Effect of non-ionic tensides on the growth of some soil bacteria

The effect of some nonylphenyl-ethylene oxide polymers on the growth of Bacillus megaterium, B. cereus var. mycoides, B. polymyxa, B. subtilis, Pseudomonas fluorescence and Azotobacter chroococcum was investigated in the concentration range 20-800 ppm with the agar diffusion method. The zones of inhibition, restricted growth and eventual stimulation were determined with a Shimadzu C-930 dual wavelength TLC scanner. The data matrix was evaluated by principal component analysis. A. chroococcum was insensitive to each tenside at each concentration. The growth of the other microorganisms was inhibited by the tensides. With B. megaterium and B. cereus var. mycoides stimulation was also observed. The effect of the non-ionic tensides decreased with increasing length of the hydrophilic ethylene oxide chain. This phenomenon can be explained by the assumption that the activity of tensides depends on their membrane-damaging effect. The bulky nonylphenyl group inserts between the apolar fatty acid chains disorganizing the membrane structure. The longer hydrophilic ethylene oxide chain modifies the distribution of tenside between the apolar and polar regions of the membrane, preferring the aqueous phase. This results in the decrease or loss of biological activity.