The Role of the Bacterial Community of an Agroecosystem in Simazine Degradation

Abstract

The use of pesticides and fertilizers in agricultural practice is the main source of soil and groundwater contamination. S-Triazines are among the most used herbicides in the world for selective weed control in several types of crops. The homeostatic capability of an agroecosystem to remove a triazinic herbicide, simazine, was assessed in microcosms treated with the herbicide in presence/absence of urea fertilizer. The latter, as well as a fertilizer, is also one of the last by-products before simazine mineralization. The biodegradation, in terms of disappearance of 50% of the initial concentration (DT 50 ), was compared to the degradation and metabolite formation occurring in sterilized soil. Moreover, the bacterial community response was assessed in terms of abundance and community structure by the epifluorescence direct count method and fluorescence in situ hybridization. The results show that the microbial community has a primary role in simazine degradation and that this process is due to the presence of a microbial pool working in succession and of which the metabolism may be modulated by exogenous sources of nitrogen, like urea. The latter influences the degradative pathway with a greater formation and accumulation of the desethyl-simazine metabolite, which is a hazardous contaminant of soil and groundwater ecosystems, as well as its parent compound.

Application of a simazine degrading bacterium, Arthrobacter ureafaciens XMJ‐Z01 for bioremediation of simazine pollution

“…Because the strain XMJ‐Z01 is an obligate aerobic bacterium, it is easier to survive on the surface of the soil, and the deep soil layer is not suitable for its growth due to low oxygen content (Bazhanov et al , 2017; Zhao et al , 2020). In the control group (0–3 cm), the residual concentration of simazine is significantly reduced, which may be mainly due to the degradation of simazine by natural microorganisms in the soil (Caracciolo et al , 2007; Marcela et al , 2010). At the same time, there may be a small amount of simazine leaking into the subsoil, because the concentration of simazine in the control group (15 or 25 cm) is not significantly reduced, even a small increase.…”

“…There is no commercially available microbial agent for the bioremediation of simazine contamination. Thus, it is still necessary to screen the simazine‐degrading strains with excellent performance and to investigate their degradation characteristics in order to remove simazine from the simazine‐contaminated environment (Caracciolo et al , 2007).…”

Isolation of 2 simazine-degrading bacteria and development of a microbial agent for bioremediation of simazine pollution

“…However, the degradation efficiencies of the simazine-degrading strains were not satisfactory in most cases, and no simazine-degrading strain has been used for commercial purposes. Therefore, in order to solve the environmental problems caused by simazine pollution, it was necessary to isolate high-efficiency simazine-degrading strains and study their degradation characteristics (Caracciolo et al 2007).…”