Microbial Community Responses to Organophosphate Substrate Additions in Contaminated Subsurface Sediments

Abstract

BackgroundRadionuclide- and heavy metal-contaminated subsurface sediments remain a legacy of Cold War nuclear weapons research and recent nuclear power plant failures. Within such contaminated sediments, remediation activities are necessary to mitigate groundwater contamination. A promising approach makes use of extant microbial communities capable of hydrolyzing organophosphate substrates to promote mineralization of soluble contaminants within deep subsurface environments.Methodology/Principal FindingsUranium-contaminated sediments from the U.S. Department of Energy Oak Ridge Field Research Center (ORFRC) Area 2 site were used in slurry experiments to identify microbial communities involved in hydrolysis of 10 mM organophosphate amendments [i.e., glycerol-2-phosphate (G2P) or glycerol-3-phosphate (G3P)] in synthetic groundwater at pH 5.5 and pH 6.8. Following 36 day (G2P) and 20 day (G3P) amended treatments, maximum phosphate (PO4 3−) concentrations of 4.8 mM and 8.9 mM were measured, respectively. Use of the PhyloChip 16S rRNA microarray identified 2,120 archaeal and bacterial taxa representing 46 phyla, 66 classes, 110 orders, and 186 families among all treatments. Measures of archaeal and bacterial richness were lowest under G2P (pH 5.5) treatments and greatest with G3P (pH 6.8) treatments. Members of the phyla Crenarchaeota, Euryarchaeota, Bacteroidetes, and Proteobacteria demonstrated the greatest enrichment in response to organophosphate amendments and the OTUs that increased in relative abundance by 2-fold or greater accounted for 9%–50% and 3%–17% of total detected Archaea and Bacteria, respectively.Conclusions/SignificanceThis work provided a characterization of the distinct ORFRC subsurface microbial communities that contributed to increased concentrations of extracellular phosphate via hydrolysis of organophosphate substrate amendments. Within subsurface environments that are not ideal for reductive precipitation of uranium, strategies that harness microbial phosphate metabolism to promote uranium phosphate precipitation could offer an alternative approach for in situ sequestration.

Arbuscular Mycorrhizal Fungi Alleviate the Negative Effects of Iron Oxide Nanoparticles on Bacterial Community in Rhizospheric Soils

“…Moreover, Yamada and Sekiguchi (2009) report that Anaerolineae can decompose carbohydrates, especially relatively recalcitrant carbon compounds; therefore, an increase in Anaerolineae would positively influence carbon cycling and promote nutrient release from organic compounds in soils. Similarly, Cao et al (2015) reported that AMF increase the abundance of Flavobacteriaceae, subsequently enhancing the availability and utilization of phosphorus in soils (Martinez et al, 2014). Therefore, it should be emphasized that AMF have positive effects not only on plants but also on soil microorganisms and soil function under ENP treatments.…”

Interactive impacts of earthworms (Eisenia fetida) and arbuscular mycorrhizal fungi (Funneliformis mosseae) on the bioavailability of calcium phosphates

“…CK is the soil without earthworm and AM fungi addition; E is the soil with earthworm addition; AM is soil with AM fungi addition; E+AM is the soil with both earthworm and AM fungi addition Data are the means of four replicates±STD and were compared by Duncan's multiple range tests. Within each column (4 values) the values with the same lower case letter are not significantly different CK is the soil without earthworm and AM fungi addition; E is the soil with earthworm addition; AM is soil with AM fungi addition; E+AM is the soil with both earthworm and AM fungi addition AM hyphal Contribution to plant P uptake (%)=(Total P uptake by AM plants-total P uptake by non-AM plants)/Total P uptake by AM plants×100 % (Feng et al, 2003) Utilization efficiency of Ca-P by plants (%) = Total P uptake (mg)/ Total addition Ca-P (50 mg) 2014; Martinez et al 2014), and some of them have been noted as plant growth-promoting rhizobacteria (PGPR) in numerous review articles. Therefore, we think that the effect of earthworms on calcium phosphate bioavailability may be related to 1) production of organic acids by gut microbes and the soil pH decrease, and/or 2) an influence on soil bacterial abundance and increased abundance of Flavobacteriaceae.…”

“…Earthworm-increased microbial biomass P may be due to the production of organic acids by their gut microbes, which could impact the acid phosphatase biosynthesis in the primary P solubilization of microorganisms (Arcand and Schneider 2006). AM hyphae released exudates, which included organic acids and/or express phosphatase enzymes (e.g., acid/alkaline phosphohydrolases), to regulate the microbial biomass P by stimulating soil microbial activities (Martinez et al 2014). The impact of the interaction between earthworms and AM fungi on the production of organic acids is likely important in microbial turnover during P cycling.…”

Phosphate-Mediated Remediation of Metals and Radionuclides

“…New and emerging methods, such as metagenomics and metaproteomics, which allow for a greater understanding of microbe-metal interactions, many of which were pioneered as a result of academic and U.S. Department of Energy National Laboratory collaborations, have yielded significant insights into subsurface microbial community dynamics and physiological responses within contaminated environments [194][195][196][197][198][199][200][201][202][203][204][205][206]. Additionally, synchrotron X-ray techniques (e.g., XRD, XANES, and EXAFS) have become tools for biogeochemical studies that enhance our understanding of in situ contaminant sequestration.…”