Bacterial species seem to compete more than they cooperate.

Kevin Foster at the University of Oxford, UK, and Thomas Bell at Imperial College London tested the theory that different bacterial species can form cooperative 'superorganisms'. The team measured the productivity — in terms of CO2 given off through respiration — of a range of multi-species microbial cultures. After both one week and one month, species in the mixtures were less productive than they would have been if grown separately, suggesting that social living comes at a cost.

Curr. Biol. http://dx.doi.org/10.1016/j.cub.2012.08.005 (2012)