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Liu C, Chen X, Wang S, Luo Y, Du W, Yin Y, Guo H. A field study of a novel permeable-reactive-biobarrier to remediate chlorinated hydrocarbons contaminated groundwater. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 351:124042. [PMID: 38679128 DOI: 10.1016/j.envpol.2024.124042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 04/22/2024] [Accepted: 04/22/2024] [Indexed: 05/01/2024]
Abstract
Chlorinated hydrocarbons (CHs) pose significant health risks due to their suspected carcinogenicity, necessitating urgent remediation efforts. While the combination of zero-valent iron (Fe0) and microbial action shows promise in mitigating CH contamination, field studies on this approach are scarce. We devised a novel three-layer permeable reactive barrier (PRB) material incorporating Fe0 and coconut shell biochar, effectively implemented at a typical CH-contaminated site. Field monitoring data revealed conducive conditions for reductive dechlorination of CHs, characterized by low oxygen levels and a relatively neutral pH in the groundwater. The engineered PRB material consistently released organic carbon and iron, fostering the proliferation of CH-dechlorinating bacteria. Over a 250-day operational period, the pilot-scale PRB demonstrated remarkable efficacy in CH removal, achieving removal efficiencies ranging from 21.9% to 99.6% for various CH compounds. Initially, CHs were predominantly eliminated through adsorption and iron-mediated reductive dechlorination. However, microbial reductive dechlorination emerged as the predominant mechanism for sustained and long-term CHs removal. These findings underscore the economic viability and effectiveness of our approach in treating CH-contaminated groundwater, offering promising prospects for broader application in environmental remediation efforts.
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Affiliation(s)
- Cuicui Liu
- Jiangsu Province Engineering Research Center of Soil and Groundwater Pollution Prevention and Control, Jiangsu Provincial Key Laboratory of Environmental Engineering, Jiangsu Provincial Academy of Environmental Science, Nanjing, 210036, China; Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing, 210023, China.
| | - Xiaohui Chen
- School of Civil Engineering, University of Leeds, Leeds, LS2 9JT, UK.
| | - Shui Wang
- Jiangsu Province Engineering Research Center of Soil and Groundwater Pollution Prevention and Control, Jiangsu Provincial Key Laboratory of Environmental Engineering, Jiangsu Provincial Academy of Environmental Science, Nanjing, 210036, China.
| | - Yongming Luo
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.
| | - Wenchao Du
- School of the Environment, Nanjing Normal University, Nanjing, 210023, China.
| | - Ying Yin
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing, 210023, China.
| | - Hongyan Guo
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing, 210023, China; Joint International Research Centre for Critical Zone Science-University of Leeds and Nanjing University, Nanjing University, Nanjing, 210023, China.
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2
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The gut microbiome variability of a butterflyfish increases on severely degraded Caribbean reefs. Commun Biol 2022; 5:770. [PMID: 35908086 PMCID: PMC9338936 DOI: 10.1038/s42003-022-03679-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 07/07/2022] [Indexed: 12/25/2022] Open
Abstract
Environmental degradation has the potential to alter key mutualisms that underlie the structure and function of ecological communities. How microbial communities associated with fishes vary across populations and in relation to habitat characteristics remains largely unknown despite their fundamental roles in host nutrition and immunity. We find significant differences in the gut microbiome composition of a facultative coral-feeding butterflyfish (Chaetodon capistratus) across Caribbean reefs that differ markedly in live coral cover (∼0–30%). Fish gut microbiomes were significantly more variable at degraded reefs, a pattern driven by changes in the relative abundance of the most common taxa potentially associated with stress. We also demonstrate that fish gut microbiomes on severely degraded reefs have a lower abundance of Endozoicomonas and a higher diversity of anaerobic fermentative bacteria, which may suggest a less coral dominated diet. The observed shifts in fish gut bacterial communities across the habitat gradient extend to a small set of potentially beneficial host associated bacteria (i.e., the core microbiome) suggesting essential fish-microbiome interactions may be vulnerable to severe coral degradation. The gut microbiome composition of the coral-feeding butterflyfish across Caribbean reefs is more variable at degraded reefs. These microbiomes have a lower abundance of Endozoicomonas and a higher diversity of anaerobic fermentative bacteria.
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Yuan M, Xin J, Wang X, Zhao F, Wang L, Liu M. Coupling microscale zero-valent iron and autotrophic hydrogen-bacteria provides a sustainable remediation solution for trichloroethylene-contaminated groundwater: Mechanisms, regulation, and engineering implications. WATER RESEARCH 2022; 216:118286. [PMID: 35339054 DOI: 10.1016/j.watres.2022.118286] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 03/08/2022] [Accepted: 03/10/2022] [Indexed: 06/14/2023]
Abstract
Coupling microscale zero-valent iron (mZVI) and autotrophic hydrogen bacteria (AHB) has gained increasing attention owing to its potential to improve dechlorination performance by bridging H2 donors and acceptors. However, few studies have attempted to test its sustainable remediation performance and to comprehensively unveil the governing mechanisms. This study systematically compared the performances of different systems (mZVI, H2-AHB, and mZVI-AHB) for trichloroethylene (TCE) removal, and further optimized dechlorination and H2 evolution of mZVI-AHB synchronously by regulating the mZVI particle size and dosage to achieve a win-win remediation solution. The final removal efficiency and removal rate of TCE by mZVI-AHB were 1.67-fold and 5.30-fold of those by mZVI alone respectively, and mZVI-AHB resulted in more complete dechlorination than H2-AHB alone. Combining H2 evolution kinetics, material characterization data, and bacterial community analysis results, the improved dechlorination performance of mZVI-AHB was mainly due to the following mechanisms: H2 generated by mZVI corrosion was efficiently utilized by AHB, lasting corrosion of mZVI was facilitated by AHB, and dechlorination functional bacteria were highly enriched by mZVI. Finally, the remediation performance of mZVI-AHB with different mZVI particle sizes and dosages was evaluated comprehensively in terms of dechlorination reactivity, H2 utilization efficiency and chemical cost, and suggestions for possible engineering applications are provided.
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Affiliation(s)
- Mengjiao Yuan
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education; Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering; College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Jia Xin
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education; Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering; College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China.
| | - Xiaohui Wang
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education; Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering; College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Fang Zhao
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education; Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering; College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Litao Wang
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education; Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering; College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Meng Liu
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education; Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering; College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
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4
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Inglis AM, Head NA, Chowdhury AIA, Nunez Garcia A, Reynolds DA, Hogberg D, Edwards E, Lomheim L, Weber K, Wallace SJ, Austrins LM, Hayman J, Auger M, Sidebottom A, Eimers J, Gerhard JI, O'Carroll DM. Electrokinetically-enhanced emplacement of lactate in a chlorinated solvent contaminated clay site to promote bioremediation. WATER RESEARCH 2021; 201:117305. [PMID: 34119968 DOI: 10.1016/j.watres.2021.117305] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Revised: 04/27/2021] [Accepted: 05/24/2021] [Indexed: 06/12/2023]
Abstract
Bioremediation through the injection of electron donors and bacterial cultures is effective at treating chlorinated solvent contamination. However, it has had limited application in low permeability zones where amendments cannot be delivered successfully. This field-scale study investigated the application of electrokinetics to enhance the delivery of lactate at a clay site contaminated with chlorinated solvents. Groundwater and soil samples were collected before, during and for 1 year after the 71-day field test and analyzed for a wide suite of chemical and biological parameters. Lactate was successfully delivered to all monitoring locations. Lactate emplacement resulted in the stimulation of bacterial populations, specifically within the phylum Firmicutes, which contains fermenters and strict anaerobes. This likely led to biodegradation, as the field trial resulted in significant decreases in both soil and aqueous phase chlorinated solvent concentrations. Contaminant decreases were also partially attributable to dilution, given evidence of some advective lactate flux. This research provides evidence that electrokinetically-enhanced bioremediation has potential as a treatment strategy for contaminated low permeability strata.
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Affiliation(s)
- Ainsley M Inglis
- Department of Civil and Environmental Engineering, University of Western Ontario, 1151 Richmond Rd., London, Ontario, N6A 5B8, Canada
| | - Nicholas A Head
- Department of Civil and Environmental Engineering, University of Western Ontario, 1151 Richmond Rd., London, Ontario, N6A 5B8, Canada
| | - Ahmed I A Chowdhury
- Institute of Water and Flood Management, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
| | - Ariel Nunez Garcia
- Department of Civil and Environmental Engineering, University of Western Ontario, 1151 Richmond Rd., London, Ontario, N6A 5B8, Canada
| | - David A Reynolds
- Geosyntec Consultants, 130 Stone Road W, Guelph, N1G 3Z2, ON, Canada
| | - Dave Hogberg
- Geosyntec Consultants, 130 Stone Road W, Guelph, N1G 3Z2, ON, Canada
| | - Elizabeth Edwards
- University of Toronto, 27 King's College Cir, Toronto, ON M5S 3H7, Canada
| | - Line Lomheim
- University of Toronto, 27 King's College Cir, Toronto, ON M5S 3H7, Canada
| | - Kela Weber
- Royal Military College of Canada, 13 General Crerar Crescent, Kingston, ON K7K 7B4, Canada
| | - Sarah J Wallace
- Royal Military College of Canada, 13 General Crerar Crescent, Kingston, ON K7K 7B4, Canada
| | - Leanne M Austrins
- Dow Chemical, Environmental Remediation and Compliance, Midland, MI, 48674, USA
| | | | - Marlaina Auger
- Geosyntec Consultants, 130 Stone Road W, Guelph, N1G 3Z2, ON, Canada
| | | | - Jake Eimers
- Jacobs, 72 Victoria St S, Kitchener, N2G 4Y9, ON, Canada
| | - Jason I Gerhard
- Department of Civil and Environmental Engineering, University of Western Ontario, 1151 Richmond Rd., London, Ontario, N6A 5B8, Canada
| | - Denis M O'Carroll
- School of Civil and Environmental Engineering, Water Research Centre, University of New South Wales, Sydney, NSW 2052 Australia.
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Lu S, Lu B, Tan G, Moe W, Xu W, Wang Y, Xing D, Zhu X. Mo 2N nanobelt cathodes for efficient hydrogen production in microbial electrolysis cells with shaped biofilm microbiome. Biosens Bioelectron 2020; 167:112491. [PMID: 32798808 DOI: 10.1016/j.bios.2020.112491] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 07/29/2020] [Accepted: 07/31/2020] [Indexed: 10/23/2022]
Abstract
High cost platinum (Pt) catalysts limit the application of microbial electrolysis cells (MECs) for hydrogen (H2) production. Here, inexpensive and efficient Mo2N nanobelt cathodes were prepared using an ethanol method with minimized catalyst and binder loadings. The chronopotentiometry tests demonstrated that the Mo2N nanobelt cathodes had similar catalytic activities for H2 evolution compared to that of Pt/C (10 wt%). The H2 production rates (0.39 vs. 0.37 m3-H2/m3/d), coulombic efficiencies (90% vs. 77%), and overall hydrogen recovery (74% vs. 70%) of MECs with the Mo2N nanobelt cathodes were also comparable to those with Pt/C cathodes. However, the cost of Mo2N nanobelt catalyst ($ 31/m2) was much less than that of Pt/C catalysts ($ 1930/m2). Furthermore, the biofilm microbiomes at electrodes were studied using the PacBio sequencing of full-length 16S rRNA gene. It indicated Stenotrophomonas nitritireducens as a putative electroactive bacterium dominating the anode biofilm microbiomes. The majority of dominant species in the Mo2N and Pt/C cathode communities belonged to Stenotrophomonas nitritireducens, Stenotrophomonas maltophilia, and Comamonas testosterone. The dominant populations in the cathode biofilms were shaped by the cathode materials. This study demonstrated Mo2N nanobelt catalyst as an alternative to Pt catalyst for H2 production in MECs.
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Affiliation(s)
- Sidan Lu
- Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Baiyun Lu
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, China
| | - Guangcai Tan
- Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - William Moe
- Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Wangwang Xu
- Department of Mechanical & Industrial Engineering, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Ying Wang
- Department of Mechanical & Industrial Engineering, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Defeng Xing
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, China
| | - Xiuping Zhu
- Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA, 70803, USA.
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6
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Calcagnile M, Tredici SM, Talà A, Alifano P. Bacterial Semiochemicals and Transkingdom Interactions with Insects and Plants. INSECTS 2019; 10:E441. [PMID: 31817999 PMCID: PMC6955855 DOI: 10.3390/insects10120441] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 12/02/2019] [Accepted: 12/05/2019] [Indexed: 01/08/2023]
Abstract
A peculiar feature of all living beings is their capability to communicate. With the discovery of the quorum sensing phenomenon in bioluminescent bacteria in the late 1960s, it became clear that intraspecies and interspecies communications and social behaviors also occur in simple microorganisms such as bacteria. However, at that time, it was difficult to imagine how such small organisms-invisible to the naked eye-could influence the behavior and wellbeing of the larger, more complex and visible organisms they colonize. Now that we know this information, the challenge is to identify the myriad of bacterial chemical signals and communication networks that regulate the life of what can be defined, in a whole, as a meta-organism. In this review, we described the transkingdom crosstalk between bacteria, insects, and plants from an ecological perspective, providing some paradigmatic examples. Second, we reviewed what is known about the genetic and biochemical bases of the bacterial chemical communication with other organisms and how explore the semiochemical potential of a bacterium can be explored. Finally, we illustrated how bacterial semiochemicals managing the transkingdom communication may be exploited from a biotechnological point of view.
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Affiliation(s)
| | | | | | - Pietro Alifano
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Via Prov.le Lecce-Monteroni, 73100 Lecce, Italy; (M.C.); (S.M.T.); (A.T.)
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7
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Sonthiphand P, Ruangroengkulrith S, Mhuantong W, Charoensawan V, Chotpantarat S, Boonkaewwan S. Metagenomic insights into microbial diversity in a groundwater basin impacted by a variety of anthropogenic activities. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2019; 26:26765-26781. [PMID: 31300992 DOI: 10.1007/s11356-019-05905-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 07/03/2019] [Indexed: 06/10/2023]
Abstract
Microbial communities in groundwater are diverse and each may respond differently to environmental change. The goal of this study was to investigate the diversity, abundance, and dynamics of microbial communities in impacted groundwater and correlate them to the corresponding land use and groundwater geochemistry, using an Illumina MiSeq platform targeting the V3 and V4 regions of the 16S rRNA gene. The resulting MiSeq sequencing revealed the co-occurrence patterns of both abundant and rare microbial taxa within an impacted groundwater basin. Proteobacteria were the most common groundwater-associated bacterial phylum, mainly composed of the classes Gammaproteobacteria, Betaproteobacteria, Alphaproteobacteria, and Deltaproteobacteria. The phyla detected at less abundances were the Firmicutes, Bacteroidetes, Planctomycetes, Actinobacteria, OD1, and Nitrospirae. The members of detected groundwater microorganisms involved in natural biogeochemical processes such as nitrification, anammox, methane oxidation, sulfate reduction, and arsenic transformation. Some of the detected microorganisms were able to perform anaerobic degradation of organic pollutants. The resulting PCA indicates that major land usage within the sampling area seemed to be significantly linked to the groundwater microbial distributions. The distinct microbial pattern was observed in the groundwater collected from a landfill area. This study suggests that the combinations of anthropogenic and natural effects possibly led to a unique pattern of microbial diversity across different locations at the impacted groundwater basin.
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Affiliation(s)
- Prinpida Sonthiphand
- Department of Biology, Faculty of Science, Mahidol University, 272 Rama VI Road, Ratchathewi, Bangkok, 10400, Thailand.
| | - Siwat Ruangroengkulrith
- Department of Biochemistry, Faculty of Science, Mahidol University, 272 Rama VI Road, Ratchathewi, Bangkok, 10400, Thailand
| | - Wuttichai Mhuantong
- Enzyme Technology Laboratory, National Center for Genetic Engineering and Biotechnology, Phahonyothin Road, Khlong Luang, Pathum Thani, 12120, Thailand
| | - Varodom Charoensawan
- Department of Biochemistry, Faculty of Science, Mahidol University, 272 Rama VI Road, Ratchathewi, Bangkok, 10400, Thailand
- Integrative Computational BioScience (ICBS) Center, Mahidol University, Salaya, Phuttamonthon, Nakhon Pathom, Thailand
- Systems Biology of Diseases Research Unit, Faculty of Science, Mahidol University, Salaya, Phuttamonthon, Nakhon Pathom, Thailand
| | - Srilert Chotpantarat
- Department of Geology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
- Research Program on Controls of Hazardous Contaminants in Raw Water Resources for Water Scarcity Resilience, Center of Excellence on Hazardous Substance Management (HSM), Chulalongkorn University, Bangkok, Thailand
- Research Unit of Green Mining (GMM), Chulalongkorn University, Bangkok, Thailand
| | - Satika Boonkaewwan
- Research Program on Controls of Hazardous Contaminants in Raw Water Resources for Water Scarcity Resilience, Center of Excellence on Hazardous Substance Management (HSM), Chulalongkorn University, Bangkok, Thailand
- International Postgraduate Program in Hazardous Substance and Environmental Management, Chulalongkorn University, 9th Floor, CU Research Building, Phayathai Road, Bangkok, 10330, Thailand
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8
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Moe WM, Reynolds SJ, Griffin MA, McReynolds JB. Bioremediation Strategies Aimed at Stimulating Chlorinated Solvent Dehalogenation Can Lead to Microbially-Mediated Toluene Biogenesis. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:9311-9319. [PMID: 30044084 DOI: 10.1021/acs.est.8b02081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In situ bioremediation practices that include subsurface addition of fermentable electron donors to stimulate reductive dechlorination by anaerobic bacteria have become widely employed to combat chlorinated solvent contamination in groundwater. At a contaminated site located near Baton Rouge, Louisiana (USA), toluene was transiently observed in groundwater at concentrations that sometimes far exceeded the US drinking water maximum contaminant level (MCL) of 1 mg/L after a fermentable substrate (agricultural feed grade cane molasses) was injected into the subsurface with the intent of providing electron donors for reductive dechlorination. Here, we present data that demonstrate that indigenous microorganisms can biologically produce toluene by converting phenylacetic acid, phenylalanine, phenyllactate, and phenylpyruvate to toluene. When grown in defined medium with phenylacetic acid at concentrations ≤350 mg/L, the molar ratio between toluene accumulated and phenylacetic acid supplied was highly correlated ( R2 ≥ 0.96) with a toluene yield exceeding 0.9:1. Experiments conducted using 13C labeled compounds (phenylacetic acid-2-13C and l-phenylalanine-3-13C) resulted in production of toluene-α-13C, confirming that toluene was synthesized from these precursors by two independently developed enrichment cultures. Results presented here suggest that monitoring of aromatic hydrocarbons is warranted during enhanced bioremediation activities where electron donors are introduced to stimulate anaerobic biotransformation of chlorinated solvents.
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Affiliation(s)
- William M Moe
- Department of Civil and Environmental Engineering , Louisiana State University , 3255 Patrick F. Taylor Hall , Baton Rouge , Louisiana 70803 , United States
| | - Samuel J Reynolds
- Department of Civil and Environmental Engineering , Louisiana State University , 3255 Patrick F. Taylor Hall , Baton Rouge , Louisiana 70803 , United States
| | - M Aaron Griffin
- Department of Civil and Environmental Engineering , Louisiana State University , 3255 Patrick F. Taylor Hall , Baton Rouge , Louisiana 70803 , United States
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Liang Y, Meggo R, Hu D, Schnoor JL, Mattes TE. Microbial community analysis of switchgrass planted and unplanted soil microcosms displaying PCB dechlorination. Appl Microbiol Biotechnol 2015; 99:6515-26. [PMID: 25820643 DOI: 10.1007/s00253-015-6545-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 03/12/2015] [Accepted: 03/13/2015] [Indexed: 11/28/2022]
Abstract
Polychlorinated biphenyls (PCBs) pose potential risks to human and environmental health because they are carcinogenic, persistent, and bioaccumulative. In this study, we investigated bacterial communities in soil microcosms spiked with PCB 52, 77, and 153. Switchgrass (Panicum virgatum) was employed to improve overall PCB removal, and redox cycling (i.e., sequential periods of flooding followed by periods of no flooding) was performed in an effort to promote PCB dechlorination. Lesser chlorinated PCB transformation products were detected in all microcosms, indicating the occurrence of PCB dechlorination. Terminal restriction fragment length polymorphism (T-RFLP) and clone library analysis showed that PCB spiking, switchgrass planting, and redox cycling affected the microbial community structure. Putative organohalide-respiring Chloroflexi populations, which were not found in unflooded microcosms, were enriched after 2 weeks of flooding in the redox-cycled microcosms. Sequences classified as Geobacter sp. were detected in all microcosms and were most abundant in the switchgrass-planted microcosm spiked with PCB congeners. The presence of possible organohalide-respiring bacteria in these soil microcosms suggests that they play a role in PCB dechlorination therein.
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Affiliation(s)
- Yi Liang
- Department of Civil and Environmental Engineering, 4105 Seamans Center, The University of Iowa, Iowa City, IA, 52242, USA
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Lacroix E, Brovelli A, Maillard J, Rohrbach-Brandt E, Barry DA, Holliger C. Use of silicate minerals for long-term pH control during reductive dechlorination of high tetrachloroethene concentrations in continuous flow-through columns. THE SCIENCE OF THE TOTAL ENVIRONMENT 2014; 482-483:23-35. [PMID: 24636885 DOI: 10.1016/j.scitotenv.2014.02.099] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 02/12/2014] [Accepted: 02/21/2014] [Indexed: 06/03/2023]
Abstract
The long-term buffering potential of three silicate minerals (diopside, fayalite and forsterite) present as fine particles in porous quartz sand medium was evaluated in flow-through column experiments over a period of 6.5 months. The columns were operated with PCE concentrations close to saturation and inoculated with the organohalide-respiring consortium SDC-9™, which is able to completely dechlorinate PCE to ethene at high concentrations. In the absence of pH buffering agents, fermentation and organohalide respiration drove the pH close to 6.1, leading to severe inhibition of PCE dechlorination. Forsterite and fayalite were able to maintain the pH close to 7.5 and 6.5, respectively, and to sustain the production of VC and ethene. Diopside gradually lost its buffering capacity during the first 84 days due to the formation of a low reactive leached layer but dechlorination to cis-DCE was still achieved. Among the three minerals tested, forsterite was identified as the best buffering agent. Its presence led to the best PCE removal performance and the highest relative abundance of Dehalococcoides. This study showed that forsterite and fayalite are promising sources of long-term pH buffering for in situ bioremediation of source-zone PCE.
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Affiliation(s)
- Elsa Lacroix
- Ecole Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering (ENAC), Ecological Engineering Laboratory, Lausanne, Switzerland; Ecole Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering (ENAC), Laboratory for Environmental Biotechnology, Lausanne, Switzerland
| | - Alessandro Brovelli
- Ecole Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering (ENAC), Ecological Engineering Laboratory, Lausanne, Switzerland
| | - Julien Maillard
- Ecole Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering (ENAC), Laboratory for Environmental Biotechnology, Lausanne, Switzerland
| | - Emmanuelle Rohrbach-Brandt
- Ecole Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering (ENAC), Laboratory for Environmental Biotechnology, Lausanne, Switzerland
| | - D A Barry
- Ecole Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering (ENAC), Ecological Engineering Laboratory, Lausanne, Switzerland
| | - Christof Holliger
- Ecole Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering (ENAC), Laboratory for Environmental Biotechnology, Lausanne, Switzerland.
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11
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Koenig JC, Groissmeier KD, Manefield MJ. Tolerance of anaerobic bacteria to chlorinated solvents. Microbes Environ 2014; 29:23-30. [PMID: 24441515 PMCID: PMC4041229 DOI: 10.1264/jsme2.me13113] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Accepted: 11/08/2013] [Indexed: 11/12/2022] Open
Abstract
The aim of this research was to evaluate the effects of four chlorinated aliphatic hydrocarbons (CAHs), perchloroethene (PCE), carbon tetrachloride (CT), chloroform (CF) and 1,2-dichloroethane (1,2-DCA), on the growth of eight anaerobic bacteria: four fermentative species (Escherichia coli, Klebsiella sp., Clostridium sp. and Paenibacillus sp.) and four respiring species (Pseudomonas aeruginosa, Geobacter sulfurreducens, Shewanella oneidensis and Desulfovibrio vulgaris). Effective concentrations of solvents which inhibited growth rates by 50% (EC50) were determined. The octanol-water partition coefficient or log Po/w of a CAH proved a generally satisfactory measure of its toxicity. Most species tolerated approximately 3-fold and 10-fold higher concentrations of the two relatively more polar CAHs CF and 1,2-DCA, respectively, than the two relatively less polar compounds PCE and CT. EC50 values correlated well with growth rates observed in solvent-free cultures, with fast-growing organisms displaying higher tolerance levels. Overall, fermentative bacteria were more tolerant to CAHs than respiring species, with iron- and sulfate-reducing bacteria in particular appearing highly sensitive to CAHs. These data extend the current understanding of the impact of CAHs on a range of anaerobic bacteria, which will benefit the field of bioremediation.
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Affiliation(s)
- Joanna C. Koenig
- Centre for Marine Bioinnovation, School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
| | - Kathrin D. Groissmeier
- Helmholtz Institute of Groundwater Ecology, Ingolstaedter Landstrasse 1, D-85764, Neuherberg, Germany
| | - Mike J. Manefield
- Centre for Marine Bioinnovation, School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
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Dillehay JL, Bowman KS, Yan J, Rainey FA, Moe WM. Substrate interactions in dehalogenation of 1,2-dichloroethane, 1,2-dichloropropane, and 1,1,2-trichloroethane mixtures by Dehalogenimonas spp. Biodegradation 2013; 25:301-12. [DOI: 10.1007/s10532-013-9661-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 08/22/2013] [Indexed: 12/01/2022]
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13
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Philips J, Maes N, Springael D, Smolders E. Acidification due to microbial dechlorination near a trichloroethene DNAPL is overcome with pH buffer or formate as electron donor: experimental demonstration in diffusion-cells. JOURNAL OF CONTAMINANT HYDROLOGY 2013; 147:25-33. [PMID: 23500838 DOI: 10.1016/j.jconhyd.2013.02.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 01/08/2013] [Accepted: 02/01/2013] [Indexed: 06/01/2023]
Abstract
Acidification due to microbial dechlorination of trichloroethene (TCE) can limit the bio-enhanced dissolution of TCE dense non-aqueous phase liquid (DNAPL). This study related the dissolution enhancement of a TCE DNAPL to the pH buffer capacity of the medium and the type of electron donor used. In batch systems, dechlorination was optimal at pH7.1-7.5, but was completely inhibited below pH6.2. In addition, dechlorination in batch systems led to a smaller pH decrease at an increasing pH buffer capacity or with the use of formate instead of lactate as electron donor. Subsequently, bio-enhanced TCE DNAPL dissolution was quantified in diffusion-cells with a 5.5 cm central sand layer, separating a TCE DNAPL layer from an aqueous top layer. Three different pH buffer capacities (2.9 mM-17.9 mM MOPS) and lactate or formate as electron donor were applied. In the lactate fed diffusion-cells, the DNAPL dissolution enhancement factor increased from 1.5 to 2.2 with an increase of the pH buffer capacity. In contrast, in the formate fed diffusion-cells, the DNAPL dissolution enhancement factor (2.4±0.3) was unaffected by the pH buffer capacity. Measurement of the pore water pH confirmed that the pH decreased less with an increased pH buffer capacity or with formate instead of lactate as electron donor. These results suggest that the significant impact of acidification on bio-enhanced DNAPL dissolution can be overcome by the amendment of a pH buffer or by applying a non acidifying electron donor like formate.
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Affiliation(s)
- Jo Philips
- Department of Earth and Environmental Sciences, Division of Soil and Water Management, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee, Belgium.
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Philips J, Haest PJ, Springael D, Smolders E. Inhibition of Geobacter dechlorinators at elevated trichloroethene concentrations is explained by a reduced activity rather than by an enhanced cell decay. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:1510-1517. [PMID: 23281888 DOI: 10.1021/es303390q] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Microbial dechlorination of trichloroethene (TCE) is inhibited at elevated TCE concentrations. A batch experiment and modeling analysis were performed to examine whether this self-inhibition is related to an enhanced cell decay or a reduced dechlorination activity at increasing TCE concentrations. The batch experiment combined four different initial TCE concentrations (1.4-3.0 mM) and three different inoculation densities (4.0 × 10(5) to 4.0 × 10(7)Geobacter cells·mL(-1)). Chlorinated ethene concentrations and Geobacter 16S rRNA gene copy numbers were measured. The time required for complete conversion of TCE to cis-DCE increased with increasing initial TCE concentration and decreasing inoculation density. Both an enhanced decay and a reduced activity model fitted the experimental results well, although the reduced activity model better described the lag phase and microbial decay in some treatments. In addition, the reduced activity model succeeded in predicting the reactivation of the dechlorination reaction in treatments in which the inhibiting TCE concentration was lowered after 80 days. In contrast, the enhanced decay model predicted a Geobacter cell density that was too low to allow recovery for these treatments. Conclusively, our results suggest that TCE self-inhibition is related to a reduced dechlorination activity rather than to an enhanced cell decay at elevated TCE concentrations.
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Affiliation(s)
- Jo Philips
- Division of Soil and Water Management, Department of Earth and Environmental Sciences, KU Leuven (University of Leuven), Kasteelpark Arenberg 20, B-3001 Heverlee, Belgium
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15
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Maness AD, Bowman KS, Yan J, Rainey FA, Moe WM. Dehalogenimonas spp. can Reductively Dehalogenate High Concentrations of 1,2-Dichloroethane, 1,2-Dichloropropane, and 1,1,2-Trichloroethane. AMB Express 2012; 2:54. [PMID: 23046725 PMCID: PMC3492069 DOI: 10.1186/2191-0855-2-54] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 10/02/2012] [Indexed: 11/30/2022] Open
Abstract
The contaminant concentrations over which type strains of the species Dehalogenimonas alkenigignens and Dehalogenimonas lykanthroporepellens were able to reductively dechlorinate 1,2-dichloroethane (1,2-DCA), 1,2-dichloropropane (1,2-DCP), and 1,1,2-trichloroethane (1,1,2-TCA) were evaluated. Although initially isolated from an environment with much lower halogenated solvent concentrations, D. alkenigignens IP3-3T was found to reductively dehalogenate chlorinated alkanes at concentrations comparable to D. lykanthroporepellens BL-DC-9T. Both species dechlorinated 1,2-DCA, 1,2-DCP, and 1,1,2-TCA present at initial concentrations at least as high as 8.7, 4.0, and 3.5 mM, respectively. The ability of Dehalogenimonas spp. to carry out anaerobic reductive dechlorination even in the presence of high concentrations of chlorinated aliphatic alkanes has important implications for remediation of contaminated soil and groundwater.
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Affiliation(s)
- Andrew D Maness
- Department of Civil and Environmental Engineering, Louisiana State University, 3513B Patrick Taylor Hall, Baton Rouge, LA, 70803, USA
| | - Kimberly S Bowman
- Department of Civil and Environmental Engineering, Louisiana State University, 3513B Patrick Taylor Hall, Baton Rouge, LA, 70803, USA
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Jun Yan
- Department of Civil and Environmental Engineering, Louisiana State University, 3513B Patrick Taylor Hall, Baton Rouge, LA, 70803, USA
- Present address: Jun Yan, Department of Microbiology and Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN, USA
| | - Fred A Rainey
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK, 99508, USA
| | - William M Moe
- Department of Civil and Environmental Engineering, Louisiana State University, 3513B Patrick Taylor Hall, Baton Rouge, LA, 70803, USA
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Rittmann S, Herwig C. A comprehensive and quantitative review of dark fermentative biohydrogen production. Microb Cell Fact 2012; 11:115. [PMID: 22925149 PMCID: PMC3443015 DOI: 10.1186/1475-2859-11-115] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 08/03/2012] [Indexed: 01/25/2023] Open
Abstract
Biohydrogen production (BHP) can be achieved by direct or indirect biophotolysis, photo-fermentation and dark fermentation, whereof only the latter does not require the input of light energy. Our motivation to compile this review was to quantify and comprehensively report strains and process performance of dark fermentative BHP. This review summarizes the work done on pure and defined co-culture dark fermentative BHP since the year 1901. Qualitative growth characteristics and quantitative normalized results of H2 production for more than 2000 conditions are presented in a normalized and therefore comparable format to the scientific community.Statistically based evidence shows that thermophilic strains comprise high substrate conversion efficiency, but mesophilic strains achieve high volumetric productivity. Moreover, microbes of Thermoanaerobacterales (Family III) have to be preferred when aiming to achieve high substrate conversion efficiency in comparison to the families Clostridiaceae and Enterobacteriaceae. The limited number of results available on dark fermentative BHP from fed-batch cultivations indicates the yet underestimated potential of this bioprocessing application. A Design of Experiments strategy should be preferred for efficient bioprocess development and optimization of BHP aiming at improving medium, cultivation conditions and revealing inhibitory effects. This will enable comparing and optimizing strains and processes independent of initial conditions and scale.
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Affiliation(s)
- Simon Rittmann
- Institute of Chemical Engineering, Research Area Biochemical Engineering, Gumpendorferstraße 1a, Vienna University of Technology, Vienna, 1060, Austria
| | - Christoph Herwig
- Institute of Chemical Engineering, Research Area Biochemical Engineering, Gumpendorferstraße 1a, Vienna University of Technology, Vienna, 1060, Austria
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Tracy BP, Jones SW, Fast AG, Indurthi DC, Papoutsakis ET. Clostridia: the importance of their exceptional substrate and metabolite diversity for biofuel and biorefinery applications. Curr Opin Biotechnol 2012; 23:364-81. [DOI: 10.1016/j.copbio.2011.10.008] [Citation(s) in RCA: 313] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 10/06/2011] [Accepted: 10/20/2011] [Indexed: 12/19/2022]
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Philips J, Hamels F, Smolders E, Springael D. Distribution of a dechlorinating community in relation to the distance from a trichloroethene dense nonaqueous phase liquid in a model aquifer. FEMS Microbiol Ecol 2012; 81:636-47. [PMID: 22512272 DOI: 10.1111/j.1574-6941.2012.01395.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 03/27/2012] [Accepted: 04/11/2012] [Indexed: 11/30/2022] Open
Affiliation(s)
- Jo Philips
- Division of Soil and Water Management; Katholieke Universiteit Leuven; Heverlee; Belgium
| | - Fanny Hamels
- Division of Soil and Water Management; Katholieke Universiteit Leuven; Heverlee; Belgium
| | - Erik Smolders
- Division of Soil and Water Management; Katholieke Universiteit Leuven; Heverlee; Belgium
| | - Dirk Springael
- Division of Soil and Water Management; Katholieke Universiteit Leuven; Heverlee; Belgium
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Rao JU, Rash BA, Nobre MF, da Costa MS, Rainey FA, Moe WM. Actinomyces naturae sp. nov., the first Actinomyces sp. isolated from a non-human or animal source. Antonie van Leeuwenhoek 2011; 101:155-68. [PMID: 21965039 DOI: 10.1007/s10482-011-9644-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2011] [Accepted: 09/16/2011] [Indexed: 10/17/2022]
Abstract
Three facultatively anaerobic, Gram-positive staining, rod-shaped, non-spore forming, flagellated bacterial strains, BL-75, BL-79(T) and BL-104, were isolated from chlorinated solvent-contaminated groundwater. Phylogenetic analysis based on 16S rRNA gene sequence comparisons showed them to represent a distinct lineage within the genus Actinomyces with sequence identities in the range of <88-95.4% with previously described Actinomyces species. The strains were oxidase and catalase negative. Nitrate was not reduced. Esculin was hydrolyzed. Growth occurred in the temperature range of 20-43°C (optimum 30-37°C) and pH range 4.5-9.0 (optimum pH 6.5). Substrates supporting growth included various mono-, di-, and tri-saccharides. The end products of glucose fermentation were acetate, lactate, succinate and formate. Fermentative growth was observed in the presence of near saturation concentrations of perchloroethene (PCE) and toluene and in the presence of 1,2-dichloroethane and 1,1,2-trichloroethane at concentrations up to at least 24.4 mM and 11.2 mM, respectively. The dominant cellular fatty acids when grown in peptone/yeast extract/glucose (PYG) medium were C(18:1) ω9c, C(16:0), and C(14:0). The peptidoglycan was found to contain the amino acids alanine, glutamic acid, lysine, and ornithine at approximate molar ratios of 1.7 Ala: 2.3 Glu: 1.3 Lys: 1.0 Orn. The cell wall sugars were found to include rhamnose and mannose. The polar lipids were found to include diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phospholipid (PL), phosphoglycolipids (PGL), and glycolipids (GL). The main respiratory quinone of strain BL-79(T) was MK-9(H(4)), with minor components MK-10(H(4)) and MK-8(H(4)). The DNA mol% G+C content of the type strain is 69.8%. On the basis of phylogenetic and phenotypic characteristics, these strains could be differentiated from previously described species of the genus Actinomyces. Strains BL-75, BL-79(T) and BL-104 are designated as a novel species, for which the name Actinomyces naturae sp. nov. is proposed. This is the first Actinomyces species isolated from an environmental rather than human or animal sources. The type strain of Actinomyces naturae is BL-79(T) (= CCUG 56698(T) = NRRL B-24670(T)).
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Affiliation(s)
- Jyoti U Rao
- Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA 70803, USA
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20
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Clostridium hydrogeniformans sp. nov. and Clostridium cavendishii sp. nov., hydrogen-producing bacteria from chlorinated solvent-contaminated groundwater. Int J Syst Evol Microbiol 2010; 60:358-363. [DOI: 10.1099/ijs.0.013169-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Four hydrogen-producing, aerotolerant, anaerobic bacterial strains isolated from chlorinated solvent-contaminated groundwater were characterized using a polyphasic approach. Three of the strains, designated BL-18, BL-19 and BL-20T, were found to be identical in 16S rRNA gene sequences and in phenotypic properties. Cells of these strains are Gram-positive-staining, spore-forming, motile rods with peritrichous flagella. Growth occurred at 15–40 °C, pH 5.0–10.0 and at NaCl concentrations up to 5 % (w/v). Acid was produced in fermentation of cellobiose, fructose, galactose (weak), glucose, maltose and salicin. Products of fermentation in PYG medium were acetate, butyrate, ethanol, formate, carbon dioxide and hydrogen. Dominant cellular fatty acids when grown in PYG medium were C13 : 0 iso, C16 : 0, C13 : 0 anteiso, C15 : 0 iso and C15 : 0 anteiso. The genomic DNA G+C content was 30.4 mol%. These isolates can be differentiated from their closest phylogenetic relative, the cluster I Clostridium species Clostridium frigidicarnis (97.2 % similar to the type strain in 16S rRNA gene sequence), on the basis of phenotypic and chemotaxonomic properties. The other strain characterized in this study, BL-28T, was Gram-positive-staining with spore-forming, rod-shaped cells. Growth occurred at 15–46 °C, pH 6.0–8.5 and at NaCl concentrations up to 3 % (w/v). Acid was produced from cellobiose, dextran, fructose (weak), glucose, maltose, salicin and trehalose. End products of PYG fermentation included acetate, butyrate, pyruvate, carbon dioxide and hydrogen. Dominant cellular fatty acids from cells grown in PYG medium at 30 °C were C14 : 0, C14 : 0 dimethyl aldehyde, C16 : 0 and C12 : 0. The DNA G+C content was 28.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain BL-28T falls within cluster I of the genus Clostridium, but with ≤95.2 % identity with previously described species. On the basis of results presented here, strains BL-20T (=NRRL B-51348T =DSM 21757T) and BL-28T (=NRRL B-51352T =DSM 21758T) are proposed as the type strains of novel species of the genus Clostridium with the names Clostridium hydrogeniformans sp. nov. and Clostridium cavendishii sp. nov., respectively.
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Watanabe K, Manefield M, Lee M, Kouzuma A. Electron shuttles in biotechnology. Curr Opin Biotechnol 2009; 20:633-41. [DOI: 10.1016/j.copbio.2009.09.006] [Citation(s) in RCA: 192] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Revised: 09/10/2009] [Accepted: 09/12/2009] [Indexed: 10/20/2022]
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