Team:Goettingen/Demonstrate

Real life conditions

Until now our detection method worked perfectly under laboratory conditions, so the next step was inevitably to test it under “real life conditions”, or more precisely, we put our method under trial. Hence, we purchased the product Roundup® from our local home improvement store. It has to be considered, that even though glyphosate is the active ingredient in Roundup®, it contains additional substances that could pose negative side effects. In a first trial phase, we wanted to investigate if Roundup® affects our modified Bacillus strains in a similar way as pure glyphosate (Figure X).

Figure X: Growth curves from the Bacillus subtilis wildtype strain 168 with increasing amounts of the herbicidal mixture Roundup®. The optical density was measured at λ=600 nm.

Indeed, the strain shows similar behaviour in the presence of Roundup® like with pure glyphosate!

Furthermore, we repeated our competition experiments with Roundup® and compared it to our previous results. The signals from GFP and mOrange fit with the experiments where pure glyphosate was used.

Figure X: This figure shows the effects of Roundup® on the competition assay we performed previously. The fluorescence of GFP is shown on the ordinate, the abscissa depicts the time. GFP was excited at λ=488 nm and emission was measured at 509 nm. mOrange was excited at λ=529 nm, emission was recorded at λ=562 nm.
A: Fluorescence of GFP. With increasing amounts of Roundup®, the fluorescence of GFP decreases.
B: Fluorescence of mOrange. With increasing amounts of Roundup®, the fluorescence increases.

This results show that our detection method works perfectly with the commercially available product Roundup®!

The overall aim of our project was to devise a procedure that allows to determine if a sample is contaminated with glyphosate. Consequently we analysed soil samples that were previously treated with Roundup®. Our product is based on the intraspecies competition of a sensitive strain expressing constitutively the β–galactosidase and a glyphosate-resistant strain. In the following figure, the function of our product is depicted (Figure X).

Roundup® is sprayed on soil. Then, water is applied to solve the glyphosate from the sample. The solution is filtered through a filter device to avoid any other contaminations like other microorganisms. The sample drops onto solid media powder with all necessary ingredients and Bacillus subtilis spores from the two competing strains. The sample is incubated for 10 h at 37°C with agitation. Now, the blue color can be compared to a test strip. The intensity of the blue color determines the concentration of glyphosate in the sample.

The usage of our product is also shown in the following movie.

VIDEO!!!