  We study the hydrodynamic properties of strongly coupled SU(N) Yang-Mills
theory of the D1-brane at finite temperature in the framework of gauge/gravity
duality. The only non-trivial viscous transport coefficient in 1+1 dimensions
is the bulk viscosity. We evaluate the bulk viscosity by isolating the
quasi-normal mode corresponding to the sound channel for the gravitational
background of the D1-brane. We find that the ratio of the bulk viscosity to the
entropy density to be 1/4\pi. This ratio continues to be $1/4\pi$ also in the
regime when the D1-brane Yang-Mills theory is dual to the gravitational
background of the fundamental string. Our analysis shows that this ratio is
equal to 1/4\pi for a class of gravitational backgrounds dual to field theories
in 1+1 dimensions obtained by considering D1-branes at cones over
Sasaki-Einstein 7-manifolds.
