Influence of the insecticides profenofos and diazinon on the microbial activities of Azospirillum brasilense

The influence of 10, 50, 100, 200 and 300 μg/ml of profenofos and diazinon were investigated in cells of Azospirillum brasilense grown in chemically-defined medium and dialysed-soil medium. The insecticide diazinon did not affect microbial growth, levels of ATP, dinitrogen fixation and production of vitamins of A. brasilense in either chemically-defined medium or dialysed-soil medium. Profenofos significantly reduced dinitrogen fixation, intracellular levels of ATP, production of pantothenic acid, thiamine, niacin and growth in cells grown in chemically-defined medium. However, these negative effects were not significant in cells grown in dialysed-soil medium, suggesting that application of profenofos to culture medium was not detrimental to A. brasilense under the present experimental conditions.