Question

How does bacteriophage P1 cope with partition and maintenance of a low copy number

Answer 1

P1 is a bacteriophage of Escherichia coli and some enteric bacteria. It lysogenizes its hosts as a circular, low-copy-number plasmid.

P

Partition of bacteriophage Pl can be thought of as a. positioning reaction.; the plasmid - encoded components. ensure that at least one copy of the plasmid is. positioned within each new daughter cell. The partition system of the low copy number plasmid/ prophage of bacteriophage Pl encodes two proteins, Par A and Par B. and contains a DNA site called Pars. Par B and and the THE (integration host factor) bind to. Pars to form the partition complex ; in which parsis. wrapped around Par B and THE in a precise 3-dimensional conformation They cannot rely on random segregation during bacterial cell division. To be stably maintained in population they evolved two types of mechanisms. (i) partition systems (PAR) that actively separate. replicated plasmid molecules to daughtercell's (11) toxin-antidote systems (TA) that act after cell. division to kill plasmid less cells. It maintains a low copy number bacterium, as the plasmid encodes a plasmid addiction. plasmid in the system that kills daughter cells that lose the plasmid.

Plasmids of low copy number,(especially P1 prophage), are actively partitioned to nascent daughter cells. The process is mediated by a pair of plasmid‐encoded proteins and a cis‐acting DNA site , referred to as the plasmid centromere