1. How does Ampicillin prevent bacteria from growing? 2. The Amp gene encodes a

Question

1. How does Ampicillin prevent bacteria from growing? 2. The Amp gene encodes a protein called beta-lactamase. Why is this gene expressed in our plasmid? 3. How does beta-lactamase work? 4. Other experiments use different antibiotics as selectable markers, including Spectinomycin and Gentamycin. Pick one of these and describe how this antibiotic affects bacteria. 5. Antibiotic-resistant bacteria are previously sensitive to an antibiotic become antibiotic resistant? a growing public-health threat ow do bacteria that were 21

Explanation / Answer

1. Ampicillin( broad spectrum and acid resistance) is semisynthetic penicillin.It acts as a cell wall inhibitor. It inhibits transpeptidase enzyme used in the synthesis of the cell wall by bacteria.

2. AmpR gene is present in the plasmid to provide the organism resistance to the particular antibiotic. Cells having AmpR gene are termed as + AmpR and can survive and form colonies on LB agar that has been provided with ampicillin.

3) B-lactamase breaks the bond in the B-Lactum ring of the antibiotic ( say ampicillin or penicillin ) to disable the molecule. Bacteria having this enzyme can survive the antibiotics having B-Lactum rings.

4) I'm choosing Gentamycin to show how it affects bacteria. Gentamycin is an aminoglycoside group of antibiotic. It binds to the 30s subunit of the ribosome and thus leads to the formation of abnormal proteins and it also leads to the damage of bacterial cell membrane thus killing bacteria.This is how it works.

5) There are many ways by which a bacteria can become resistant to antibiotic :

a.Mutation in bacterial DNA: Any mutation in the target protein can prevent the antibiotic from binding to the particular site. Antibiotic will not be able to recognise that site and thus can not kill the bacteria. Hence, bacteria become resistant to that antibiotic.

b.Transfer of antibiotic resistant gene from one bacteria to another bacteria: Via horizontal gene transfer.

c.Changes in bacterial permeability.

d. Alteration in metabolic pathways.

e. Alteration of cellular physiology.

f. Extrachromosomal resistance.

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