  We consider for the first time the implications on the modified gravity MOND
model of galaxies, of the presence of dark baryons, under the form of cold
molecular gas in galaxy discs. We show that MOND models of rotation curves are
still valid and universal, but the critical acceleration a0 separating the
Newtonian and MONDian regimes has a lower value. We quantify this modification,
as a function of the scale factor c between the total gas of the galaxy and the
measured atomic gas. The main analysis concerns 43 resolved rotation curves and
allows us to find the best pair (a0 = 0.96 10e-10 m.s-2, c = 3), which is also
compatible to the one obtained from a second method by minimizing the scatter
in the baryonic Tully-Fisher relation.
