# Effect of Pseudomonas Fluorescens on Isofetamid Dissipation and Soil Microbial Activity
## 4 Discussion
### Effect of P. fluorescens and Isofatamide on Soil Enzyme Activity and Microorganism Abundance  
The activity of soil microorganisms and enzymes is of great importance in maintaining soil health and ensuring its fertility and productivity [41]. Soil enzymes participate in the cycling of C and other plant nutrients. B-Glu participates in the decomposition of cellulose and provides labile forms of C. N-Ac decomposes chitin and releases N; PP is an enzyme involved in the release of organic phosphorus to free phosphates. Another enzyme, AS, is necessary to catalyze organic sulfur compounds' hydrolysis [42; 43]. The literature data indicate that fungicides can disturb the microbiological activity of soil expressed by the number of different microbial communities and the activity of soil enzymes [7; 44]. Soil enzymatic activity is a very sensitive parameter to any changes occurring in the soil environment. As a result of enzyme testing, even the smallest fluctuations related to the activity of microorganisms after the application of pesticides or other xenobiotics can be detected. This parameter also provides insight into soil health and corresponds to the condition of the indigenous microbial population. Changes in activity between individual enzymes in our studies were the result of the different effects of IS and IS+P on the microorganisms living in the soil. Other groups of microorganisms may participate in the secretion of individual enzymes, on which IS can have either a stimulating or inhibiting effect, which translates into an increase or decrease in activity [7; 44]. There is also evidence that some enzymes such as \(\beta\)-glucosidase and acetylglglucosamine are not sensitive to the presence of fungicides [45]. Our studies showed only a negative average correlation between the concentration of IS and the activity of \(\beta\)-Glu. For the remaining enzymes, no significant correlations were found between the concentration of isofetamid in the soil. Our study also showed that the activity of soil enzymes was variable over time and, at the beginning of the experiment, it was observed that in the variants IS and IS+P, the activity was similar to that in the control. The increase in activity on D21 (mainly of \(\beta\)-Glu and PP) can be explained by a decrease in the toxicity of the pesticide due to its decomposition by microorganisms that use xenobiotics as a carbon and energy source. Moreover, the activity of soil enzymes is a result of various biotic and abiotic factors, including the physicochemical properties of the soil such as pH, TOC, soil temperature and moisture, and N and P content. The structure of the pesticide and its properties are also important. In our studies, it was also observed that IS and IS+P applications significantly increased AS activity in the soil. The increase in AS activity in the soil may have been because isofetamid contains sulfur, which could be a substrate for this enzyme. However, according to [PERSON] et al. [43], pesticides containing sulfur, oxygen or nitrogen in the ring are decomposed by microorganisms slower than aromatic, aliphatic or hydroxyl compounds. Considering the abundance of soil microorganisms, it was observed that IS mainly affected the abundance of archaea and AOB. These are groups of microorganisms considered important in the biogeochemical cycle [23; 46]. According to [PERSON] et al. [47], pesticides can inhibit the nitrification process and, therefore, the activity and abundance of microorganisms responsible for ammonia monooxygenase. It has recently been shown that archaea can also be involved in this process. In our study, on both sampling dates, the number of archaea and amoA genes was lower than in the control. Moreover, Pearson correlation analysis showed a negative relationship between the concentration of IS and the abundance of archaea and AOB genes.