Variovorax CGMCC 4969 And Its Plant Growth-promoting Properties Of Acrylamide Degradation

The species of genus Variovorax are often isolated from nitrile or amide containing organic compound contaminated soil. However the biological characterizations of Variovorax and the contaminant degrading enzymes have been poorly studied. We previously reported a newly soil isolate Variovorax boronicumulans CGMCC4969and its nitrile hydratase transformed neonicotinoid insecticide thiacloprid to amide metabolite. In the present study, we report V. boronicumulans CGMCC4969utilized the worldwide-used acrylamide, a neurotoxicant and carcinogen in animals, for cell growth in mineral salt medium and the resting cells rapidly hydrolyze600mg/L of acrylamide to acrylic acid with a half-life of2.5min. Interestingly, the soil with inoculum of PGPR V. boronicumulans CGMCC4969thoroughly degraded200mg/L acrylamide by100%in4d.V. boronicumulans CGMCC4969is a plant-growth-promoting rhizobacterium(PGPR) with releasing siderophores, ammonia, hydrogen cyanide and phytohormone salicylic acid, but it does not secrete indole acetic acid, and it without the ability of phosphate solubilization.V. boronicumulans CGMCC4969was cloned and inversted by the conserved sequences and inverse PCR. We find that the sequence of the amidase include1038bp and blast-analysis showed that the genes belonging to the aliphatic amidase. The aliphatic amidase with length of345amino acids is responsible for hydrolysis of acrylamide to acrylic acid. The target amidase has a conserved catalytic triad, Glu59, Lys134and Cys166, and contains a special amino acid sequence’RGAELIIRCQG’ in central region. The sequence was overexpressed in E.coli Rosseta (DE3) pLysS. The host bactiera can hydrolyze acrylamide to acrylic acid, and the half-time of degradation is75min. The promising PGPR V. boronicumulans CGMCC4969, which is able to utilize acrylamide for cell growth and rapidly degrade acrylamide in soil, can be developed as a bioaugumentation to promote growth of field crops in acrylamide contaminated soil.