Figure 5. Benzoate utilization may impact the bacterial lifestyle switch.

(a) Presence of benzoate transport and degradation genes in genomes of phytoplankton-associated Proteobacteria. Emiliania huxleyi-associated bacteria are denoted. Colored tiles depict the presence of the genes. Bacterial strains highlighted in bold possess genes for both transport and degradation of benzoate. Bacterial benzoate degradation pathways are elaborated in Figure 4—figure supplement 1. The full data of the presence of all query genes in the genomes of the bacteria is presented in Figure 5—source data 1. The query genes are listed in Key resources table. (b) Bacterial growth after 24 hr in minimal media with no carbon source or supplemented with 100 µM benzoate or succinate, as a sole carbon source, of Sulfitobacter D7 (yellow) and two additional Sulfitobacter strains (Sulfitobacter pontiacus DSM 10014 [green] and Sulfitobacter brevis DSM 11443 [blue]) that do not possess the genes required for benzoate utilization. Results represent average ± SD (n=3). Statistical differences were tested using two-way analysis of variance, followed by Tukey’s post-hoc test. * p-Value <0.05, ** p-value <0.01 *** p-value <0.0001. (c) Time course of E. huxleyi CCMP379 and bacterial abundance (left and right panels, respectively) in algal mono-cultures (gray) or during co-culturing with Sulfitobacter D7 (yellow), S. pontiacus (green), or S. brevis (blue). Results represent average ± SD (n=3). Statistical differences were tested using repeated-measures analysis of variance, followed by a Tukey post hoc test. p-Value <0.0001 for the difference in E. huxleyi and bacterial growth between all treatments, except for E. huxleyi growth in the treatments ‘+S. pontiacus’ compared to ‘+S. brevis’, which was not significant.