The metabolism of neonicotinoid insecticide thiamethoxam by soil enrichment cultures, and the bacterial diversity and plant growth-promoting properties of the cultured isolates.
A soil enrichment culture (SEC) rapidly degraded 96% of 200 mg L(-1) neonicotinoid insecticide thiamethoxam (TMX) in MSM broth within 30 d; therefore, its metabolic pathway of TMX, bacterial diversity and plant growth-promoting rhizobacteria (PGPR) activities of the cultured isolates were studied. The SEC transformed TMX via the nitro reduction pathway to form nitrso, urea metabolites and via cleavage of the oxadiazine cycle to form a new metabolite, hydroxyl CLO-tri. In addition, 16S rRNA gene-denaturing gradient gel electrophoresis analysis revealed that uncultured rhizobacteria are predominant in the SEC broth and that 77.8% of the identified bacteria belonged to uncultured bacteria. A total of 31 cultured bacterial strains including six genera (Achromobacter, Agromyces, Ensifer, Mesorhizobium, Microbacterium and Pseudoxanthomonas) were isolated from the SEC broth. The 12 strains of Ensifer adhaerens have the ability to degrade TMX. All six selected bacteria showed PGPR activities. E. adhaerens TMX-23 and Agromyces mediolanus TMX-25 produced indole-3-acetic acid, whereas E. adhaerens TMX-23 and Mesorhizobium alhagi TMX-36 are N2-fixing bacteria. The six-isolated microbes were tolerant to 200 mg L(-1) TMX, and the growth of E. adhaerens was significantly enhanced by TMX, whereas that of Achromobacter sp. TMX-5 and Microbacterium sp.TMX-6 were enhanced slightly. The present study will help to explain the fate of TMX in the environment and its microbial degradation mechanism, as well as to facilitate future investigations of the mechanism through which TMX enhances plant vigor.
a Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Industrialization of Microbial Resources, College of Life Science , Nanjing Normal University , Nanjing , PR China.
Guang-Can
GC
Zhou
Ying
Y
Wang
Yuan
Y
Ma
Shan
S
Zhai
Ling-Yan
LY
Zhou
Yi-Jun
YJ
Dai
Sheng
S
Yuan
D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001673:Biodegradation, Environmental; D044822:Biodiversity; D007210:Indoleacetic Acids / Q000378:metabolism; D007306:Insecticides / Q000378:metabolism*; D008969:Molecular Sequence Data; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000378:metabolism*; D009586:Nitrogen Fixation; D010078:Oxazines / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000378:metabolism; D012336:RNA, Ribosomal, 16S; D012230:Rhizobiaceae / Q000235:genetics; D012988:Soil Microbiology; D000077922:Thiamethoxam; D013844:Thiazoles / Q000378:metabolism*
D007210:Indoleacetic Acids; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010078:Oxazines; D010937:Plant Growth Regulators; D012336:RNA, Ribosomal, 16S; D013844:Thiazoles; C030737:indoleacetic acid; D000077922:Thiamethoxam
16S rRNA gene‐DGGE; nitroreduction; plant growth‐promoting rhizobacteria; soil enrichment culture; thiamethoxam