FIG 2.
Impact of the specific rhizosphere nutritional context on early surfactin production. (a) Evaluation of bacterial population (black line, left axis) and relative srfAA expression on roots (gray bars, right axis) in a time frame of 7 days postinoculation (dpi). Bacillus progression on roots characterized by a biofilm formation was assessed by microscopy at each time point (top part). (b) Surfactin production rate on roots. Means ± SE from three biological replicates of one experiment are shown. (c) Surfactin accumulation measured by UPLC-MS in a 8-h time course experiment in REM medium (gray bars) compared with that in LB medium (red bars). Means ± SE from three biological replicates of one experiment are shown ***, P < 0.001; **, P < 0.01; *, P < 0.05. (d) Comparison of early surfactin accumulation (μM of surfactin on y axis linked to OD600 on x axis) in different Bacillus species, including B. velezensis (GA1 and S499 in green), B. pumilus (QST 2808 in orange), B. amyloliquefaciens (DSM 7 in red), and B. subtilis (ATCC 21332 in blue). Circle symbols represent plant-associated bacteria, whereas triangle symbols represent non-plant-associated bacteria.