%%F%%: "%%F%%" can have several different related definitions:


  * An %%F plasmid%% is a  type of naturally occurring low copy number plasmid in //E. coli// that can move from one host cell to another via conjugation, a type of sex in bacteria ("F" stands for fertility). %%F plasmids%% are also referred to as simply "%%F%%"
  * %%F%%<sup>+</sup> refers to an //E. coli// strain that contains %%F%%.
  * %%F%%<sup>-</sup> refers to an //E. coli// strain that does not contain %%F%% or any of its derivatives. 
  * %%F%%<sup>'</sup> (pronounced "%%F%% prime") refers to an %%F%% derivative that contains a portion of the //E. coli// chromosome.
  * %%Hfr%% (high frequency recombination) is a strain of //E. coli// in which F has integrated into the chromosome.