# Permethrin Insecticide Influence on Microorganisms Present in Surface Waters
## 4 Discussion  
The results obtained in the course of this study provide a perspective on the effects of permethrin on microorganisms present in surface waters extracted from various ecosystems. Pronounced toxicity against the tested microorganisms was observed only at a concentration of 100 ppm for both consortia and strain _Serratia fonicola_ PS. At 1000 ppm, the permethrin was toxic to all consortia and strains, excluding _Bacillus thuringiensis_ KlaKry. Moreover, permethrin did not adversely affect bacterial metabolism. Nevertheless, it was observed that in the case of bacteria from a protected area (Snowy Ponds), higher concentrations of the insecticide lowered the metabolism of carboxylic acids. The toxicity results obtained correspond to those obtained for soil strains. [PERSON] et al. [19] determined that for _Enterobacter ludwigii_ (VITSPR1), considered a plant growth-promoting rhizobacteria, the growth-inhibiting concentration of permethrin was above 50 ppm. In contrast, [PERSON] et al. [20] found that permethrin at a concentration of 80 ppm stimulated the multiplication of cultured organotrophic bacteria (by 38.3% on average) and actinomycetes (by 80.2% on average). So, the concentrations recommended by the manufacturer (around 600 ppm) may already be dangerous to soil microorganisms, although lower concentrations may even have a positive effect on microbial growth. The effect of the insecticide on cell properties was also studied. This first concerned the hydrophobicity of the cell surface. This parameter clearly decreased with increasing permethrin concentrations, so the cell surface became more hydrophilic. At the same time, permethrin was found to increase the permeability of the membrane and cell wall of bacterial cells. Both of these parameters, although not necessarily directly correlated with the associated toxicity, very strongly influence the bioavailability of organics to bacterial cells. Greater surface hydrophilicity facilitates the absorption of hydrophilic substances [21]. This is also important in the context of the degradation of pesticides themselves. As [PERSON] et al. [22] found, comparing strains of the _Serratia_ genus with different cell surface hydrophobicity, the higher the hydrophobicity, the more effective the biodegradation of beta-cypermethrin. Similarly, the greater the permeability of the cell membrane, the greater the absorption of compounds from the environment, but at the same time, the less stable the homeostasis in the cell [23]. Membrane permeability, changed, e.g., by surfactants, is one of the main parameters influencing the biodegradation and toxic effects of xenobiotics in the environment (not only pesticides) [21]. The crystal violet assay was used to investigate changes in cell membrane permeability. The absorbance of samples containing permethrin was measured, and the result was compared with the absorbance of control samples. From what we observed in our study, permethrin caused a disruption of the membrane structure of tested strains, which can allow toxic substances to enter the cell more easily, leading to cell dysfunction or death. In conclusion, while permethrin may not be highly toxic, it can be expected that it may act to increase the susceptibility of bacteria to the presence of other toxins. However, the threat to environmental microflora from the use of permethrin will depend on abiotic and biological factors regulating its bioavailability [24]. Pyrethroids are more persistent in the environment compared to natural pyrethrins. This also applies to permethrin, which is described as resistant to light. It is also stable in acidic environments. However, an alkaline environment promotes the hydrolysis of this compound [25]. Microorganisms capable of biodegradation permethrin are also present in the environment,such as _Acinetobacter baumanni_ ZH-14 described by [PERSON] et al. [26]. However, the half-life of permethrin in the soil ranges from a few hours to a few days, meaning soil microorganisms will be exposed to permethrin for at least several weeks.