The ecological hazards of profenofos revealed by soil beneficial-bacteria, plant seedlings, and plasmid nicking assays: A short-term toxicity investigation

Abstract

Excessive and indiscriminate use of pesticides may adversely affect the growth and activity of both crop plants and soil microbial populations. The reported study was conducted to evaluate the toxicity of profenofos (PF; an organophosphate insecticide) using bacterial (Pseudomonas fluorescens PSB-3 and Enterobacter cloacae ZSB-8) and plant (Coriandrum sativum and Lactuca sativa L.) bioassays. PF was applied at rates of (0–100 µg mL⁻¹) in vitro. Both bacterial strains were sensitive to PF but showed variable tolerance. Following PF exposure, cellular growth, morphology, survival, and inner membrane permeability of bacterial strains were significantly (p < 0.05) altered. Decreased population size coincided with decline in cellular respiration. The 100 µgmL⁻¹ PF dosage imparted maximum impact on ZSB-8, inhibiting populations by 87%. PF also interfered with bacterial surface adherence (i.e., biofilm formation) in a concentration-dependent manner. Alterations in bacterial biomarker enzymatic activity and oxidative stress were also noted. PGP traits of bacterial strains were negatively and significantly (p ≤ 0.05) affected by insecticide. Under PF stress, reduction in indole-3-acetic and siderophore production followed the order: ZSB-8 > PSB-3. PF-induced phytotoxicity was confirmed via reduction in germination, seedling parameters, survival, tolerance, and vigor indices in both plant species. Additionally, PF caused distortion in morphology of root tips and root surfaces. Under CLSM, PF-exposed C. sativum and L. sativa roots exhibited increased oxidative stress. Cellular death in insecticide-treated roots was observed following staining with Evans blue dye. Insecticide concentration-dependent increase in stress markers (proline and MDA content), and antioxidant enzymatic activities in plant seedlings were observed. A dose-dependent conversion of super-coiled form of DNA to open circular in pBR-322 plasmid revealed the genotoxic potential of PF. These findings provide an understanding of toxic effects of profenofos on beneficial microbes and leafy edible vegetables, including their morphological, and cellular effects. Indeed, insecticidal applications deserve special attention due to their potential environmental hazards.