Multiplicity of infection

Multiplicity of infection

1. CalculationofMultiplicityof
Infection(moi)
Dr. S. SivasankaraNarayani.,M.Sc.,M.Phil.,Ph.D.,MRSB(UK)

2. Multiplicity of infection (moi)
Anexperimentwithbacteriophagetypicallybeginswithaninitialperiod
duringwhichthevirusisallowedtoadsorbtothehostcells.
Itisimportanttoknowtheratioofthenumberofbacteriophagestothe
numberofcellsatthisstageoftheinfectionprocess.
Toomanybacteriophagesattachingtoanindividualcellcancausecelllysis,
evenbeforetheinfectionprocesscanyieldprogenyvirusparticles(‘lysisfrom
without’).
Iftoofewbacteriophagesareusedfortheinfection,itmaybedifficultto
detectormeasuretheresponsebeingtested.
Thebacteriophagetocellratioiscalledthemultiplicityofinfection(moi).

3. A0.1mLaliquotofabacteriophagestockhavingaconcentration
of4X10
9
phage/mLisaddedto0.5mLofE.colicellshavinga
concentrationof2X10
8
cells/mL.Whatisthemoi?
First, calculate the total number of bacteriophage and the total number of bacteria.
Total number of bacteriophage:
0.1mL X 4x10
9
phage/ml = 4 X10
8
bacteriophage
Total number of cells:
0.5mL X 2x10
8
cells/ml =1 x 10
8
cells

4. The moi is then calculated as bacteriophage per cell:
moi = 4 x 10
8
phage / 1x 10
8
cells
= 4 phage/cell
Therefore, the moi is 4 phage/cell.

5. Reference
Calculations for molecular biology and Biotechnology –A Guide to mathematics in
the laboratory, Second Edition –Frank. H. Stephenson
11-09-2021Dr.SS
[email protected]

6. 11-09-2021Dr.SS