Accumulation of heavy metals in rice and the microbial response in a contaminated paddy field

PurposeMicroorganisms play an important role in soil chemical cycling and ecological persistence. However, the effects and mechanisms of microorganisms on the accumulation of heavy metals in soils and rice grains are still unclear. The objective of this study was to determine the correlation between heavy metals and microbial community, and found out the dominant microorganism that influenced the process of heavy metal accumulation in rice grains.Materials and methodsSoil and rice samples were collected from a paddy field near a Pb-Zn mine. High-throughput sequencing technology was applied to investigate the microbial communities in heavy metal contaminated soils, and the interaction between microorganisms and environment variables were analyzed.Results and discussionThe main pollutants of the farmland were Zn, As, Cd, Sb, and Pb in soil and Cd in rice grains. Bacterial and fungal diversity decreased under the stress of heavy metals, and their composition was shaped depending on the contamination level. The bacteria Chlorofexales, Gemmatimonadales, Myxococcales, Solibacterales, and Subgroup_7, fungi Agaricales, Diaporthales, and norank_c__Sordariomycete had strong tolerance to heavy metals. Among these microorganisms, Chlorofexales, Gemmatimonadales, Myxococcales, Solibacterales, and Subgroup_7 might decrease the accumulation of As and Pb in rice grains, while Chlorofexales might decrease the rice Sb accumulation. Furthermore, Agaricales, Diaporthales, and norank_c__Sordariomycetes may decrease the accumulation of As, Pb, and Zn in rice grain.ConclusionThe farmland was heavily polluted by heavy metals, which brings great risks to rice safety and microecological health. And some of microbial taxa was found in soil, which can tolerate and adapt to the stress of heavy metal pollution, even potentially reduce the accumulation of heavy metals in rice grains.