Long-Term Manure Application Changes Bacterial Communities in Rice Rhizosphere and Arsenic Speciation in Rice Grains

Abstract

Bioavailability and speciation of arsenic (As) are impacted by fertilization and bacteria in the rice rhizosphere. In this study, we investigated the effects of long-term manure application on As bioavailability, microbial community structure, and functional genes in a rice paddy field. The results showed that manure application did not affect total As in the soil but increased soluble As forms by 19%, increasing arsenite (As­(III)) accumulation in rice grains and roots by 34 and 64% compared to a control. A real-time quantitative polymerase chain reaction (qPCR) and high-throughput sequencing analysis demonstrated that manure application increased the relative abundance of Rhizobium, Burkholderia, Sphingobium, and Sphingomonas containing arsenate reductase genes (arsC) in the rhizosphere soil, consistent with the 529% increase in arsC, which may have promoted arsenate (As­(V)) reduction and increased As availability in pore water. In addition, manure application significantly altered the iron (Fe)-plaque microbial community structure and diversity. The microbes, particularly, Bradyrhizobium, Burkholderia, and Ralstonia, were mostly associated with As, Fe, and sulfur (S) cycles. This result was consistent with changes in the functional genes related to As, Fe, and S transformation. Although manure application promoted As­(V) reduction (arsC) in Fe-plaque by 682%, it inhibited Fe and S reduction by decreasing FeIII reduction bacteria (Geobacteraceae) and the sulfate-reducing gene (dsrA) abundance. Further, manure application changed the composition of the microbial community that contained the arsC gene. In short, caution needs to be excised even in the soil with a low As concentration as manure application increased As­(III) accumulation in rice grains.

Organic mulch can suppress litchi downy blight through modification of soil microbial community structure and functional potentials

“…Soil microbiota are closely related to soil quality and ecosystem stability and sustainability, which are crucial for plant health and productivity [ 31 ]. Various studies demonstrated the alteration of soil microbial community was closely associated with soil suppressiveness to soilborne pathogenic fungi [ 32 , 33 ].…”

Effects and Mechanisms of Copper Oxide Nanoparticles with Regard to Arsenic Availability in Soil–Rice Systems: Adsorption Behavior and Microbial Response

“…The increase in Fe­(III)-reducing and sulfur-reducing bacteria increased As mobilization in soil; the effects of CuO NPs on the microbial community and redox microorganisms on As-contaminated soil need to be further evaluated. The rhizosphere is the most active region in soil, and the oxygen released from root aerenchyma could oxidize As­(III) and Fe­(II), which promotes the formation of Fe plaques and hinders the uptake of As by rice roots. , Fe plaques are mainly formed at the tillering stage of rice growth; iron-oxidizing bacteria play an important role in Fe­(II) oxidation and Fe plaque formation, whereas the activity of Fe­(III)-reducing bacteria contribute to the decomposition of Fe plaques by Fe­(III) dissimilatory reduction. , Meanwhile, the abundance of As­(V)-reducing ( arsC ) and sulfate-reducing ( dsrA ) genes in Fe plaques have a significant effect on As­(III) accumulation in rice grains . Hence, the increase in Fe­(III)-reducing and sulfur-reducing bacteria would promote the As bioavailability in soil.…”

Organic Mulching can Suppress Litchi Downy Blight Through Modification of Soil Microbial Community Structure and Functional Potentials

“…The structure and functions of soil microbial community are closely related to soil quality and ecosystem stability and sustainability, which are crucial for plant health and productivity [22]. Various studies demonstrated the alteration of soil microbial community was closely associated with soil suppressiveness to soilborne pathogenic fungi [23,24].…”