Biotransformation of the Neonicotinoid Insecticide Thiacloprid by the Bacterium Variovorax boronicumulans Strain J1 and Mediation of the Major Metabolic Pathway by Nitrile Hydratase

Abstract

A neonicotinoid insecticide thiacloprid-degrading bacterium strain J1 was isolated from soil and identified as Variovorax boronicumulans by 16S rRNA gene sequence analysis. Liquid chromatography-mass spectrometry and nuclear magnetic resonance analysis indicated the major pathway of thiacloprid (THI) metabolism by V. boronicumulans J1 involved hydrolysis of the N-cyanoimino group to form an N-carbamoylinino group containing metabolite, THI amide. Resting cells of V. boronicumulans J1 degraded 62.5% of the thiacloprid at a concentration of 200 mg/L in 60 h, and 98% of the reduced thiacloprid was converted to the final metabolite thiacloprid amide. A 2.6 kb gene cluster from V. boronicumulans J1 that includes the full length of the nitrile hydratase gene was cloned and investigated by degenerate primer polymerase chain reaction (PCR) and inverse PCR. The nitrile hydratase gene has a length of 1304 bp and codes a cobalt-type nitrile hydratase with an α-subunit of 213 amino acids and a β-subunit of 221 amino acids. The nitrile hydratase gene was recombined into plasmid pET28a and overexpressed in Escherichia coli BL21 (DE3). The resting cells of recombinant E. coli BL21 (DE3)-pET28a-NHase with overexpression of nitrile hydratase transformed thiacloprid to its amide metabolite, whereas resting cells of the control E. coli BL21 (DE3)-pET28a did not. Therefore, the major hydration pathway of thiacloprid is mediated by nitrile hydratase.

The Plant Growth-Promoting Rhizobacterium Variovorax boronicumulans CGMCC 4969 Regulates the Level of Indole-3-Acetic Acid Synthesized from Indole-3-Acetonitrile

“…The molar transformation rate (the total amounts of IAM and IAA divided by the consumed amount of IAN) at 72 h was 86.6%, which indicated that the synthesis of IAM and IAA was the main pathway of IAN metabolism in strain CGMCC 4969. CGMCC 4969 NHase is a cobalt-dependent metalloenzyme, and adding cobalt ions apparently enhanced its activity (15,16). As Fig.…”

“…They are also common plant symbionts found in the rhizosphere and used as model bacteria for the study of microbe-plant interactions (13,14). We previously isolated Variovorax boronicumulans strain CGMCC 4969, which can degrade the neonicotinoid insecticides thiacloprid and acetamiprid to their corresponding amide metabolites (15,16). V. boronicumulans CGMCC 4969 showed some plant growth-promoting traits, such as producing exopolymer substances, siderophores, ammonia, and hydrogen cyanide and secreting salicylate and 2, 3-dihydroxy benzoic acid (17).…”

Isolation and characterization of soil bacteria able to rapidly degrade the organophosphorus nematicide fosthiazate

“…Variovorax have been associated with the degradation of phenylurea herbicides (Dejonghe et al 2003;Bers et al 2011). Regarding V. boronicumulans, strains belonging to this species have been reported as degraders of acrylamide (Liu et al 2013) and of the neonicotinoid insecticide thiacloprid (Zhang et al 2012). Overall, our enrichment cultures resulted in the isolation of the first fosthiazate-degrading bacterium identified as Variovorax boronicumulans.…”

“…) and of the neonicotinoid insecticide thiacloprid (Zhang et al . ). Overall, our enrichment cultures resulted in the isolation of the first fosthiazate‐degrading bacterium identified as Variovorax boronicumulans .…”

Nitrile-Degrading Bacteria Isolated from Compost

“…Sequencing and assembly of 3,471,160 paired-end reads resulted in a draft genome of 7.14 Mbp (131-fold coverage). Although V. boronicumulans is a species described just recently (Miwa et al, 2008), evidence for nitrile degradation by this microorganism was reported before (Zhang et al, 2012;Liu et al, 2013). A search for genes encoding putative nitriledegrading enzymes resulted in the identification of genes for two possible degradation pathways, the first one via a nitrilase (BKP43_17560) and the second one via an NHase (BKP43_58000 and BKP43_58010) and amidase (BKP43_28100).…”