Learning Module - Periods 3 and 4

BACTERIOPHAGE LIFE CYCLE

Bacteria must express the maltose receptor:

Under poor growth conditions, the lysogenic pathway is followed:

Under good growth conditions, the lytic pathway is favored:

Progeny phage are released from lysed bacteria:

PLAQUE GROWTH

Plaques enlarge by successive rounds of infection and lysis:

The extent of plaque formation depends on the Multiplicity of Infection (M.O.I.):

TRANSDUCTION

Conditions are chosen to promote lysogeny:

• Adsorb phage to DM700 at lower temperature (30° C)
• Grow bacteria on poor media (Minimal A glucose)
• Incubate plates at lower temperature (30° C)

Grow transductants under selective conditions, in our case we select for the ability to grow on media lacking cysteine

DATA TABULATION

Count the number of PFUs on a series of plates:

Calculate the number of PFU per mL of phage stock

For example: 37 plaques were observed.

Hence, (37 plaques / 0.1 ml) x 10^6 dilution = 3.7 x 10^8 PFU / mL of original phage stock.

Procede to LON-CAPA to answer the question for this Learning Module.