Vehicles, Replicators, and Intercellular Movement of Genetic Information: Evolutionary Dissection of a Bacterial Cell

Table 1

Classification of replicators.

Class	Example replicators	Vertical dependency	Horizontal movement potential	Description of average phenotypes
I	Prokaryotic chromosomes	Completely dependent	No potential	Encodes the main functional units of all cell vehicles. Required for the binary fission of the cell vehicle.
II	Plasmids, transposons	Highly dependent	Passive	Low reproductive cost to host cell vehicle. Can encode opportunistically useful phenotypic traits.
III	Conjugative plasmids, integrative and conjugative elements (ICEs)	Moderately dependent (always requires a cell vehicle)	Active without an extracellular stage	Moderate or low reproductive cost to host cell vehicle. Usually encode opportunistically useful phenotypic traits.
IV	Temperate viruses	Somewhat dependent (can survive even if the cell-vehicle terminates)	Active with an extracellular stage	Moderate or low reproductive cost to host cell vehicle. Sometimes encode opportunistically useful phenotypic traits.
V	Virulent viruses	Not dependent	Active with an extracellular stage	Insurmountable reproductive cost that terminates the host cell vehicle. Does not encode cell-vehicle benefitting traits.