Alleviation of cadmium stress in thai rice cultivar (PSL2) by inoculation of indigenous cadmium-resistant microbial consortia

Abstract

© 2019, ALÖKI Kft., Budapest, Hungary. This study was aimed at isolating indigenous soil bacteria exhibiting cadmium (Cd)-resistance, and characterizing their ability to improve growth and reduce Cd bioaccumulation of Thai rice (Oryza sativa L.) PSL2 seedlings. Repeated enrichment, microorganisms were selectively propagated from agricultural soils receiving dredged sediments that contained Cd at 30-50 mg kg-1, in Western Thailand. Over a range of 0-1,000 ppm, the enriched bacterial consortia had a maximum tolerance to Cd at 800 ppm. In batch cultures containing 50 or 100 ppm Cd, they exhibited 53-56 and 69-78% Cd removal, respectively. The inoculation of enriched consortia ameliorated Cd phytotoxicity by promoting rice biomass and growth, and lowering tissue Cd content upon high Cd exposure (50-100 ppm). 16S metagenomic analysis showed that at least the top bacterial phyla of Proteobacteria, Firmicutes, and Bacteroidetes were enriched in the naturally polluted topsoil microorganisms with dominant bacterial phyla including Planctomycetes, Proteobacteria, Acidobacteria, Verrucomicrobia, Bacteroidetes, Chloroflexi, Actinobacteria, Firmicutes, and Gemmatimonadetes. In the enriched consortia, certain predominant detoxifiers (e.g., Acinetobacter sp., Comamonas sp., Enterococcus sp., and Pseudomonas sp.) were explored at a finer taxonomic level among other detected genera. These results emphasized that indigenous soil Cd-resistant microorganisms have potential to cope with metal stress and improve crop plant growth and yield for agricultural benefits.