Fig. 2.

Bacterial attraction towards VOCs in soil. a A glass olfactometer system with four different treatments in the central vessel: control (only soil); soil with F. culmorum; Carex, and Carex with F. culmorum. Connected glass tubes contained soil mixed with (+ARE) or without artificial root exudates (no ARE). A synthetic bacterial community including Burkholderia sp. AD024, Dyella sp. AD056, Janthinobacterium sp. AD080, Paenibacillus sp. AD087, Pseudomonas sp. AD021, and Collimonas pratensis Ter91 was inoculated into soil at one end of the glass tube. After 65 h soil was collected at 0.8 cm distance from the connection part to the central vessel (i.e. 3.8 cm distance from the inoculation point) (a) to quantify the migrated bacteria. Drawing is not true to scale. b Bacterial number obtained by qPCR of the 16S rRNA gene at the collection area. 16S rRNA gene copy numbers were transformed into cell number based on the known copy number of the gene per genome. Different letters represent significant differences between the four treatments. Gray dotted line indicates initial bacterial concentration added at the inoculation point. H_i, height of inner filling area, L_i length of inner filling area, VOCs volatile organic compounds