Figure 2.

Effect (mean±s.e.) of volatiles of wild-type Collimonas pratensis Ter91 and two mutants (Δ2617: no terpene synthase activity; Δ3184: no phytoene synthase activity) on the activity of three protist species (a−c). Phytoene synthase mutant (Col. Δ3184) and terpene synthase mutant (Col. Δ2617) prevent production of non-volatile and volatile terpenes, respectively. Protist activity was standardized (using Z-scores) per protist species and centred on the control treatment for each species. Positive values indicate higher protist activity than in the control (that is, no bacterial volatiles), negative values vice versa. Different letters indicate significant differences among bars. Asterisks indicate significant differences from the control. For raw data see Supplementary Figure S4, for statistical analyses Supplementary Table S6.