  We cast the metabolism of interacting cells within a statistical mechanics
framework considering both, the actual phenotypic capacities of each cell and
its interaction with its neighbors. Reaction fluxes will be the components of
high-dimensional spin vectors, whose values will be constrained by the
stochiometry and the energy requirements of the metabolism. Within this
picture, finding the phenotypic states of the population turns out to be
equivalent to searching for the equilibrium states of a disordered spin model.
We provide a general solution of this problem for arbitrary metabolic networks
and interactions. We apply this solution to a simplified model of metabolism
and to a complex metabolic network, the central core of the \emph{E. coli}, and
demonstrate that the combination of selective pressure and interactions define
a complex phenotypic space. Cells may specialize in producing or consuming
metabolites complementing each other at the population level and this is
described by an equilibrium phase space with multiple minima, like in a
spin-glass model.
