Figure 2.

Schematic representation of interactions identified among pneumococcal strains. For each strain growing in a dual-strain biofilm three possible effects can be observed when its cell counts are compared to those obtained when growing alone (single-strain biofilms depicted on the left): negative (-), if there is a decrease in its cell counts; positive (+), if there is an increase in its cell counts; and neutral (0), if there is no change. Depending on the combination of effects observed for each pair of strains, interactions can be divided into six categories: neutralism (0/0), mutualism (+/+), commensalism (+/0), antagonism (-/+), amensalism (-/0) and competition (-/-) [reviewed in (Faust and Raes, 2012)]. The interaction observed for each pair of strains is indicated below the schematic representation of each interaction.