Table 1.

Comparisons between different ParA-mediated Brownian ratchet models

	Mechanochemical Brownian ratchet	DNA-relay model	Hitch-hiking model
Originally proposed cargo	Plasmid	Chromosome	Plasmid and chromosome
Proposed substrate	Nucleoid	Nucleoid	Nucleoid
Substrate dimension	2D (*)	2D (*)	>2D
Does it entail the time-delay for ParA rebinding?	Yes	Yes	Yes
Does it invoke ParA-ParB bond elasticity?	Yes	Yes	N/A
Does it describe the intrinsic cargo diffusion?	Yes	No	N/A
Does bond tethering quench cargo diffusion?	Yes	No	N/A
Does the DNA-tethered ParA diffuse extensively?	No	Yes	No
Can the ParA without being bound to DNA laterally diffuse along nucleoid?	Yes	No	Yes
Does it require pre-existing ParA gradient?	No	Yes	N/A

^(*)Although both the mechanochemical Brownian ratchet model and the DNA-relay model were originally designated for a cargo moving on a two-dimensional substrate, it remains to be tested whether and how they support directed and persistent movement along substrates of higher dimensionality.