Question

Filamentous phage

a) Only infect E. coli that have pili.
b) Only infect E. coli lacking pili.
c) Infect E. coli regardless of the presence of pili.
d) Do not infect E. coli.

Answer 1

Filamentous phages, such as bacteriophage M13, specifically infect E. coli cells that have pili. E. coli cells with the F plasmid form the F pilus, allowing them to act as donors in bacterial conjugation and making them susceptible to infection by filamentous phages.

Step-by-step explanation:

Filamentous phage only infect E. coli that have pili. An example of such a phage is the bacteriophage M13, which specifically targets E. coli cells possessing the conjugation pilus, also known as the F pilus. The F pilus is made by E. coli cells with the F plasmid (or Fertility factor), enabling these cells to act as donor during the process of bacterial conjugation. These donor cells are referred to as F+ cells.The injection of the M13 DNA into the E. coli occurs through the pilus. Once inside the cell, the single-stranded DNA molecule synthesizes a complementary strand, creating a double-stranded replicative form (RF); this process is essential for the M13 life cycle and for its usage in recombinant DNA (rDNA) technology.The phage's ability to bind and infect bacteria depends on the interaction of the virus with the pili on the bacterial surface. Thus, E. coli without pili, such as F- cells that lack the F plasmid, are not susceptible to infection by filamentous phages like M13.