jan weber, anke kayser, and ursula rinas, performed an experiment to test what happened to the methylglyoxal pathway when "e. coli" was in the presence of a constantly high concentration of glucose. the concentration of methylglyoxal increased until it reached 20 μmol. methylglyoxal concentration then began to decrease, once it reached this level. the decrease in the concentration of methylglyoxal was connected to the drop in respiratory activity. when respiration activity increased the concentration of methylglyoxal increased again, until it reached the 20 μmol concentration (weber 714-15).