Arsenite-oxidizing bacteria exhibiting plant growth promoting traits isolated from the rhizosphere of Oryza sativa L.: Implications for mitigation of arsenic contamination in paddies

• Published in: Journal of hazardous materials 2016-01, Vol.302, p.10-18
• Main Authors: Das, Suvendu, Jean, Jiin-Shuh, Chou, Mon-Lin, Rathod, Jagat, Liu, Chia-Chuan
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Arsenite oxidase gene; Arsenite oxidation; Arsenite oxidation kinetics; Arsenites - metabolism; Bacillus; Bacillus - genetics; Bacillus - isolation & purification; Bacillus - metabolism; Biodegradation, Environmental; Genes, Bacterial; Kinetics; Molecular Sequence Data; Oryza - growth & development; Oryza - microbiology; Oryza sativa; Oxidoreductases - genetics; Oxidoreductases - metabolism; Paddy soil; Plant growth promotion; Plant Roots - growth & development; Plant Roots - microbiology
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2015.09.044

•As(III)-oxidizing bacteria possessing plant growth promoting (PGP) traits isolated.•The strain produced siderophores, IAA, ACC deaminase and solubilized phosphate.•Arenite-oxidase (aoxB) gene of the strain was identified.•Based on 16S rRNA the strain was identified as Bacillus flexus.•Bacterial inoculation significantly decreased As uptake and increased growth of rice in As-contaminated soil Arsenite-oxidizing bacteria exhibiting plant growth promoting (PGP) traits can have the advantages of reducing As-uptake by rice and promoting plant growth in As-stressed soil. A gram-positive bacterium Bacillus flexus ASO-6 resistant to high levels of As (32 and 280mM for arsenite and arsenate, respectively) and exhibiting elevated rates of As(III) oxidation (Vmax=1.34μMmin−110−7 cell) was isolated from rhizosphere of rice. The presence of aoxB gene and exhibition of As(III)-oxidase enzyme activity of this strain was observed. The ability of the strain to produce siderophore, IAA, ACC-deaminase and to solubilize phosphate was verified. The rice seed treated with the strain exhibited significantly improved seed germination and seedling vigor compared with the un-inoculated seeds. The bacterial inoculation significantly increased root biomass, straw yield, grain yield, chlorophyll and carotenoid in the rice plant. Moreover, As uptake from root to shoot and As accumulation in straw and grain decreased significantly as a result of the bacterial inoculation. Noteworthy, the inoculation effect is more prominent in non-flooded soil than it is in flooded soil. Owing to its wide action spectrum, this As(III)-oxidizing PGPB could serve as a potential bio-inoculant for mitigation of As in paddies and sustainable rice production in As-contaminated areas.