  We report on observations of CO(1-0) emission from the chemically young
starburst galaxy Mrk 109. These observations were part of a study to constrain
the O2/CO ratio in metal-deficient galaxies, which were motivated by
theoretical work that suggests the possible enhancement of the O2/CO ratio in
chemically young systems. Five low metallicity (Z < 0.5 Z(solar)) IRAS galaxies
at redshifts z > 0.02 (required to shift the 118.75 GHz O2 line away from the
atmospheric line) were searched for CO emission. We detected the CO line in
only Mrk 109. From O2 observations of Mrk 109, we achieved an upper limit for
the O2 column density abundance ratio of N(O2)/N(CO) < 0.31. These results
provide useful constraints for the theoretical models of chemically young
galaxies. We argue that either most of the molecular gas in Mrk 109 does not
reside in dark clouds (Av >~ 5), or the standard equilibrium chemistry models
are inadequate for metal-poor systems. The molecular gas mass implied by the CO
observations of Mrk 109 is M(H2) ~= 4 x 10^{9} M(sun), and the CO data are
consistent with a central starburst induced by the interaction with a nearby
companion.
