Effect of arsenic on tolerance mechanisms of two plant growth promoting bacteria used as biological inoculants

ANA L. ARMENDARIZ, MELINA A. TALANO, ANA L. WEVAR OLLER, MARÍA I. MEDINA, ELIZABETH AGOSTINI

JOURNAL OF ENVIRONMENTAL SCIENCES-CHINA

SCIENCE PRESS

Lugar: Marrickville NSW; Año: 2015 vol. 33 p. 203 - 210

1001-0742

Abstract Background and aims Bacterial ability to colonize the rhizosphere of plants in arsenic contaminated soils is greatly important to symbiotic and free-living plant growth-promoting rhizobacteria (PGPR) used as inoculants. The aim of this work was to study the effect of arsenic on root colonization potential of two strains used as soybean inoculants (Bradyrhizobium japonicum E109 and Azospirillum brasilense Az39). Methods Growth under different arsenic concentrations, exopolysaccharides (EPS) and biofilm production, and motility were studied using conventional microbiological methods. The metabolism of arsenate (As5+) and arsenite (As3+), their removal and accumulation were evaluated by graphite furnace atomic absorption spectrophotometry (GF-AAS). Results As3+ inhibited B. japonicum E109 and A. brasilense Az39 growth from 10 µM and 500 µM, respectively. EPS and biofilm production increased significantly under 25 µM As3+ for both strains. Moreover, this was more notorious for Azospirillum under 500 µM As3+, where motility was seriously affected. Both bacterial strains showed similar ability to reduce As5+, while Azospirillum was able to oxidize more As3+ (around 53%) than Bradyrhizobium (17%). In addition, both strains accumulated arsenic in cell biomass. Conclusion Azospirillum brasilense Az39 would be able to more efficiently survive and colonize arsenic contam