MI 1.2 Quiz
Mode of Action Description (including where/how it attacks the bacterial cell) -Pencillins
Interferes with interpeptide linking of the peptidoglycan
What does a microbiologist do?
Investigates the growth, structure, development, and other characteristics of microorganisms like bacteria.
Why did neither strain grow on the plate containing both streptomycin and ampicillin?
It did not grow because they are susceptible to the antibiotics.
Why is the clear area surrounding an antibiotic disk called the zone of inhibition?
It is called the zone of inhibition because that is the area where the bacteria can not grow.
Why is it important to understand the structure of a bacterial cell when developing an antibiotic?
It is important so that you know whether the antibiotic will be effective or not. If you know how the bacteria is structured you may figure out a way for the antibiotic to be able to penetrate through its layers.
Why is it important to use aseptic technique when working with bacteria in the lab?
It is important to use the aseptic technique so that we can keep a sterile environment and not containment the bacteria. It helps make sure nobody gets infected by the bacteria.
What is one of Angela's biggest challenges as a microbiologist?
Keeping up with changes to antibiotics, since bacteria can become resistant to the antibiotic then a new one needs to be made.
Which plate or plates can NEITHER E. coli I nor E. coli II grow on?
LB + Strep + Amp
Which plate or plates can BOTH normal E. coli I and E. coli II grow on?
LB Agar
Which plate or plates can normal E. coli II grow on?
LB Agar and LB + Amp
Which plate or plates can normal E. coli I grow on?
LB Agar and LB + Strep
Examples of these antibiotics-Fluoroquinolones
Levofloxacin (Levaquin) Ciprofloxacin (Cipro) Moxifloxacin (Avelox) Olfoxacin Gemifloxacin (factive) Delafloxacin (Baxdela)
Give a brief summary of how the test is performed.
Make a lawn by spreading the bacteria evenly on the plate, place antibiotics disks on the lawn, grown the bacteria, measure the diameter of the zone of inhibition, then refer to the reference table to determine if the antibiotic is resistant, intermediate, or susceptible.
ribosomes
Makes proteins -Protein synthesis takes place in the bacterial ribosome. mRNA is read/amino acids are assembled.
How is the zone of inhibition measured?
Measure the diameter of the clearing to see how susceptible the bacteria is/ using a maker and measuring in millimeters
Explain how Angela created a mix plate.
Using the aseptic technique Angela moved one colony of each of the E.coli strains to the mix plate. She used and E.coli I strain from the LB Agar + Streptomycin plate and an E.coli II strain from the LB Agar + Ampicillin plate.
Efflux
Bacteria that often becomes resistant to antibiotics. Efflux pump exports antibiotics and other compounds out of the cell. Then the antibiotic enters through a channel called the porin then is pumped back out the bacteria by the efflux pump.
Transduction (further explained)
Bacterial DNA is transferred from one bacteria to another inside a virus that infects bacteria. The viruses are called bacteriophages/phage. The phage takes over the bacteria's genetic processes to produce more phage. During the process bacterial DNA may be incorporated into the new phage DNA, when the bacteria die the phages will go on to infect other bacteria.
Mode of Action Description (including where/how it attacks the bacterial cell)- Sulfa antibiotics
Binds and inhibits an enzyme called dihydropteroate synthase--critical for synthesis of folate-- essential nutrient
Effective against Gram +, Gram - or both (Sulfa antibiotics)
Both--considered a wide spectrum antibiotic
Effective against Gram +, Gram - or both (Fluoroquinolones)
Both--have excellent in vitro activity against a wide range of gram-negative and gram-positive bacteria
Effective against Gram +, Gram - or both (Tetracyclines)
Both--their use is decreasing to increasing instance of bacterial resistance but is useful in treating acne, the urinary tract, respiratory infections, and chlamydia infections.
What is one of Angela's greatest rewards?
Finding the causes of infections and finding treatments that work for the patients.
Transformation (further explained)
Genes are transferred from one bacteria to another as ¨naked¨ DNA. When the cell dies DNA can be released and other bacteria in close proximity can get a hold of the free floating DNA and incorporate it in their own DNA. The DNA might have advantageous genes/antibiotic resistance genes which will benefit the cell.
Destruction or Inactivation
Genes that produce enzymes that degrade/deactivate the antibiotic, making it ineffective against the bacteria.
Connected to UTIs, pneumonia & meningitis
Gram Negative
E. coli Klebsiella Acinetobacter Pseudomonas Aeruginosa
Gram Negative
Endotoxins are responsible for making the cell wall of the gram-negative and are produced by gram negative bacteria
Gram Negative
Is (Neisseria meningitidis) Gram + or Gram -?
Gram Negative
Outer layer (membrane) protects them & can be used to keep antibiotics from entering, making them generally harder to fight with antibiotics
Gram Negative
What has a final color of pink/red because CRYSTAL VIOLET is not retained & SAFRANIN stain is red (color box red).
Gram Negative
Which has Thinner layer of peptidoglycan, has an outer membrane- lipopolysaccharide and protein?
Gram Negative
Which one HAS an outer membrane?
Gram Negative
Exotoxins--can be inactivated (killed) by high temps & are capable of being bound by antibodies from the immune system
Gram Positive
Gram positive bacteria are starting to be resistant to antibiotics.
Gram Positive
Staphylococcus (i.e. staph infection) Streptococcus (i.e. strep throat) Clostridia such as C. Difficile Bacillus anthracis (i.e. anthrax) Listeria monocytogenes (i.e. listeria)
Gram Positive
The thick cell wall of the gram positive bacteria gives greater access to antibiotics and this allows them to penetrate the cell as well as interact with the peptidoglycan more easily.
Gram Positive
What has a final color of purple after being stained with crystal violet?
Gram Positive
Which as a THICKER layer of peptidoglycan protein? Gram Negative or Gram Positive?
Gram Positive
Which one has NO outer membrane?
Gram Positive
What structure or structures contained the transferred gene?
Plasmid
What are the two structures that carry genes in bacteria?
Plasmids and Bacterial chromosomes
Mode of Action Description (including where/how it attacks the bacterial cell)-Tetracyclines
Prevents growth/reproduction by preventing translation of proteins needed by binding to parts of the ribosome
outer membrane (capsule)
Protects the bacterial cell/serves as a barrier against phagocytosis by white blood cells
cell wall (cell envelope)
Provides support, structure, and protection for the cell. Is made up of cellulose and layers that are the middle lamella, primary cell wall, and secondary cell wall
zone of inhibition
Region around a chemical saturated disc, where bacteria are unable to grow due to adverse effects of the compound in the disc.
Antibiotic Resistance
Resistance to one or more antibiotics, usually due to additional genetic information
Describe Angela's path to becoming a microbiologist.
She started at the University of North Florida and got her bachelor's degree in Biology, then she became a high school biology and chemistry teacher. While teaching, she went to Florida State College of Jacksonville and got her associates degree in medical technology. Finally, she is now a Microbiologist at Mayo Clinic in Jacksonville, Florida.
plasmids
Small circular DNA fragment found in the cytoplasm that contain code responsible for antibiotics resistance and other characteristics/ can be transferred between bacteria.
Sue Smith wants to know why she has to continue taking her antibiotics even though she is feeling better. Explain the importance of Sue completing her gull course of antibiotics as prescribed.
Sue needs to continue to take her antibiotic because even though she is feeling better, the bacteria in her body might not have fully died and if she takes all of it is will help the bacteria not to come back and infect her again.
Examples of these antibiotics-Sulfa antibiotics
Sulfamethoxazole-trimethoprim (Bactrim, Septra) Erythromycin-sulfisoxazole (Eryzole, Pediazole) Glyburide (Diabeta, Glynase Pres Tabs)
Nucleoid
The DNA-containing area of a bacterial cell
Why did the E. coli I strain grow on both the LB agar plate and the plate with streptomycin, but not on the plate with ampicillin?
The E. coli I strain grew on the LB agar plate because there is no antibiotic on it that could stop it from growing. The plate with streptomycin also grew because it is resistant to the antibiotic. However, it did not grow on the plate with ampicillin because it is susceptible to the antibiotic.
Based on the results of the experiment, as well as what you learned about the mechanisms of gene transfer between bacterial cells, was the streptomycin resistant gene transferred from Strain I to Strain II, or was the ampicillin resistant gene transferred from Strain II to Strain I? How do you know?
The ampicillin resistant gene was transferred from Strain II to Strain I. We know this because in Experiment I Strain II was resistant to the ampicillin but Strain I was susceptible. Then when the mixed plate was created in Experiment III we saw that the new bacteria created from Strain II, and I was also resistant to ampicillin.
What would you expect to happen around the control disc in a Kastle-Bauer test?
You would expect to see that the antibiotic is most concentrated near the center of the disk
Propose reasons why an antibiotic may not be as effective at inhibiting E. coli as it is against B. cereus
-E. coli is gram negative and B. cereus is gram positive -different structures (cell wall especially-gram positive has more peptidoglycan, thicker wall) -different forms of antibiotics target different structures
Mutation
A change in DNA that can cause a change in the gene product/target of the antibiotic.
How would a genetic mutation in the bacteria's DNA cause the cell to become resistant to a particular antibiotic?
A genetic mutation is caused when one gene transfers to another, so if (x) bacteria gets one gene from another bacteria (y) that calls for resistance than (x) bacteria could also become resistant as well because of the DNA transferring
cytoplasm
A jellylike fluid inside the cell in which the organelles are suspended (excludes nucleus) -Bounded on the outside by the cell envelope/cytoplasm is mostly water/ in it are bacterial inclusions/ nucleoid /plasmids/ribosomes & storage granules / components necessary for bacterial metabolism.
plasma membrane
A membrane found in all cells that protects the interior of the cell wall. Transports nutrients into the cell and transports toxic substances out of the cell/contains lipids
Which strain of E. coli must have been growing on the LB +Strep +Amp plate?
A new form of E.coli I
nucleoid
A region in the bacteria visible in transmission electron micrographs. Most of the bacterial DNA is found here along with RNA & proteins/ not bounded by membrane.
Plasmid
A small ring of DNA that carries accessory genes separate from those of the bacterial chromosome
Antibiotic
A substance produced by or derived from a microorganism and able in dilute solution to inhibit or kill another microorganism
Endotoxins
A toxic component of the outer membrane of certain gram-negative bacteria that is released only when the bacteria die. -Is found in gram-negative bacteria and is found on the outer membrane of the cell wall. Are responsible for the organization and stability of the cell wall.
Examples of these antibiotics-Tetracyclines
Adoxa TT (doxycycline) Oralxyl (doxycycline) Terramycin (oxytetracycline)
Why are antibiotics NOT effective against viruses? (Think back to what you learned about viruses in PBS.)
Antibiotics are not effective against viruses because viruses use their host cell to carry out their activities. Antibiotics are meant for seeking out bacterial cells and killing them, while viruses use the host cell to replicate and survive.
Patients forgetting to take their antibiotics are not the sole cause for antibiotic resistance. Explain at least two other possible causes of the development of antibiotic resistance.
Antibiotics might also become resistant because of over-prescription of the antibiotic and also because of new antibiotics being discovered.
How do antibiotics work without harming the surrounding human cells?
Antibiotics target the cell wall of the bacteria and human cells do not have cell walls, so they will not be able to harm human cells.
Which type of gene transfer most likely occurred?
Conjugation
Effective against Gram +, Gram - or both (Pencillins)
Gram-positive because Gram-negative bacteria has a lipopolysaccharide and protein layer that surrounds the peptidoglycan layer of the cell wall, so it prevents the penicillin from attacking
Where is the gene found for disease resistance?
E. coli I -Chromosomal DNA/Nucleoid E. coli II -Plasmid
Which antibiotic is the strain resistant to?
E. coli I -Streptomycin E. coli II -Ampicillin
What bacteria was discussed in Angela's Memorable Case and what severe condition did it cause?
E. coli and it caused the patient to get diarrhea and sepsis.
What did Angela streak on the side of the plate labeled I?
E.coli I strain
What did Angela streak on the side of the plate labeled II?
E.coli II strain
Which of the following best explains what happened?
E.coli II transferred its ampilicin resistance to E.coli I
Why are penicillins often more effective against Gram-positive bacteria than Gram-negative bacteria?
Gram-positive is easier to penetrate because it only has one layer of membrane whereas the gram-negative bacteria has the plasma membrane as well as the outer membrane.
pili/pilus
Hollow, hairlike structures made of protein, allow bacteria to attach to other cells. A specialized pilus, the sex pilus, allows the transfer of plasmid DNA from one bacteria cell to another.
Which antibiotic would be the most effective treatment for an infection with the E. coli?
I believe that Chloramphenicol will be the most effective treatment for E.coli because of its diameter and because its zone of inhibition is large.
What mechanism of gene transfer do you think was responsible for transferring the antibiotic resistant gene between these two strains of bacteria? Explain your answer.
I think the mechanism of gene transfer that was responsible for transferring the antibiotic resistant gene between the two strains of bacteria was the conjunction mechanism. This is because when Strain II transferred to Strain I bacteria that was once susceptible (Strain I) became resistant and also was transferred through plasmids. We know it is not Transformation because we do not have any additional bacteria, and we know it's not Transduction because there is no virus involved.
What class of antibiotics would you prescribe for Sue? Explain your answer.
I would use the sulfa antibiotics because the bacteria she is infected with is gram-negative so penicillin wouldn't really work for her. Sulfa antibiotics destroy bacteria by coming in contact with the folic acid synthesis of bacteria.
Describe the zone of inhibition for a resistant bacteria.
If the bacteria is resistant than the zone of inhibition would not have as much bacteria around the disk like/ little dots of bacteria.
Describe the zone of inhibition for a susceptible bacteria.
If the bacteria is susceptible there will more bacteria around the disk/ more dots.
Given what you know about antibiotics, what other variable besides missing doses, might affect the effectiveness of an antibiotic?
If you take antibiotics that are expired they obviously would not be as effective and also if you take too much of the antibiotic it will not be effective.
What are some characteristics necessary for success?
Independent decisions, communication, getting results
Mode of Action Description (including where/how it attacks the bacterial cell)- Fluoroquinolones
Inhibits two enzymes that are involved in bacterial DNA synthesis--DNA topoisomerases--which are essential for bacterial DNA replication
Conjugation (further explained)
Mediated by plasmids (replicates independently of the chromosome). When the two cells get into close proximity it forms the pilus, then the plasmid duplicates its self and is transferred from one bacteria to another. This enables a suspectible bacteria to acquire resistance to an antibiotic agent
flagellum/flagella
Motility/ long appendages which rotate by means of motor in the cell envelope.
Recall the name of the pathogen infecting Sue.
Neisseria meningitidis
What is Angela's career advice?
Not to work in laboratories since the job requires flexibility in hours and days unless you don't want to work the regular 9 to 5 The job is good for people who don want to go into nursing but still enjoy science and helping people.
Classify each of the tested antibiotics as limited or broad spectrum antibiotics
Pencillin-narrow Ampicliin-broad Streptomycin-broad Tetracycline-broad Chloramphenicol-broad Gentamicin-broad
Examples of these antibiotics-Penicillins (β-Lactam antibiotics)
Penicillin Amoxycillin Ampicillin
How would a bacterial cell "share" this mutation with other bacterial cells?
The bacteria would have to reproduce if it wanted to share the mutation with other bacterial cells and would create a new type of bacteria.
What cellular components do some bacterial cells have that make them powerful pathogens? Explain your answer.
The cellular components are the pili and the capsule/outer membrane. Pili allows bacteria to attach to other cells and the capsule protects the bacteria cell and cells from being destroyed.
Conjugation
The one-way transfer of DNA between bacteria in cellular contact
By what process were the bacteria streaked onto the plate?
The process is called the isolation streak.
What was the purpose of culturing bacteria on these four plates?
The purpose was to see individual colonies of the bacteria, so we can analyze it.
Craft an explanation for Angela about what the results indicate about the new strain of bacteria produced.
The results are showing that there was positive growth on all 3 agar plates so by mixing the E.coli I strain and the E.coli II strain that means they are now fully resistant to both streptomycin and ampicillin.
When you remembered to take your antibiotic why did this simulation have you remove the Least Resistant Bacteria first?
The simulation had us remove the Least Resistant first because that bacteria had a larger amount than the rest of the bacteria in the body.
Transduction
The transfer of genetic material from one organism (such as a bacterium) to another by a genetic vector
Transformation
The uptake and expression of foreign DNA by a cell
Describe the growth on the mix plate after incubation.
There is a lot of growth from the bacteria on the plate.
What is the purpose of a Kastle-Bauer test?
To find out if a particular kind of antibiotic stops bacteria from growing.
Explain the purpose of creating a mix plate
To make a new strain of bacteria, allows DNA to transfer between the two strains.
