Microbiology Exam 2
stationary
Which phase of the growth curve are bacteria dying and dividing at the same rate?
Psychrophilic
Microbes that are cold living, below 0>21 degrees Celsius
False
True/false: During conjugation the donor loses his F+ plasmid as it is transferred through the pilus.
Be capable of growth at both cold and moderate temperatures
A facultative psychrophile will:
Obligate Aerobes
Aerobes that require oxygen/aerobic respiration
Alcohols denature proteins and disrupt microbial membranes
An advantage of using an alcohol as a disinfectant is that:
An endoenzyme
An enzyme that performs one of the steps of glycolysis is an example of:
You would determine which fermentation reactions occur in the water sample
Apply: After a sewer line bursts, you suspect your drinking water is contaminated by pathogens. Which of the following tests would be most effective in determining if E. coli bacteria (this species specifically) are present in a water sample?
Lipase is an exoenzyme that catalzyes a catabolic reaction
Apply: Bacteria that live on our skin often release lipase proteins that can break down our skin oils. The breakdown of skin oils enables these microbes to generate ATP. Characterize the role of the lipase protein using the metabolism terms you have learned.
1200
Apply: E. coli has a generation time of 20 minutes. After 40 minutes of exponential growth, how many bacteria will be present in a culture that contained 300 bacteria at time 0? hint: make a table showing the # of cells after each generation.
Boiling causes microbial enzymes to denature
Apply: Imagine that the city issues a water advisory and asks all residents to boil their water. How does boiling ensure your water is safe to drink?
Antiseptic
Apply: The chemical betadine, which contains iodine, is commonly applied to a patient's skin before an incision is performed. Betadine is therefore an example of a:
The drug will prevent the enzyme's substrate from entering the enzyme's active site
Apply: Your prescribe a patient with high cholesterol a drug called a statin, which is a competitive inhibitor of an enzyme needed for cholesterol synthesis. How will this drug affect its target?
Bacillus Cereus Endospores
Bacteria that grows and germinate in improperly refrigerated rice
selective medium and a differential medium
EMB agar is a medium used in the identification and isolation of pathogenic bacteria. EMB contains a dye that inhibits the growth of gram-positive bacteria and a dye that distinguishes between lactose fermenting and non-lactose fermenting organisms. Lactose fermenters form metallic green colonies, whereas the non-fermenters form completely colorless colonies. Based on this info, EMB agar is an example of which of the following?
Yes, offspring receive identical copies of chromosomes but mutations?(permeant DNA change) can happen if DNA polymerase makes a mistake or if DNA is damaged
DO offspring receive identical copies of chromosomes ?
oxidize macromolecules-inhibit functions iodine- antiseptic/water purification
How do Halogens control growth?
true
True or false In translation, the mRNA codons match to tRNA anticodons, allowing the correct amino acid to be added to the peptide
determine the concentration of microbes in a liquid sample
In the lab, you prepare a pour plate in order to:
Mesophilic
Microbes that grow at human body temp 18-24 degrees Celsius
thermophilic
Microbes that grow in heat, 40-90 degrees Celsius
False
Naturally-formed biofilms usually consist of genetically identical bacterial cells that grow in a visible mass on the surface of an object.
Allow a cell to regenerate NAD+
One similiarity between lactic acid fermentation and ethanol fermentation is that BOTH reactions:
-Ribosome assembles at a start codon on the mRNA strand -tRNA brings in matching amino acid for start codon. -Ribosome catalyzes formation of peptide as it moves down the mRNA strand -Ribosome releases peptide and disassembles at the stop codon
Place the following in the correct order of translation:
Remove 1 mL from the starting culture, add to 9 mL of broth making 1:10 Mix culture and remove 1 mL mixture and add to 9 mL broth (1:100) Mix culture and remove 1 mL mixture and add to 9 mL broth (1:1000) Mix culture and remove 1 mL mixture and add to 9 mL broth (1:10,000)
Place the serial dilution in correct order
-RNA Polymerase binds the DNA at a promotor, transcribes complementary mRNA -mRNA transcript is bound by small & large ribosome units at the start codon -The tRNA anticodon binds with mRNA codon, bringing in correct amino acids -ribosome translation proceeds until a stop codon and disassembles
Put the following in order to create a peptide
-RNA Polymerase binds to a Promotor DNA Sequence -RNA polymerase runs down DNA linking RNA nucleotides to form RNA Transcript -RNA Polymerase stops when it reaches a termination sequence -mRNA is released from RNA polymerase and the DNA
Put the steps of transcription in order:
Facultative anaerobe
Recall: If a microbe performs aerobic respiration when oxygen is present, but will use another pathway (fermentation) if oxygen is not, what would you classify this organism as?
pasteurization
Recall: Which of the following methods does NOT achieve sterilization, but instead just reduces the quantity of microbes?
Psychrophiles
Recall: Which of the following microbes can actively grow on food stored in the fridge and cause food spoilage?
-bacteriophages can carry DNA from the previous host bacteria to the new one -bacteriophages steal host machinery to make copies of itself -recombination introduces former host bacterial DNA into new host chromosome
Select all of the following that are correct regarding Transduction:
-Allows for very little genetic diversity -Gene transfer happens in the same generation -creation of two daughter cells
Select all of the following that corresponds with Vertical Gene Transfer
-environmental DNA is taken into cell -cells capable of transformation are "competent" -extracellular DNA can recombinate once taken up by transformation
Select all of the following that is correct about Transformation
A CFU is pure colony derived from a single microbe You can use a CFU to perform a gram stain During a serial dilution we count CFUs to get a concentration
Select all true statements regarding a colony (aka colony forming unit):
-pour plates can allow growth of anaerobic bacteria, spread plates don't -pour plates and spread plates are used to find concentrations of bacteria
Select the correct answers regarding pour plates and spread plates
NAD+
The fermentation of pyruvate into carbon dioxide and ethanol directly generates: (select ALL that are correct) ATP
False
True of false? Biofilms are made up of one species of bacteria, a culture is made up of many diverse bacteria
true
True of false? Reverse transcription makes a DNA copy of an RNA virus and can get integrated into the host chromosome
Thermophile
Think back to Unit 1 and Louis Pasteur's development of pasteurization, which of the following types of microbes do you think would survive?
true
True or false DNA replication in prokaryotes proceeds in both directions from the origin sequence 20s
Adding phenol to your water before drinking it
Understand: If you needed to purify water to drink, you could safely use all of the following methods at your house EXCEPT for:
It receives and then transfers electrons between molecules
Understand: What is NAD+ used for in microbial metabolism?
Aerobes make enzymes that inactivate the reactive oxygen molecules produced by metabolic reactions
Understand: Why isn't oxygen toxic to obligate aerobes?
Heating, High/low pH. and competitive/non-compettive inhibitors.
What are some of the ways that enzymes can be inhibited/denatured?
phenols Halogens heavy metals Alcohol Soaps/detergents
What are the 5 chemical agents to control growth?
Heat, cold, drying, ionizing radiation and UV light
What are the 5 physical methods to control Growth?
Temperature, pH , salt, oxygen requirements
What are the four factors that affect microbial growth?
1) parents strands separate 2) nucleotides bind to complementary bases on the parent strand 3) DNA polymerase catalyzes formation of covalent bonds between nucleotides
What are the steps of DNA replication?
1) RNA polymerase binds to the promoter sequence 2) DNA Strands get separated and RNA polymerase moves down DNA 3) complementary RNA nucleotides are linked to form an RNA transcript 4) Transcription will stop when RNA polymerase reaches termination sequence
What are the steps of Transcription?
mRNA(messengers) rRNA+ tRNA
What are the two RNA molecules produced by translation ?
endoenzymes and exoenzymes
What are the two categories of enzymes?
Selective media and differential media
What are the two types of Diagnostic media?
Sterilization and disinfection
What are the two ways of controlling microbial growth?
A large zone of inhibition around the disk.
What do you expect to observe in a filter-paper disk diffusion assay if you are using a chemical that is highly effective in killing/inhibiting the growth of microbes?
Flexible and able to tolerate a specified condition
What does facultative mean?
Only able to grow at only the specified condition
What does obligate mean?
Susceptibility of bacteria to the antimicrobial drug
What does the 'zone of inhibition' tell us?
exoenzymes
What enzymes are exported enzymes? Ex: the enzyme that breakdown penicillin
mRNA read codon sequences
What happens in Translation?
kills bacteria
What is a bactericidal?
inhibit growth
What is a bacteriostatic?
3 nucleotides that code for a specific amino acid
What is a codon?
mannitol salt agar because t has a high salt content and can only grow halophilic bacteria
What is an example of selective media?
Reducing the # of microbes but not necessarily killing them off.
What is disinfection?
Electron transport chain
What is it called when electrons are passed from reduced electron carriers , down a chain of membrane bound proteins(?channels)
Carries info from DNA to ribosomes for translation into proteins
What is mRNA's role in translation?
Remain RNA. They don't get transled, don't encode proteins and they are still used in translation
What is rRNA and tRNA's role in translation?
Killing/removing ALL microbes, most extreme form of controlling microbes and not always possible
What is sterilization?
Disinfectant: Applied to non-living surface Antiseptic: Applied to living tissue (Alcohol swabs)
What is the difference between a disinfectant and an antiseptic?
glycolysis
What is the first step for all metabolic reactions that we discussed in class?
the making of RNA copy of a segment of DNA DNA: Stable, long term instruction book mRNA: Less stable, is a temporary copy of the instructions that can be used to build proteins
What is transcription?
recombination
When new DNA integrates into the host chromosome this is called:
Endoenzymes
Which enzyme acts within the cell that made them
Non-competitive inhibitor
Which enzyme does not bind in the same spot as the substrate and changes chap of enzyme while inhibiting substrate reaction
Competitive inhibitor
Which enzyme inhibitors compete with substrate for active/binding site
-Transduction -Conjugation -Transformation
Which of the following are methods of Horizontal gene transfer:
A small amount of ATP Pyruvate Reduced electron carriers
Which of the following are products of glycolysis? (select ALL) Correct!
Allosteric inhibitors (non-competitive inhibtitors), heat
Which of the following change the shape fio the enzyme inorder to regulate/.inhibit functino?
Ionizing radiation UV light causing thymine dimers
Which of the following could cause Induced mutations (select all correct):
Krebs cycle: plasma membrane
Which of the following metabolic pathways is matched incorrectly to its location in a prokaryotic cell?
promotor, gene, RNA polymerase, mRNA, termination sequence
Which set of terms apply only to transcription:
To dilute microbial samples to do a plate count
Why do we perform serial dilutions?
Oxygen leads to formation of highly reactive molecule and free radicals
Why does oxygen kill some bacteria?
it denatures proteins & dissolving membranes, evaporates quickly, does not work on endospore's/some viruses. Friction required to penetrate biofilm
Why is Alcohol a way to control growth.?
It damages DNA, doesn't penetrate most material, endospores can survive
Why is UV light a physical method to control growth?
-metabolic reactions slow way down or stop -liquid water isn't dualizable -cytoplasm crystalizes
Why is cold a physical method to control growth?
Inhibits growth by removing water
Why is drying a physical method to control growth?
x-rays, gamma electron beam
Why is ionizing radiation a physical method to control growth?
1:10 dilution
You perform a dilution by adding 10 mL of a bacterial culture to 90 mL of medium. After mixing this solution, you create a second dilution by adding 10 mL of your first dilution to 90 mL of new medium. What is the total dilution of this second dilution compared to the original culture?
-DNA rep. forms two new chromosomes each with a parent and daughter strand -DNA is antiparallel -RNA Polymerase binds to DNA at the promotor to begin transcription
elect all of the following that is true regarding DNA:
pyruvate
first molecule that starts anaerobic respiration, aerobic respiration and fermentation reaction
-Doesn't kill microbes -physical removal of microbes, scrubbing essential detergent disrupts membrane's
how are soaps/detergents used to control growth
Disrupts membrane and denatures proteins, persists on surface for longer time periods. Both disinfectants and antiseptic
how do phenols control growth?
Through binary division
how do prokaryotic cells divide?
Selective Media
media that encourages growth of certain types of organisms and/or suppresses growth of others (antibiotic). May contain dyes that inhibit growth.
Differential media
media that results in observable changes in response to biochemical reactions; has a color change due to pH indicators
Obligate Anaerobes
microbes that cannot live in presence of oxygen
Hyperthermophile
microbes that grow in extreme heat 70-105 degrees Celsius
Gene expression
production of RNA molecules and portions by a cell is called?
True
true/fasle? The difference between F+ bacteria and Hfr bacteria, is that F+ is on a plasmid and Hfr pilus gene is in chromosome
Cold= Slowed metabolic reaction Heat=denaturation
what are the two factors that influence enzyme activity?
Competitive and noncompetitive
what are the two types of enzyme inhibitors?
Water under pressure to reach high enough temperature to sterilize and kill everything
what is autoclaving? Is it sterilization of disinfection?
Kills most microbes but not hot enough to kill everything. (ex: water 100 degrees Celsius) disinfection
what is boiling? Is it sterilization of disinfection?
Bunsen burner, incineration, etc. Sterilization
what is dry heat? Is it sterilization of disinfection?
Microbial Growth
what is it called when the number of ells in a population is increase?
when working with liquid can be both
what is moist heat? Is it sterilization of disinfection?
milder form of heat treatment (disinfectant) modern: Ultra high hear for 1 second Old: 63 degrees Celsius for 30 mins
what is pasteurization? Is it sterilization of disinfection?
Alchol
what is the most common chemical way to control growth?
1:100 X 1:100= 1: 10,000 final dilution
what would be the final dilution of two 1: 100 dilution
Inhibit enzymes silver, mercury, copper
why are heavy metals a way to chemically control growth? what are some examples?
Structure determines the function of the enzymes
why must enzymes maintain 3D structure?
