Dehalococcoides and general bacterial ecology of differentially trichloroethene dechlorinating flow-through columns

Mirza, Babur S.; Sorensen, Darwin L.; McGlinn, Daniel J.; Dupont, R. Ryan; McLean, Joan E.

doi:10.1007/s00253-017-8180-1

Cited by 9 publications

(4 citation statements)

References 80 publications

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“…There was no significant difference in leaching of As with pulse feeding of either emulsified oil formulations, 18.2 ± 7.36% (EO) to 23.5 ± 4.34% (emulsified oil with nonionic surfactant, EON). It is interesting to note that the addition of whey led to the development of an ecology supportive of dechlorinating bacteria (Mirza et al ) and full dechlorination of TCE to nonchlorinated products including ethene and methane (McLean et al ). The emulsified oil produced only partial dechlorination (McLean et al ), with less As leaching compared with the whey treatment (Figure ).…”

Section: Resultsmentioning

confidence: 99%

Arsenic Release and Attenuation Processes in a Groundwater Aquifer During Anaerobic Remediation of TCE with Biostimulation

Smith¹,

Dupont²,

McLean³

2019

Groundwater Monitoring Rem

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Arsenic in groundwater in excess of the drinking water limit is usually from natural sources. The release of As, however, can be amplified by anthropogenic inputs of carbon, including those associated with the remediation of chlorinated solvents such as trichloroethylene (TCE). Large laboratory columns (15.2 cm diameter, 183 cm long) packed with aquifer solids from a TCE contaminated site near Hill Air Force Base (Utah) were fed with groundwater containing TCE and were biostimulated, bioaugmented, and monitored for TCE dechlorination over 7.5 years. This is a basin‐fill aquifer with As bearing geologic features. The objective of this study was to evaluate the biogeochemical changes that affect As solubilization that occurred after 7.5 years of feeding the columns with either whey or two formulations of Newman Zone® emulsified oil, and a no carbon addition control. The columns were analyzed in 10.16 cm sections for pore water and sediment quality parameters, parameters descriptive of redox conditions, and As geochemistry. The whey treatment resulted in 52.9% (±1.36%) (average ± standard deviation) of the total As in the solids leaching from the columns. The oil treatments promoted loss of 20.9% (±6.40%) of the total As. Arsenic solubility was associated with strongly reducing conditions developed with whey addition, leading to dissolution of crystalline Fe oxides and release of As. Arsenic was attenuated within the oil treated columns with As associated with carbonates in the lower layers. A consequence of adding whey, resulting in the desired full dechlorination of TCE in this aquifer, is the mobilization of As in groundwater.

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Section: Resultsmentioning

confidence: 99%

Arsenic Release and Attenuation Processes in a Groundwater Aquifer During Anaerobic Remediation of TCE with Biostimulation

Smith¹,

Dupont²,

McLean³

2019

Groundwater Monitoring Rem

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“…Consequently, extra attention might be needed in stage-II to minimize unexpected overgrowth of other microorganisms, particularly the proper time and inoculation ratio of culture transfers. In previous studies, many biostimulation and bioaugmentation strategies (i.e., addition of carbon source, electron donor, and functional microorganisms) were employed to enrich OHRB, but their relative abundance was generally lower than 30% or fluctuated in the range of 30–60%. ,,− The fastidious and slow-growing OHRB were easily suppressed by their competitors. , The further enrichment of OHRB was governed by different stochastic processes, emphasizing the importance of monitoring OHRB and successional patterns of their microbial communities to minimize the stochastic variance.…”

Section: Discussionmentioning

confidence: 99%

Organohalide-Respiring Bacteria in Polluted Urban Rivers Employ Novel Bifunctional Reductive Dehalogenases to Dechlorinate Polychlorinated Biphenyls and Tetrachloroethene

Qiu

Fang

et al. 2020

Environ. Sci. Technol.

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Polluted urban river sediments could be a sink of persistent and toxic polychlorinated biphenyls (PCBs) in urban areas and provide desired growth niches for organohalide-respiring bacteria (OHRB). In this study, microcosms were set up with surface sediments of nationwide polluted urban rivers in China, of which 164 cultures could dechlorinate tetrachloroethene (PCE) to dichloroethenes (DCEs) and to vinyl chloride and/or ethene. Further in vivo tests showed extensive PCB dechlorination with different pathways in 135 PCE pregrown cultures. Taking reductive dechlorination of PCB180 (2345-245-CB) as an example, 121 and 14 cultures preferentially removed flanked para-and meta-chlorines, respectively. Strikingly, all in vitro assays with the 135 PCE pregrown cultures showed identical PCB dechlorination pathways with their living cultures, implying the involvement of bifunctional reductive dehalogenases (RDases) to dechlorinate both PCBs and PCE. Further 16S rRNA and RDase gene-based analyses, together with enantioselective dechlorination of chiral PCBs, suggested that Dehalococcoides and Dehalogenimonas in the 135 cultures largely employed distinctively different novel bifunctional RDases to catalyze PCB/PCE dechlorination. Quantitative assessment of the community assembly process with the modified stochasticity ratio (MST) indicated three different stages in enrichment of OHRB. The second stage, as the only one controlled by stochastic processes (MST > 0.5), required extra attention in monitoring community successional patterns to minimize stochastic variance for enriching the PCB/PCEdechlorinating OHRB.

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“…Paired-end Illumina reads were assembled to generate consensus sequences, and initial quality filtration was done using mothur software (70). Initial quality filtrations such as min-length = 370, max-ambig = 3, max-homp = 8, etc., were performed as described previously (71). Chimeric DNA sequences were identified and removed using the Ribosomal Database Project (RDP) platform.…”

Section: Methodsmentioning

confidence: 99%

Soybean Root Nodule and Rhizosphere Microbiome: Distribution of Rhizobial and Nonrhizobial Endophytes

Mayhood

Mirza

2021

Appl Environ Microbiol

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Soybean root nodules are known to contain a high diversity of both rhizobial and non-rhizobial endophytes (NREs). Nevertheless, the variation of these bacteria among different root nodules within single plants has not been reported. So far, it is unclear whether the selection of NREs among different root nodules within single plants is a random process or is strictly controlled by the host plant toward a few specific NREs based on their beneficial influence on plant growth. Secondly, it is also unknown if the relative frequency of NREs within different root nodules is consistent or it varies based on the location or size of a root nodule. We assessed the microbiomes of 193 individual soybean root nodules from nine plants using high-throughput DNA sequencing. Bradyrhizobium japonicum strains occurred in high abundance in all root nodules despite the presence of other soybean-compatible rhizobia such as Ensifer, Mesorhizobium, and other species of genus Bradyrhizobium in soil. Nitrobacter and Tardiphaga were the two non-rhizobial genera that were uniformly detected within almost all root nodules, though they were in low abundance. DNA sequences related to previously frequently reported other NREs such as Bacillus, Pseudomonas, Flavobacterium, and Variovorax species were detected within a few nodules. Unlike Bradyrhizobium, the low abundance and inconsistent occurrence of previously reported NREs among different root nodules within single plants suggest that these microbes are not being preferentially selected as endophytes by host plants, and most likely play a limited part in plant growth as endophytes. IMPORTANCE Soybean (Glycine max L.) is a valuable food crop that also contributes significantly toward soil nitrogen by developing a symbiotic association with nitrogen-fixing rhizobia. Bacterial endophytes (both rhizobial and non-rhizobial) are considered to be critical for the growth and resilience of the legume host. In the past, several studies have suggested that the selection of bacterial endophytes within root nodules can be influenced by factors, such as soil pH, nutrient availability, host plant genotype, and bacterial diversity in soil. However, the influence of size or location of root nodules on the selection of bacterial endophytes within soybean root is unknown. It is also unclear whether the selection of non-rhizobial endophytes within different root nodules of a single plant is a random process or is strictly regulated by the host. This information can be useful in identifying potential bacterial species for developing bioinoculants that can enhance plant growth and soil nitrogen.

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Dehalococcoides and general bacterial ecology of differentially trichloroethene dechlorinating flow-through columns

Cited by 9 publications

References 80 publications

Arsenic Release and Attenuation Processes in a Groundwater Aquifer During Anaerobic Remediation of TCE with Biostimulation

Arsenic Release and Attenuation Processes in a Groundwater Aquifer During Anaerobic Remediation of TCE with Biostimulation

Organohalide-Respiring Bacteria in Polluted Urban Rivers Employ Novel Bifunctional Reductive Dehalogenases to Dechlorinate Polychlorinated Biphenyls and Tetrachloroethene

Soybean Root Nodule and Rhizosphere Microbiome: Distribution of Rhizobial and Nonrhizobial Endophytes

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