Abstract
Bacterial strain FH-1 with high efficiency of degrading Atrazine is separated by means of enrichment culture from the soil applied with Atrazine for many years. FH-1, recognized as Klebsiella variicola based on phylogenetic analysis of 16S rDNA sequences, can grow with Atrazine which is the sole nitrogen source. In fluid inorganic salt medium, the optimal degradation temperature, pH value, and initial concentration of Atrazine are 25°C, 9.0, and 50 mg L–1, respectively, and the degradation rate of Atrazine by strain FH-1 reached 81.5% in 11 d of culture. The degrading process conforms to the kinetics equation of pesticide degradation. Among the metal ions tested, Zn2+ (0.2 mM) has the most significant effect of facilitation on the degradation of Atrazine. In the fluid medium with Zn2+, the degradation rate of Atrazine is increased to 72.5%, while the Cu2+ (0.2 mM) inhibits the degradation of Atrazine. The degradation products of Atrazine by strain FH-1 were identified as HEIT (2-hydroxyl-4-ethylamino-6-isopropylamino-1,3,5-triazine), MEET (2-hydroxyl-4,6-bis(ethylamino)-1,3,5-triazine), and AEEO (4,6-bis(ethylamino)-1,3,5-triazin-2(1H)-one) by HPLC-MS/MS. Three genes (atzC, trzN, and trzD) encoding for Atrazine degrading enzymes were identified by PCR and sequencing in strain FH-1. This study provides additional theoretical support for the application of strain FH-1 in bioremediation of fields polluted by Atrazine.
Highlights
Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5triazine) is one of the globally used triazine herbicides [1, 2], which is applied to control weeds in sorghum, corn, and sugarcane fields [3, 4]
These results showed that the degradation of Atrazine by strain FH-1 was improved by adding appropriate metal ions to the inorganic salt medium
Results of our studies demonstrate that the Klebsiella variicola strain FH-1 is capable of effectively degrading Atrazine
Summary
Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5triazine) is one of the globally used triazine herbicides [1, 2], which is applied to control weeds in sorghum, corn, and sugarcane fields [3, 4]. Because of its high water solubility, long residual time, and being difficult to decompose, Atrazine can pollute the groundwater and cause damage to the succession crops and animals as well [5]. It is reported that 5% of Atrazine runs off with soil due to rainfall and irrigation and flows into aquatic ecosystem in the entire drainage basin [6]. Atrazine influences sex differentiation hormones in red claw crayfish during their early developmental stages and causes endocrine disorders, resulting in increased proportion of females in offspring [7]. Atrazine is reported to affect the immune system of rabbits [8]. Atrazine has been reported to affect the formation of hemoglobins in humans [9]. Considering the wide application and high toxicity of Atrazine, it is of great importance to seek a practical way to rehabilitate the polluted environment caused by Atrazine
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