Question

When an E. coli cell is infected by multiple phages, what route of infection (lytic or lysogenic) will the phages take? Why?

Answer 1

Answer:

When an E.coli cell is infected by multiple phages,they will take either lytic or lysogenic pathway.

Explanation:

When lambda phage bacteriophage infects an E.coli,it can either undergo lytic cell growth and lyse the host cell or enter lysogenic pathway.

The operator region of lac operon in E.coli contain single repressor binding site whereas the lambda operators $O_{L}$ and $O_{R}$  each contains 3 repressor binding sites ($O_{L_1} , O_{L_2},O_{L_3}$ and $O_{R_1},O_{R_2},O_{R_3}$)  that are differently occupied under different conditions.

The differential affinity of lambda repressor for the three binding sites in these operators play an important role in the maintenance of lysogenic state of lambda prophage in E.coli.

The lytic development occurs in cells infected with lambda phage that carry  $C_1$ gene.

In contrast,lysogeny will occur in bacteria that infected with lambda phage that harbor a deletion of Cro gene.