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Micro202 exam 2
microbiology
82
Microbiology
Undergraduate 2
10/25/2015

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