Attack of the Superbugs 1 lesson 1.2.2 PDF

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CONCLUSION 1. What was the purpose of culturing bacteria on these four plates? -2 plates with 1 type of antibody each: find which strains of bacteria are immune to one type of antibody. 2 other plates: controls to ensure the bacteria would grow in normal conditions 2. How did your predicted results compare to your observed results? -My predicted results were correct. i thought that only one strain of bacteria would grow on the plate with one antibody, none would grow on the plate with both, and both grew on the plate with none 3. Why did the E. coli I strain grow on both the LB agar plate and the LB agar plate with streptomycin but not grow on the LB agar plate with ampicillin? -The E. coli I strain was resistant to streptomycin. It can grow on plates with no antibiotics or streptomycin. it is not resistant to ampicillin, so the ampicillin killed it so it couldn't grow 4. Why did neither strain grow on the plate containing both streptomycin and ampicillin? -Both bacteria were immune to one form of antibiotic. antibiotics still usually work on other strains, just not as effectively. e. coli I's growth was prevented by ampicillin, while e. coli II's growth was prevented by streptomycin 5. Explain what the results indicate about the new strain of bacteria produced when both strains of E. coli were mixed together. -The new strain inherited the other resistance in addition to its original resistance. The new strain resists both ampicillin and streptomycin

6. Based on the results of the experiment as well as what you learned about the mechanism 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?

-Ampicillin resistance was transferred from strain II to strain I. Ampicillin resistance is found in the plasmids, which are easier to move and replicate. Streptomycin resistance is found in the chromosomal dna, which is harder to access 7. 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. Conjugation- Conjugation in bacteria is comparable to copulation in mammals. In this case, two bacteria connect to each other using something called a Pilus. When the connection is done, DNA can be transferred from one cell to the other (A to B and/or B to A). The bacterium which eventually gives the DNA is referred to as the donor cell. Donation of DNA is made possible by a phenomenon called the F factor. F here stands for fertility. Transduction- During transduction, the transfer of the antibiotic-resistant gene between two strains is purely accidental.

Results for Mixed Culture Agar Plates

Bacterial Growth

LB agar + streptomycin

Grew(+)

LB agar + ampicillin

Grew(+)

LB agar + streptomycin + ampicillin

Grew(+)

Agar Plates

E. coli I Strain Observed Results

E. coli II Strain Observed Results

LB agar

Growth (+)

Growth (+)

LB agar + streptomycin

Growth (+)

NO Growth (-)

LB agar + ampicillin

NO Growth (-)

Growth (+)

LB agar + streptomycin + ampicillin

NO Growth (-)

NO Growth (-)

24 hours later Agar Plates

E. coli I Strain Observed Results

E. coli II Strain Observed Results

LB agar

Growth (+)

NO Growth (+)

LB agar + streptomycin

Growth (+)

NO Growth (-)

LB agar + ampicillin

NO Growth (-)

Growth, just a little (+)

LB agar + streptomycin + ampicillin

NO Growth (-)

NO Growth (-)

○ Mutation ○ Target protein ○ Genes ○ Antibiotic ○ Conjugation ○ Resistant gene ○ Plasmid ○ Pilus ○ Transformation ○ “Naked” DNA ○ Transduction ○ Bacteriophage There are four main methods of antibiotic resistance that can take place within and between bacteria. They are mutation, destruction/inactivation, efflux and gene transfer. A mutation can occur almost suddenly and take place in the DNA that then changes the bacteria structure making the antibiotic ineffective against it. The mutation leads to a change in the gene that is now a resistant gene against a certain antibiotic. While in destruction/inactivation, the cell has little soldiers(enzymes) that

make the antibiotic ineffective before it can reach the target protein in the cell. On the other hand, efflux is the pumping out of antibiotics before it reaches a lethal saturation in the cell. Then in gene transfer which can be further categorized as conjugation, transformation and transduction also has something to do with genetic code. Where a conjugation is the movement of plasmid from one bacterium to another through a pilus that forms between the two bacteria. The plasmid includes an antibiotic resistant gene, which then copies and goes into the other bacteria giving it that gene. Then transformation is the incorporation of “Naked” DNA released in the environment from the leftovers of other dead bacteria. Finally, transduction which uses bacteriophage that injects another bacterium taking it over and incorporating it DNA that may have included resistant genes against antibiotics...