Excessive use of thifensulfuron-methyl has raised concerns for environmental contamination and phytotoxicity to crops. Experiments were performed to isolate a microorganism that can degrade thifensulfuron-methyl and assess its effectiveness.A bacterial isolate, Ochrobactrum sp. ZWS16, capable of degrading thifensulfuron-methyl was studied. The half-life for thifensulfuron-methyl was less than 6 days in liquid medium after addition ZWS16 (5–400 mg thifensulfuron-methyl/l). Maximum biodegradation was 99.5 % for 50 mg thifensulfuron-methyl/l at 40 °C over 10 days. Of the five metabolites from the degradation of thifensulfuron-methyl that were identified, methyl 3-(N-carbamoylsulfamoyl) thiophene-2-carboxylate and 3-[(formimidoylamino-hydroxy-methyl)-sulfamoyl)-thiophene-2-carboxylic acid are reported for the first time. The degradation pathways might proceed via cleavage of the sulfonylurea bridge, O-demethylation, de-esterification and cleavage of the triazine ring. The removal of thifensulfuron-methyl was 58 % after inoculation of strain ZWS16 into sterilized soil. Strain ZWS16 can also degrade nicosulfuron, tribenuron-methyl, pyrazosulfuron-ethyl, metsulfuron-methyl and triasulfuron.Addition of strain ZWS16 to both liquid medium and sterilized soil accelerated the degradation of thifensulfuron-methyl. Strain ZWS16 might therefore be useful in removing thifensulfuron-methyl contamination in water and soil.

NADH-cytochrome b5 reductase (CBR) is one of the most important components of cytochrome P450s, which play an essential role in the detoxification of xenobiotics as well as insecticide resistance in insect pest. In the present study, two novel full-length cDNAs of CBR of the cotton bollworm, Helicoverpa armigera (Hübner) were amplified by means of reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) techniques. The sequencing results showed that the transcripts were 1809 bp and 1518 bp for HaCBR1 and HaCBR2, respectively, including 969 bp and 939 bp of complete open reading frame (ORF), which encoded 322 and 312 amino acids respectively. The putative structure and function of HaCBR1 and HaCBR2 were preliminarily analyzed by SMART program.HaCBR1 and HaCBR2 (GenBank accession numbers: HQ638220 and HQ190046HQ638220HQ190046) showed high identities with CBRs of other species. The expression of HaCBR1 and HaCBR2 mRNA was detected by real-time quantitative polymerase chain reaction (RT-qPCR) in most developmental stages of H. armigera with the exception of eggs, as well as in tissues such as cuticle, fatbody and midgut. The expression level of the two genes was significantly induced by phenobarbital (PB). These results would contribute to the understanding of CBR function in H. armigera and provide information for further study on the interactions of different components of cytochrome P450 enzyme systems.Highlights► Two different CBR genes were firstly cloned from H. armigera. ► Bio-information of both CBR genes was analyzed. ► Expression level of both CBR genes in different tissues was detected. ► Expression level of both CBR genes in different growth stages was detected. ► The change of expression level of both CBR genes induced by PB was examined.

A bacterial strain ZWS11 was isolated from sulfonylurea herbicide-contaminated farmland soil and identified as a potential nicosulfuron-degrading bacterium. Based on morphological and physicochemical characterization of the bacterium and phylogenetic analysis of the 16S rRNA sequence, strain ZWS11 was identified as Alcaligenes faecalis. The effects of the initial concentration of nicosulfuron, inoculation volume, and medium pH on degradation of nicosulfuron were investigated. Strain ZWS11 could degrade 80.56% of the initial nicosulfuron supplemented at 500.0 mg/L under the conditions of pH 7.0, 180 r/min and 30°C after incubation for 6 days. Strain ZWS11 was also capable of degrading rimsulfuron, tribenuron-methyl and thifensulfuron-methyl. Four metabolites from biodegradation of nicosulfuron were identified, which were 2-aminosulfonyl-N, N-dimethylnicotinamide (M1), 4, 6-dihydroxypyrimidine (M2), 2-amino-4, 6-dimethoxypyrimidine (M3) and 2-(1-(4,6-dimethoxy-pyrimidin-2-yl)-ureido)-N,N-dimethyl-nicotinamide (M4). Among the metabolites detected, M2 was reported for the first time. Possible biodegradation pathways of nicosulfuron by strain ZWS11 were proposed. The degradation proceeded mainly via cleavage of the sulfonylurea bridge, O-dealkylation, and contraction of the sulfonylurea bridge by elimination of a sulfur dioxide group. The results provide valuable information for degradation of nicosulfuron in contaminated environments.Download high-res image (80KB)Download full-size image