Enhanced microorganism swimming in active matter

Microorganisms swim through the fluid by periodically deforming their body. We study the
swimming dynamics of micro-organisms modeled as a Taylor sheet or squirmer in the isotropic
phase of an active nematic liquid crystal. The activity changes the effective viscosity of the fluid,
reducing it to zero at a critical value of activity [Hatwalne et al., Phys. Rev. Lett. 92, 1181018
(2004)]. We find that the correction to the swimming speed due to the presence of active nematic
molecules is inversely proportional to the viscosity. Thus the swimming speed diverges at the critical
value of the activity, though the correction for the passive nematic liquid crystal is negligibly small
for the parameter range belonging to the real experiments.