Bacteria form complex communities in which they interact, and interspecies interactions can lead to the emergence of new traits. Silby and colleagues co-cultured two distantly related soil bacteria, Pseudomonas fluorescens Pf0-1 and Pedobacter sp. V48, and found that a mixed colony spreads across a hard agar surface, whereas either species was immotile in monoculture. This suggests that the presence of the two species leads to changes in behaviour. The author termed this mode of co-migration interspecies social spreading. They showed that physical association of both species is required for interspecies social spreading and that both species remain associated throughout the spreading colony. Finally, interspecies social spreading was observed on low-nutrient media supplemented with sodium chloride, whereas spreading was reduced or absent on low-nutrient media without salt supplementation or on rich media, respectively.
McCully, L. M. et al. Interspecies social spreading: interaction between two sessile soil bacteria leads to emergence of surface motility. mSphere https://doi.org/10.1128/mSphere.00696-18 (2019)