Effect of inert ingredients in pesticide formulations on a soil Betaproteobacterium

The inert ingredients in pesticide formulations are known to cause a range of health problems to humans and animals however the effects of these formulations on soil bacteria have not been studied. Soil bacteria help maintain a healthy soil and provide microorganisms and plants with nutrients they need for growth and development. If the pesticide formulation is toxic to the soil bacteria, it can adversely affect the plants and the soil quality. Here, we investigated whether the inert ingredients in pesticide formulations, which are available over the counter, are toxic to soil microorganisms as compared to the pesticide itself. Growth studies were performed by taking optical density measurements of bacterial cultures over time. We treated the bacterial culture with 1.2mM concentration of pure pesticide as well as 0.7mM concentration of the over-the-counter formulation. The results show that almost half the concentration of the over-the-counter formulation is bacteriostatic towards soil bacteria compared to the pure reagent grade pesticide. These findings suggest that over-the-counter pesticide formulations are toxic to non-target soil bacteria, in a way that they increase the lag period of the growth cycle. Also, it hints that the toxicity is caused not by an active component but the inert components of the pesticide formulation mixture. The results obtained from the experiments carried out using the cells obtained from the growth curves, indicate that the bacteria are probably adjusting to the concentration of the pesticide formulation during the extended lag phase and hence normal growth curve is seen when the pre treated cells are treated with the same concentration of the formulation again. This thesis suggests a possible toxicity to soil microorganisms due to pesticide formulations and the resulting damage to agricultural industry.