Fig. 1: The modified bead-transfer model procedure and culture dynamics of Lactococcus lactis and Leuconostoc mesenteroides during 16 days of cultivation.

A In the bead transfer model, L. lactis and L. mesenteroides were cultured individually or together on glass beads. After 24 h of cultivation, a bead with attached biofilm was washed three times and moved to a new container with labeled glass beads (marked with dots). Bacterial cells were allowed to disperse and attach to the new labeled beads for 24 h before transfer. At every third transfer, a single bead was sonicated to release and disperse biofilm cells for CFU quantification and isolation of evolved strains (Illustration created with Biorender.com). B Relative abundance of L. lactis in co-cultures with L. mesenteroides at day 16 in the bead-transfer model and planktonic-transfer model. The relative abundance of L. lactis was significantly higher in the bead-transfer model at day 16 compared to planktonic-transfer (P = 0.0056, Wilcoxon Rank-Sum test). C Cell counts of L. lactis and L. mesenteroides for mono- and co-cultures throughout the duration of the bead transfer experiment. Numbers of L. mesenteroides were unaffected by the co-cultivation (P > 0.05, Welch Two Sample t test), except for day 1 and 13 (P = 0.004 for both, Welch Two Sample t test), when comparing mono- and co-culture populations, whereas the number of L. lactis were reduced by co-cultivation compared to mono-cultivation (P < 0.05, Welch Two Sample t test, except day 10 where P = 0.33). Graph depicts means and 95% confidence intervals as solid lines and ribbons, respectively. Five biological replicates (lineages) were included. N = 5.