Characterization of zn mobilizing microbes in arsenic rich rice soils and their potential application

Abstract

Zinc (Zn) deficiency and arsenic (As) accumulation in rice plant increase the risk of malnutrition newlineand health hazards, respectively which warrants mitigation of As translocation but enhance newlineacquisition of Zn in rice plant. Here, the role Zn-solubilizing bacteria (ZSB) and bacterially newlinesolubilized Zn (BSZn) obtained from their culture has been researched for the above purpose. newlineEight (EIKU12, EIKU13, EIKU14, EIKU15, EIKU16, EIKU17, EIKU18 and EIKU19) newlineheterotrophic bacteria were isolated from As rich rice rhizosphere using nitrogen-free medium newlineand were found to solubilize inorganic Zn salt(s) efficiently. 16S rRNA gene analysis revealed newlineout of eight, five were affiliated with Burkholderia spp. (EIKU12-EIKU17) and the rest with newlineAchromobacter spp. (EIKU18) and Pseudomonas sp. (EIKU19). Burkholderia spp. tolerated newlinemore amount of Zn compared to other. All the isolates tolerated more than 1 mM As(III) while newlinePseudomonas sp. registered 12 mM. Conversely, all the Burkholderia spp. and Achromobacter newlinesp. tolerated more than 50 mM As(V) compared to Pseudomonas sp. (26 mM). Most of the newlineisolates showed P- and K-solubilization and IAA production ability. Zinc solubilizing efficiency newline(ZSE) of the bacteria varied with the concentrations and types of Zn salts used in the experiments. newlineZSE decreased in presence of As(V) in particular. Enriched concentrated cells of the ZSB in newlineglucose amended medium with 0.5% ZnO showed an increasing trend of Zn-solubilization with newlinetime and were able to solubilize more than 300 mg/L Zn. This increased rate of Zn release was newlineattributed to marked decline in pH that might be due to the enhanced gluconic acid production newlinefrom glucose. newline