Team:Goettingen/Results

Identification of glyphosate uptake systems

Interaction between glyphosate and Bacillus subtilis

To create a proper detection system using the Gram-positive model bacterium Bacillus subtilis, we first had to evaluate how this organism grows in the presence of glyphosate. Previously, it was shown that glyphosate negatively affects growth of B. subtilis due to the inhibition of the EPSP synthase AroE (Figure 1A) (1). Moreover, it has been demonstrated that 1.8 mM of glyphosate was required to inhibit the growth rate by 50%. To re-evaluate the effect of glyphosate on growth of our B. subtilis laboratory strain 168, we performed growth experiments in CS-Glc minimal medium that was supplemented with increasing amounts of glyphosate. CS-Glc medium contains glucose and succinate as carbon sources and ammonium as the nitrogen source (see Notebook). As shown in Figure 1B, at a glyphosate concentration of about 1 mM the growth rate was reduced by 50% and the bacteria were not able to grow at glyphosate concentrations higher than 3 mM. In contrast to a previous study (1), this study revealed that 44% fewer glyphosate is required to reduce the growth rate of B. subtilis by 50%. This discrepancy might be due to differences in the genetic makeup of the B. subtilis strains, in the medium composition, in the purity of glyphosate or due to the different cultivation conditions. However, glyphosate negatively affects growth of B. subtilis in CS-Glc minimal medium.

Figure 1. (A) Glyphosate (GS) inhibits the 5-enolpyruvyl-shikimate-3-phosphate (EPSP) synthase in B. subtilis. (B) Inhibition of B. subtilis by GS.

Genomic adaptation of Bacillus subtilis to glyphosate

To create a proper detection system using the Gram-positive

References

  1. Fischer et al. (1986) J. Bacteriol. 168: 1147-1154
  2. Zaprasis et al. (2015) Appl. Environ. Microbiol. 81: 250-259.