. subtilis |
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why didn't Staphylococcus aureus grow?
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Because vegetative cells are more prone to UV treatment
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antiseptic
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used to destroy pathogens on living tissues
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how did we test an antiseptic?
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took loopful of bacteria and placed in a dilution blank created lawn of bacteria and took punhciout os bleach iodine and alcohol
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which antiseptic worked the best?
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bleach
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how did we test the effects of handwashing?
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fingerprints with alcohol, unwashed, hand sanitizer and handwashed
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what medium did we use to test the effect of handwashing?
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Brain Heart Infusion Agar
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What agar was used to test antibiotics?
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Mueller Hinton Agar
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give some examples of antibiotics?
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kanamyocin, vancomycin, ampicillin, streptomycin, tetracycline
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what was the results of the handwashing experiment?
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dirtiest --> cleanest
unwashed, alcohol, hand wash, sanitizer |
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what do we measure the zone of inhibition in?
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millimeter
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what is on the disk used for the antibiotic test?
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mininum amount to kill
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What test was used for antibiotic sensitivity testing?
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Kirby-Bauer Method
determines how effective antibiotics are to certain bacteria |
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antimicrobials
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kill/inhibit microorgs
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antibiotics
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antimicrobials made by microorganism to inhibit/kill other microorgs
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what are antibiotics made from?
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fungus/molds
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antibiotics
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chemotherapeutics agents of low molecular weight produced by microorganisms
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semi synthetics
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chem altered antibiotics to be more effective
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synthetics
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antimicrobials not made by microorganisms but are chemically made in a lab
ex: sulfa drugs (used before penicillin) |
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what organisms were used in the antimicrobial test?
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S. aureus, E. coli, P. vulgaris, P. aeruginosa
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MIC
|
minimum inhibitory concentration
lowest concentration of antimicrobial that'll inhibit growth of microorg after over night incubation |
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who is credited with discovering the businesses of hand-scrubbing?
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Semmelweis (Vienna); childbirth fever
had physicians disinfect with bleach |
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nosocomial
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hospital aquired infection
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normal bacteria of skin
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diptheroids, staphylococci, yeast/fungi
|
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diptheroids
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gram+; nonpathogenic
live in hair follicles and break down sebum (oily secretion that stops dessication) |
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staphylococci
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inhibits pathogens presence
ex: nonpathogenic |
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yeast/fungi
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typ. nonpathogenic, some opportunistic
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zones of inhibition ranges
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resistant, intermediate, sensitive
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bacteriostatic
bacteriocidal |
limit growth
kill organisms |
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why do we examine water for bacteria?
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look at coliforms which would indicate fecal contamination
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why do we specifically test for E. coli?
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in intestines, not in soil/H2O, easily ID'd by tests, not as fastidious
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coliforms
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Ex: E. coli, E. aerogenes
gram neg, facultative anaerboes, no spores formed, ferment lactose and make gas in 48 hours |
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What are 3 tests used to verify coliform presence in H2O?
|
1. presumptive test
2. confirmed test 3. completed test |
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presumptive test?
|
inoculate with lactose borth and look at gas production
2 groups of 3 single strength 1 group of 3 double strength |
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confirmed test?
|
Eosin Methylene Blue medium
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completed test?
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look at gas produxn and gram negative
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eosin methylene blue?
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selective for gram negative and differential for lactose fermenting
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how do those that ferment lactose look?
|
purplish
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how does E. coli look?
|
metallic green sheen
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what tubes did we plate concerning the examination of water?
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if tubes were yellow that means they fermented lactose and therefore microorganisms grew
plated on EMB |
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what bacteria were purple on EMB?
green on EMB? |
Enterobacter aerogenes
Escherichia coli |
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what is the danger zone concerning bacteria?
|
40-140F
|
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how keep foods out of danger zone?
|
keep cold food cold and hot fodd hot
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what temp store food in fridge?
what temp store food in freezer? |
40F and below
0F and below |
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what temp cook food to?
|
160F and keep @ 140F
|
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do bacteria grow in fridge?
|
yes but growth is slowed
|
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food microbiology
|
the study of microorganisms that inhibit, create or contaminate food and cause spoilage
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how does bacteria get into food?
|
on raw foods because gets contaminated by workers
cross contamination (bacteria for rwa food, meat juices, other contaminatied products or bad personal hygeine) |
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campylobacter jejuni
|
chicken and eggs
|
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Clostridium botulinium
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canned goods, anaerobic
|
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Clostridium perfringens
|
poorly made meat and poultry;
gas gangrene |
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E. coli O157:H7
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raw foods; normal intestinal flora
|
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Salmonella
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chicken eggs
over 1600 types |
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Streptococcus A
|
S. aureus
|
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Listeria monocytogenes
|
grow in fridges
|
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Shigella
|
NO good Shigella
over 30 types |
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spectrophotometer
|
measures OD/absorbance of a culture by passing light through a cell suspension and detects the unscattered light that emerges
|
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Coagulase test
|
a test specific for Staphylococcus aureus because coagulase is an enzyme in S. aureus that changes fibrinogen to fibrin promoting blood clotting
|
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what does coagulase test help you do?
|
distinguish between different types of Staphylococcus
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what is the only coagulase positive organism?
|
Staphylococcus aureus
|
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besides coagulase test, what is a way to test for staphylococcus?
|
Mannitol sugar agar plate
|
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what is a positive mannitol sugar agar plate look like?
|
yellow
pink in a negative test |
|
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describe how coagulase can be a virulence facter?
|
coagulated blood around the bacteria can protect them from the immune system
|
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are coagulase negative strains pathogenic?
|
yes some are. the presence or absence of coagulase does not grant pathogenicity
|
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What does a positive coagulase test look like?
|
clumping is evident if on slide
if in tube, cloudiness is in the bottom |
|
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what 2 bacteria did we test for coagulase?
|
Staphylococcus aureus
Micrococcus luteus |
|
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give an example of a coagulase negative organism?
|
Micrococcus luteus
|
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give an example of a coagulase positive organism?
|
Staphylococcus aureus
|
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in the bacterial examination of water, what is the presumptive test?
|
a positive result in lactose broth (either gas is produced/or change to yellow) making you assume that a coliform is present
|
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in the bacterial examination of water, what is the confirmed test?
|
test those tubes which had a positive lactose broth test by streaking on EMB media
if metallic sheen or pink nucleated colony then there is a coliform |
|
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what 2 coliforms did we say were possible?
|
Enterobacter aerogenes and or Escherichia coli
|
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what is a completed test in the bacterial examination of water?
|
combination of the presumptive test and the confirmed test. Also gram stain
|
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plasmid
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tiny circular extrachromosomal strands of DNA that contain a few genes that exist in the cytoplasm and replicate on their own
|
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are plasmids independent life forms?
|
yes because they replicate on their own
|
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where do plasmids naturally occur?
|
bacteria
sometimes found in euk. cells |
|
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what is the function of a plasmid?
|
1. provide DNA (extra info not essential for cell survival)
ex: encode for resistance, metabolic functions, enhance virulence and produce toxins **only needed under special circumstances |
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how are plasmids used?
|
genetic engineering (ex: human insulin gene has been isolated and inserted into E. coli to study diabetes)
**insert foreihgn DNA into bacterial plasmids to express a gene of interest |
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what are plasmids used in genetic engineering called?
|
vectors
|
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what is a vector
|
any vehicle used to transfer "foreign" DNA to another
|
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what plasmid will we isolate?
|
Puc19 (a common DNA vector from E. coli)
|
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what 3 steps does isolation involve?
|
1. breaking the C.W. and denaturation of cellular proteins and chromosomal DNA
2. centrifugation to separate the unwanted particles so you're left with plasmid DNA and RNA 3. RNAse treatment to remove RNA |
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What does lysis solution 1 do?
|
breaks C.W. and leaves C.M. intact
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what does lysis solution 2 do?
|
break C.M and get rid of genomic DNA
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what does lysis solution 3 do?
|
precipitates DNA
|
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how do we visualize plasmid DNA?
|
agarose gel electrophoresis that separates DNA molecules based on size
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what is used to stain DNA?
|
Ethidium Bromide (carcinogen)
|
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how does Ethidium Bromide stain the DNA?
|
intercalates the DNA and is visible under UV light
|
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what buffer is added to the electrophoresis chamber before you run the gel?
|
TBE-Tris/Borate/EDTA
|
|
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when was Taq polymerase isolated?
|
1965 from Thermus aquaticus by Brock
|
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who developed PCR?
|
Kary Mullis in 1980s
|
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what is the significance of Taq polymerase?
|
able to withstand 95C that is needed to denature DNA through cycles so that DNA synthesis can still occur
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what is PCR?
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polymerase chain reaction; sensitive means to amplify large quantities of DNA
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5 materials needed for PCR?
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template DNA
DNA nucleotides primer Taq DNA polymerase dNTPs |
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major steps of PCR?
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deturation (94)
annealing (54) extention (72) repeat 30-40 times |
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denaturation purpose
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break open DNA
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annealing purpose
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anneal primers to ssDNA template
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extention purpose
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bases (complementary to the template) are coupled tothe primer on the 3' side.
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what way does polymerase add dNTPs to?
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5' to 3'; so its reading 3' to 5'
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What organism produces the yellow pigment?
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Micrococcus luteus
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name of the S. marcescens pigment?
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prodigiosin
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what is the normal temperature that we incubate bacteria at?
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37C
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hypotonic
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less concentration---water flows into cell
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isotonic
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same concentration
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hypertonic
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higher concentration--so water flow out of cell.
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osmosis
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movement of water
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halophiles
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15-30% NaCl to grow/maintain C.W.
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halotolerant
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tolerate moderate salt concentration
ex: Staphylococcus aureus up to 11% NaCl |
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plasmolysis
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contraction of cells within plants because of loss of water to osmosis; plasma membrane pulls away from cell wall
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optimum water activity for most bacteria?
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0.9-1.00
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UV light
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4-400nm wavelength of radiation
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what does UV light to to DNA?
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-causes pyrimidine dimers to form (covalent bond between 2 adjacent thymine/cytosine)
-dimers casue the DNA molecule to become deformed so that DNA polymerase can't replicate past the site of dimer formation so genes not transcribed |
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Why did we use Bacillus cereus in UV?
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because of endospores
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germicidal
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a disinfectant; kills microorganisms
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what is the importance of using 260nm?
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this is the most germicidal wavelength becasue DNA maximally absorbs at this wavelength
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What equation is used to measure pH?
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-log([H+])
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opitmum pH for most bacteria?
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7 (neutral)
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how does pH affect organism?
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Hydrogen ion concentration affects proteins and other charged molecules in the cell.
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what happens if pH values exceed optimum?
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solubility of charged molecules can be adversely affected and molecules can precipitate out of solution
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what's an example of the effects of pH?
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charge of A.A. in proteins changed and enzymes are denatured and lose activity
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antiseptic examples?
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alcohol, iodine, bleach
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antibiotic examples?
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tetracycline, streptomycin, ampicillin, vancomycin
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bacteriostatic
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inhibits growth but doesn't kill
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sterilants
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destroy all microbial life (including endospores)
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sporocides
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destroys all microbial life (including endospores)
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bacteriocidal
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kill bacterial cell
ex: heat |
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sanitizers
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reduce microbial numbers to a safe level but don't completely eliminate all microbes
ex: hand sanitizer (99.999% lol) |
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antibiotic
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substance produced by a microorganism that inhibits the growth of another
ex: streptomycin |
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what method did we use to test antibiotic sensitivity?
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Kirby-Bauer
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describe the medium used for antibiotic sensitivity?
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Mueller-Hinton II agar
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describe the Kirby-Bauer method?
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inoculate agar plate by swabbing with diluted sample, use sterile forceps to place discs with antibiotic on them (press down), incubate and measure zone of inhibition to determine resistant, intermediate or sensitive
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antimicrobials
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compounds that kill or inhibit microorganisms
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semi-synthetics
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antibiotics chemically alterd to make them more effective
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synthetics
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antimicrobials chemical synthesized in the lab and aren't the result of microbial synthesis
ex: sulfa drugs |
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zone of inhibition
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diameter around the disk where no growth occurs
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resistant
intermediate sensitive |
as sensitivity increases, zone of inhibition increases
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how did we evaluate antiseptics?
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can be applied to living tissue
-don't destroy endospores ex:bleach, 70% alcohol |
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what are some infectious diseases that can be spread in water?
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Vibrio cholerae (Cholera)
Salmonella typhi (typhoid fever) Shigella dysenteriae (dysentery) |
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What bacteria are used to indicate fecal contamination?
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Escherichia coli
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why use E. coli?
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1. in intestings of humans and warm blooded animals not ins soil/water
2. easily identified with microbiological tests 3. not as fastidious so it survives longer in water samples |
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coliforms
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gram neg
facultative anaerobes non-endospores ferment lactose making acid/gas in 48hours at 35C |
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2 examples of coliforms
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Escherichia coli
Enterobacter aerogenes |
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how did we conduct the presumptive test?
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inoculated 9 tubes of lactose broth and durham tubes with 10ml, 1ml and 0.1ml of sample water respectively, incubated and looked at results
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what was a positive presumptive test
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the production of gas/yellow change
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what is the confirmed test
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inoculate/incubate plate of EMB agar
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EMB agar
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selective for coliforms and differential between the coliforms
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how does e. coli look on EMB
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metallic green sheen and small colonies
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how does e. aerogenes look on EMB
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purple colonies larger
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what is MPN
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most probable number
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MPN is measured in?
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MPN index/ 100ml
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how does bacteria get into food?
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1. from workers
2. cross contamination |
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what bacteria are responsible for foodborne illnesses?
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E. coli 0157:H7
Clostridium botulinum Campylobacter Shigella |
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good bacteria example
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lactobacillus (in yogurt, cheese, fights infection)
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bad bacteria example
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Shigella (anything that causes foodborne illness)
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What type of bacteria grow at refridgerator temps?
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psychrophiles Listeria monocytogenes
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food microbiology
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the study of microorgs that inhabit create or contaminate food and cause spoilage
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how do you put CFUs into sig figs?
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multiply number of bacteria times the inverse of the dilution factor
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Spirit blue agar
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see whether bacteria produces lipase.
It contains nutrients, emulsified lipids and the dye spirit blue. Clearing of the emulsion is a positive indicator of lipase. |
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Mannitol Sugar Agar
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differentiates pathogenic/nonpathogenic staphylococci as it contains a high salt concentration, mannitol, and phenol red. Those that are pathogenic ferment lactose and lower the pH change the color to yellow
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