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TRANSDUCTION TUTORIAL

MICROBIAL GENETICSMCBG2027

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When a generalized transducingparticle infects a bacterial cell

1. It transfers viral DNA to the recipientbacterium

2. The bacterial DNA integrates into the

recipients genome forming a partial diploidcell

3. The recipient cell is killed by lysis

4. The bacterial DNA can integrate into therecipients genome and change thegenotype of the cell

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In specialized transduction 1. Only a few specific genes from the

bacteriophage are transferred to therecipient by the phage

2. Only genes on a plasmid can be

transduced 3. Only phage genes near the bacterial

attachment site can be transduced

4. Only bacterial genes near the site ofintegration of the phage DNA can betransduced

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A defective lambda phage can 1. Integrate into a recipient cell only if a

helper phage is present in the same cell 2. Integrate into a recipient cell if the

helper phage is present in the same

population 3. Reproduce in the recipient cell without

the aid of a helper phage

4. Yield a stable transductant if a singlecrossover event occurs with therecipient cells genome

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VIRUS ASSAYS

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PLAQUE ASSAYS Plate put several dilutions

Each plaque arises from reproduction of

a single virion

Count plaque forming units (PFUs)

Different viruses different plaquemorphologies

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How many types of phages canyou identify from the plate below

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ENDPOINT ASSAYS Amount of virus required to cause

disease or death Cell cultures cultivated with serial

dilution of virus

LD50 (lethal dose) endpoint dilution atwhich 50% of host cells are killed

ID50 (infectious dose) dose at which50% of hosts are infected under thespecific conditions

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DOSE-RESPONSE CURVE

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The dose response curve belowwas obtained for M13 phage thatinfects Escherichia coli

1. What is the LD50

for the M13 strain?(Estimate theclosest value)

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2. If 37 PFUs were countedat the LD50 what was theconcentration of the original

viral suspension if 100 lwas plated out?

3. If the LD50 for M13 is 10-8

and the concentration ofphage particles at thisdilution is 230 PFUs/0.1ml.

What is the concentration ofthe undiluted phage usedper ml?

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Compare transduction and

lysogenic conversion

Transduction Lysogenic conversion

Carried out by viruses

Transfer of bacterialgenes

Imparts newcharacteristic

Genetic

recombination

Carried out by viruses

Integration of viralDNA with bacterial

DNA

Imparts newcharacteristic

No geneticrecombination