Micro202 exam 2 – Flashcards
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| What is the difference of one pH unit? |
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| One pH unit means ten-fold increase or decrease in H+ concentration. So, for every DECREASE of one unit pH, the H+ concentration INCREASES by 10-fold. |
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| Are bacteria or fungi more tolerant of high acid environments? |
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| fungi |
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| What is the purpose of using low pH media ? |
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| in order to select for fungi, we need to manipulate the living environment so we can inhibit the growth of bacteria. |
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| Who the is culprit for the spoilage of HIGH ACID foods? like fruit |
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| fungi |
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| How can a microbe change the pH of its own environment? |
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| If it is busy decomposing proteins peptones or tryptones, then the ammonia produced by the removal of amino groups from amino acids can raise the pH, increasing the alkalinity of the environment. |
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| What is the difference of one pH unit? |
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| One pH unit means ten-fold increase or decrease in H+ concentration. So, for every DECREASE of one unit pH, the H+ concentration INCREASES by 10-fold. |
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| Are bacteria or fungi more tolerant of high acid environments? |
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| fungi |
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| What is the purpose of using low pH media ? |
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| in order to select for fungi, we need to manipulate the living environment so we can inhibit the growth of bacteria. |
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| Who the is culprit for the spoilage of HIGH ACID foods? like fruit |
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| fungi |
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| How can a microbe change the pH of its own environment? |
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| If it is busy decomposing proteins peptones or tryptones, then the ammonia produced by the removal of amino groups from amino acids can raise the pH, increasing the alkalinity of the environment. |
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| How do buffers work? |
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| they bind to the H+ or the OH- ions, removing them from solution and preventing them from contributing to the pH of the solution. |
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| What is an example of a bacterium that uses lactic acid fermentation? |
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| E. faecalis |
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| how does E. faecalis inhibit its own growth? |
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| it produces lactic acid which causes an increase in H+ concentration and lowers the pH, which ultimately inhibits cell growth |
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| What instrument do we use to measure turbidity? |
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| Spectronic 20 |
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| what are the two types of toxic oxygen species? |
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| super oxide O2- and H2O2 hydrogen peroxide |
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| what are the enzymes used by a cell to metabolize toxic forms of oxygen? |
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| superoxide dismutase; catalase |
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| how does superoxide dismutase work? |
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| It converts super oxide to H2O2 and thencatalase converts H2O2 to H20 and O2 |
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| strict aerobe |
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| must have oxygen to grow and multiply...ex. micrococcus |
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| microaerophilic |
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| require oxygen, but grow best at reduced oxygen concentrations...20% or below. ex. heliobacter pylori |
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| what's an example of a bacterium that would live in the stomach? |
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| heliobacter pylori |
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| facultative anaerobe |
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| can use oxygen if available, but don't need it to grow and divide. ex. E. coli and staphylococcus |
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| aerotolerant |
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| incapable of using oxygen...they rely on metabolic pathways such as fermentation pathways to produce ATP...ex. streptococcus and Enterococcus |
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| strict anaerobe |
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| lack oxygen detoxifying enzymes like catalase and superoxide dismutase...they are unable to grow in the presence of oxygen. e.x Clostridium C. perfrigens |
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| how can gas gangrene be cured? |
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| C. perfrigens causes a very dangerous, life-threatening type of wound infection that can be killed if oxygen's forced into the site of infection |
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| If an environment has a positive or high ORP value, what does that mean? |
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| The amount of free O2 in the environment is high. |
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| what's an example of something that oxidizes another? |
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| O2...has high affinity for electrons. |
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| what's an example of something that reduces another? |
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| thioglycollate...have LOW affinity for electrons |
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| an oxidizing environment would prevent the growth of what kind of microbes ? |
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| strict anaerobes and aerotolerants would not grow as well in comparison to growing in a reducing environment |
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| What's the best way to remove oxygen from media so that anaerobic bacteria can grow? |
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| boiling and sealing. |
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| What are examples of reducing agents? What do they do? |
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| thioglycollate//cysteine...their SH group readily donates electrons and protons to other molecules |
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| how do we know that reducing agents are doing their job? |
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| resazarin will be colorless when it is in the fully reduced state, and it will turn pink as it becomes less reduced and more oxidized. |
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| how is oxygen removed from a sealed chamber? |
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| flow nitrogen or CO2 though the hood. |
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| What is a GasPak? |
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| it's a packet added to a Brewer Jar that contains soduim bicarbonate citric acid, and a catalyst. It creates an environment that is ideal for the growth of strict anaerobes. |
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| How does a GasPak work? |
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| 1. water reaches sodium carbonate and citric acid tablet and CO2 is released. This is good because many strict anaerobes grow best in high CO2 environments. 2. water reacts with sodium borohydride and H2 gas is released, which combies with free O2 in the air, and creates anaerobic environment. |
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| What is methylene blue? |
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| direct stain//redox indicator. .if oxygen is present, and methylene blue is oxidized, then it will be blue in color, but in the absence of oxygen, the methylene blue will be reduced and will be colorless. |
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| What does a blue methylene strip inside a Brewer jar mean? |
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| too much free oxygen entering the jar. |
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| -static agents |
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| indicates that the chemical in question will inhibit or stop microbial growth, but it may not kill the cells. |
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| -cidal agents |
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| the chemical in question will kill microorganisms |
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| are "-cidal" agents able to sterilize? |
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| yes, depending on the length of time and how it is used. ex. formaldehyde. |
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| disinfectant |
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| used to describe chemicals applied to non-living or inanimate surfaces. all of these agents are "-cidal" agents. |
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| antiseptics |
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| used to describe chemicals applied to living tissue |
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| which one is more toxic? disinfectants or antiseptics? |
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| disinfectants...but anti-septics still have a killing effect on microorganisms |
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| What are the 6 factors that anti-microbial activity depends upon? |
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| 1) pH 2) temperature 3) solubility of the agent 4) interactions with other chemicals in the environment 5) initial size of the microbial populations 6) types of microbes present |
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| phenol coefficient |
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| a value that can be determined for each type of chemical agent by comparing the effectiveness of the test chemical against the potency of a standard disinfectant, phenol. (must be done against gram positive and gram negative) |
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| How does the phenol coefficient assay work? |
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| the test chemical is repeatedly diluted until the dilution is so great that the agent is no longer able to kill the bacteria. |
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| what is the maximum effective dilution? |
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| The greatest dilution that did in fact kill the test bacteria is recorded as the "maximum effective dilution." |
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| How do you calculate the Phenol Coefficient? |
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| PC= (reciprocal of max effective dilution of disinfectant)/ (phenol) 100 = PC |
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| What is the average phenol coefficients of disinfectants today? |
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| most are more toxic than phenol...have values from 10 to 200 |
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| what is the mode of action of phenols? |
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| denatures proteins and disrupts membranes |
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| what are the disinfectant applications of phenol? |
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| used on hard surfaces...but not widely used today because it has a strong odor. |
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| can phenols be used for antiseptic applications? |
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| they are rarely used because they are too toxic, but sometimes "carbolic acid" or Lister's old surgical antiseptic is used |
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| what is the mode of action of alcohol? |
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| denatures proteins, disrupts membranes (70-75% ethanol or isopropanol) |
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| what are the disinfectant uses of alcohols? |
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| disinfects lab benches or medical instruments |
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| When is alcohols used as an antiseptic? |
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| to externally wipe skin to reduce pathogen population before injections |
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| what form is chlorine used as a disinfectant/ antiseptic? |
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| Hypochlorite solutions...NaOCl |
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| what is the mode of action of chlorine? |
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| chemically oxidizes many types of cell components and biochemicals |
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| is chlorine ever used in as an antiseptic? |
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| no, too corrosive. |
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| what is an example of a quarterly ammonium compound? |
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| cetylpyridinium chloride |
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| what is the mode of action of quaternary ammonium compounds? |
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| ampipathic molecules interact with phospholipids in cell membranes, acts as detergents to disrupt lipid membranes |
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| what is the average wavelength of UV light in the electromagnetic spectrum? |
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| 100 to 400 nanometers |
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| what is the maximum absorption of UV light by DNA? |
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| 260 to 265nm |
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| what happens when DNA absorbs UV light? |
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| covalent linkages called pyrimidine dimers form between adjacent bases |
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| what is the most effective wavelength of UV light on germs? |
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| 260 to 265 |
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| What type of bacteria are more resistant to UV light than others? |
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| spores..Bacillus and Clostridium |
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| What do mutation repair systems do? |
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| repair damaged sections of DNA.....cleave the the covalent bond that created the thymine dimers and restore original linkage...never replace the thymines... |
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| selective toxicity of antibiotics |
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| these chemicals are usually much more toxic to microorganisms than they are to us or our cells. |
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| narrow spectrum antibiotics |
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| inhibits or kils a shorter list of bacterial species...ex. penicilin |
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| is penicillin more effective against gram positive or gram negative bacteria? |
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| gram positive |
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| broad spectrum antibiotics |
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| will act against most species of bacteria, inhibiting or killing gram positive and gram negative alike. |
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| Why do we say that "resistance is not an absolute quality?" |
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| if the dose of the drug is high enough, the bacterial cells can still be stopped |
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| What is the Kirby-Bauer Disk Diffusion Assay? |
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| assay that determines spectrum and response...antibiotic diffuses out of the disks and into the surrounding agar as an expanding circle of the drug. |
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| In the Kirby-Bauer Disk Diffusion Assay, what does a zone of inhibition look like? |
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| an area of no cell growth around the disk. |
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| In the Kirby-Bauer Disk Diffusion Assay, what does resistance look like? |
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| cell growth around the disk |
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| What are a few methods to determine cell count? |
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| 1) centrifugation 2) turbidity 3) direct microscopic counts 4) coulter count 5) Most Probable Numbers 6) quantitative plate counts |
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| spread plates count how many colonies in CFU/mL? |
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| 20-200 |
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| pour plates count how many colonies in CFU/mL? |
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| 30-300 |
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| What are some of the pathogens that could end up in milk? |
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| salmonella--> intestinal infections, listeria monocytogenes-->high mortality rate infections of blood...myobacterium tuberculous: agent of lung disease tuberculosis |
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| what is the difference between LTLT and HTST? |
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| low temperature, long time; high temperature, short time. |
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| What bacterium does Actvia contain? |
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| Bifidobacterium animalis |
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| what kind of oxygen tolerance do milk bacteria have? |
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| aerotolerant |
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| what two species of lactic acid bacteria are in yogurt? |
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| lactobacillus bulgaricus and streptococcus thermophilus |
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| What are the flavor molecules in yogurt? |
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| acetaldehyde and diactyl...organic molecules |
