Acrylamide biodegradation ability and plant growth-promoting properties of Variovorax boronicumulans CGMCC 4969
Species of the genus Variovorax are often isolated from nitrile or amide-containing organic compound-contaminated soil. However, there have been few biological characterizations of Variovorax and their contaminant-degrading enzymes. Previously, we reported a new soil isolate, Variovorax boronicumulans CGMCC 4969, and its nitrile hydratase that transforms the neonicotinoid insecticide thiacloprid into an amide metabolite. In this study, we showed that CGMCC 4969 is able to degrade acrylamide, a neurotoxicant and carcinogen in animals, during cell growth in a mineral salt medium as well as in its resting state. Resting cells rapidly hydrolyzed 600 mg/L acrylamide to acrylic acid with a half-life of 2.5 min. In in vitro tests, CGMCC 4969 showed plant growth-promoting properties; it produced a siderophore, ammonia, hydrogen cyanide, and the phytohormone salicylic acid. Interestingly, in soil inoculated with this strain, 200 mg/L acrylamide was completely degraded in 4 days. Gene cloning and overexpression in the Escherichia coli strain Rosetta (DE3) pLysS resulted in the production of an aliphatic amidase of 345 amino acids that hydrolyzed acrylamide into acrylic acid. The amidase contained a conserved catalytic triad, Glu59, Lys 134, and Cys166, and an “MRHGDISSS” amino acid sequence at the N-terminal region. Variovorax boronicumulans CGMCC 4969, which is able to use acrylamide for cell growth and rapidly degrade acrylamide in soil, shows promising plant growth-promoting properties. As such, it has the potential to be developed into an effective Bioaugmentation strategy to promote growth of field crops in acrylamide-contaminated soil.
KeywordsAcrylamide Amidase Biodegradation Plant-growth-promoting rhizobacteria Variovoraxboronicumulans
This research was financed by the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions, the Professional and Public Project of National Environmental Protection (201009033), and NSFC for Talents Training in Basic Science (J1103507).
- Bakthavatchalu S, Shivakumar B, Sullia SB (2012) Identification of multi-trait PGPR isolates and evaluation of their potential as biocontrol agents. Acta Biol Indica 1(1):31–37Google Scholar
- Bers K, Leroy B, Breugelmans P, Albers P, Lavigne R, Sorensen SR, Aamand J, De Mot R, Wattiez R, Springael D (2011a) A novel hydrolase identified by genomic-proteomic analysis of phenylurea herbicide mineralization by Variovorax sp. strain SRS16. Appl Environ Microbiol 77:8754–8764PubMedCrossRefGoogle Scholar
- Bers K, Sniegowski K, Albers P, Breugelmans P, Hendrickx L, De Mot R, Springael D (2011b) A molecular toolbox to estimate the number and diversity of Variovorax in the environment: application in soils treated with the phenylurea herbicide linuron. FEMS Microbiol Ecol 76:14–25PubMedCrossRefGoogle Scholar
- Han JI, Choi HK, Lee SW, Orwin PM, Kim J, Laroe SL, Kim TG, O’Neil J, Leadbetter JR, Lee SY, Hur CG, Spain JC, Ovchinnikova G, Goodwin L, Han C (2011) Complete genome sequence of the metabolically versatile plant growth-promoting endophyte Variovorax paradoxus S110. J Bacteriol 193:1183–1190PubMedCrossRefGoogle Scholar
- Pace H, Brenner C (2001) The nitrilase superfamily: classification, structure and function. Genome Biol 2:REVIEWS0001Google Scholar
- Reeves MW, Pine L, Neilands JB, Balows A (1983) Absence of siderophore activity in Legionella species grown in iron-deficient media. J Bacterial 154:324–329Google Scholar
- Syed MA, Ahmad SA, Kusnin N, Shukor MYA (2012) Purification and characterization of amidase from acrylamide-degrading bacterium Burkholderia sp. strain DR.Y27. Afr J Biotechnol 11:329–336Google Scholar
- Zhang HJ, Zhou QW, Zhou GC, Cao YM, Dai YJ, Ji WW, Shang GD, Yuan S (2012) Biotransformation of the neonicotinoid insecticide thiacloprid by the bacterium Variovorax boronicumulans strain J1 and mediation of the major metabolic pathway by nitrile hydratase. J Agric Food Chem 60:153–159PubMedCrossRefGoogle Scholar