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Grant 1R01ES024255-01 Lisa Alvarez-Cohen Presenter: Shan Yi 04/22/2019
Metabolic Interactions Supporting Effective TCE Bioremediation under Biogeochemical Conditions Grant 1R01ES Lisa Alvarez-Cohen Presenter: Shan Yi 04/22/2019
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Anaerobic Microbial Reductive Dechlorination
PCE TCE cis-DCE VC ETH Cl- Cl- Cl- Cl- H2 H2 H2 H2 Dehalococcoides mccartyi (Dhc) Clostridium, Dehalobacter, Dehalospirillum, Desulfitobacterium, Desulfomonile, Desulfuromonas, Sulfurospirillum, Geobacter, etc Complete dechlorination Partial dechlorination Electron acceptors: chlorinated ethenes Electron donor: H2 Carbon source: acetate, CO2 Coenzymes: corrinoids (vitaminB12) Toxic waste: CO
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Interactions in Dechlorinating Communities
Dhc does not live alone in nature. Organic Substrate (lactate/whey/molasses) CO2 CO2 Hydrogenotrophic Acetogens Fermenters Methanogens Corrinoids (e.g., Vitamin B12) CO Acetate H2 TCE Ethene Dehalococcoides mccartyi 3 3
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Geochemical Perturbations on TCE Bioremediation
Important to determine how environmental conditions affect material exchanges in TCE-dechlorinating communities. Injection wells Soil Chlorinated solvents Groundwater Cl- Na+
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Technical Objectives and Approach
1) Construct defined consortia representing major interactions crucial to TCE-bioremediation 2) Investigate consortia performance in the presence of sulfate reduction or high salinity Defined consortia qPCR TCE Ethene Expression array Insight into engineering solutions Cell activity & metabolite exchange RNA-seq analysis 3) Apply either microarray or RNA-seq to elucidate the effects of perturbation on metabolism and functions of Dhc. 4) Possible solutions to overcome the perturbation.
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Effects of Sulfate Reduction on TCE-dechlorination
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Electron donor competition
Sulfate Effects Sulfate is prevalent in groundwater. Sulfate-reducing bacteria often occur in the same niche with dechlorinating bacteria. SO42- +4H2 +H+ HS-+ 4H2O Lack of consistent understanding of sulfate’s effects on TCE dechlorination. Two testing hypotheses: Inhibitory effects of sulfate or sulfide Competition of electron donor (H2) Pure culture Toxicity effects Consortia Complex enrichment Electron donor competition Two scenarios: 1) electron acceptor limiting, 2) electron donor limiting
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Two Types of Syntrophic Consortia
Bacterium Function Desulfovibrio vulgaris Hildenborough (DvH) Fermentation, sulfate reduction Syntrophomonas wolfei (S. wolfei) Fermentation Dehalococcoides mccartyi strain 195 (Dhc 195) TCE dechlorination Scenario 1: electron acceptor limiting Scenario 2: electron donor limiting Lactate Dhc195 DvH Acetate + H2 VC & Ethene TCE Sulfate Sulfide Butyrate S. wolfei Acetate + H2 VC & Ethene TCE Sulfate Sulfide DvH Dhc195 CO Butyrate S. wolfei H2 VC & Ethene TCE Sulfate Sulfide DvH Dhc195 CO
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Inhibitory Effects on Syntrophic Consortia Members
SO42- HS- Axenic cultures Function Sulfate Sulfide Dhc 195 TCE dechlorination 5 mM No effects Decreased yield by 65% S. wolfei Fermentation Decreased yield by 40% DvH Fermentation, sulfate reduction N/A >10 mM Cell growth inhibited Mao et al. Appl. Environ. Microbiol. 2017
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Sulfide Inhibition on Dhc195
Decreased TCE dechlorination rates. Decoupled growth from dechlorination when sulfide was introduced. Transcriptomic analysis using microarray indicates the gene expression changes in ATP synthase, biosynthesis, and metal-containing enzymes. Mao et al. Appl. Environ. Microbiol. 2017
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Effects of Sulfate Reduction on TCE-dechlorination
Dhc195:DvH: ~5:1 Scenario 1: electron acceptor limiting Lactate Dhc195 DvH Acetate H2 VC & Ethene TCE DvH Sulfate Sulfide Dhc195 CO in pure Dhc195 CO CO in DvH/Dhc195 coculture Men et al., ISME J, 2012 , Polasko et al., AGU,2014, Zhuang et al., PNAS 2014
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Co-Culture DvH/Dhc195 under Electron Acceptor Limitation
Unlimited H2 production Dhc195:DvH: ~1:6 Inhibited TCE dechlorination Mao et al. Appl. Environ. Microbiol. 2017
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Tri-Culture S. wolfei/DvH/Dhc195 under Electron Donor Limitation
No Inhibition on TCE dechlorination CO Butyrate S. wolfei Acetate + H2 VC & Ethene TCE Sulfate Sulfide DvH Dhc195 Dhc195:DvH:S.wolfei: ~16:1:1 Mao et al. Appl. Environ. Microbiol. 2017
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Effects of Sulfate Reduction on TCE-Dechlorinating Enrichment Culture
Lactate Enrichment culture showed similar inhibitory patterns as the defined consortia under the two limitation conditions. Methane production occurred in the control culture but not in sulfate amended groups due to low H2 concentration. ANAS: a methanogenic reductive-dechlorinating enrichment culture Mao et al. Appl. Environ. Microbiol. 2017
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Effects of Salinity on TCE-dechlorination
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Salinity Effects on TCE bioremediation
TCE is present at 389 National Priorities List (NPL) sites, many of which are along the coast. Effects of salinity on TCE bioremediation are unknown. Two testing hypotheses: Salt stress at the cellular level of Dhc Salt stress on the metabolic interactions Bacterium Function DvH Fermentation Pelosinus fermentans R7 (PfR7) Fermentation, corrinoid production Dhc 195 TCE dechlorination Salinity stress Two scenarios: Inhibitory effects 1) Existing salinity in groundwater 2) Salinity perturbation Pure culture Consortia
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Tri-Culture of PfR7/DvH/Dhc195 under Salt Stress
Lactate PfR7 Dhc195 DvH Propionate Acetate H2 Corrinoids VC & Ethene TCE CO
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Salt Stress on Consortium Members
Group Control A B C D E F G H I J Na+ conc. after perturbation (mM) 50 183 227 271 315 359 404 448 492 536 580 Limiting factor for TCE dechlorination N/A PfR7 Limiting PfR7 & DvH Limiting Dhc195 Limiting Partially restored growth by GB Significant enhancement by GB 100% PfR7 DvH 80% Glycine betaine (GB) 2 mM 13% Sun et al. In preparation 2019
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Overall Salt Stress Response of Dhc195 Pure Culture
No effects MIC MIC = Minimum inhibitory concentration stressor concentration that decreases the overall yield by 50% Ectoine Proline Glycine betaine Sun et al. In preparation 2019
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Schematic diagram for Dhc195 pure culture salt perturbation experiment
Transcriptional Responses of Dhc195 Pure Culture under Salinity Perturbation Biosynthesis: Acetyl-CoA synthesis Pyruvate synthesis Glutamate/glutamine biosynthesis DNA/RNA synthesis Riboflavin metabolism tRNA synthetase Energy metabolism: NADH dehydrogenases ATP synthases ABC transporters 383 mM Schematic diagram for Dhc195 pure culture salt perturbation experiment Sun et al. In preparation 2019
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Effects on Metabolic Interactions under Salt Stress (I)
Group Control A B C D E F G H I J Na+ conc. after perturbation (mM) 50 183 227 271 315 359 404 448 492 536 580 Limiting factor for TCE dechlorination N/A PfR7 Limiting PfR7 & DvH Limiting Dhc195 Limiting 1st dose of TCE + salt perturbation Time Amount of TCE/bottle Compare dechlorination kinetics & cell growth during this period Sun et al. In preparation 2019
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Effects on Metabolic Interactions under Salt Stress (I)
Group Control A B C D E F G H I J Na+ conc. after perturbation (mM) 50 183 227 271 315 359 404 448 492 536 580 Limiting factor for TCE dechlorination N/A PfR7 Limiting PfR7 & DvH Limiting Dhc195 Limiting GB slightly improved TCE dechlorination Sun et al. In preparation 2019
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Effects on Metabolic Interactions under Salt Stress (II)
Group Control A B C D E F G H I J Na+ conc. after perturbation (mM) 50 183 227 271 315 359 404 448 492 536 580 Limiting factor for TCE dechlorination N/A PfR7 Limiting PfR7 & DvH Limiting Dhc195 Limiting 1st dose of TCE 2st dose of TCE + salt perturbation + GB Time Amount of TCE/bottle Compare dechlorination kinetics & cell growth during this period Sun et al. In preparation 2019
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Effects on Metabolic Interactions under Salt Stress (II)
Group Control A B C D E F G H I J Na+ conc. after perturbation (mM) 50 183 227 271 315 359 404 448 492 536 580 Limiting factor for TCE dechlorination N/A PfR7 Limiting PfR7 & DvH Limiting Dhc195 Limiting Amendment with GB Sun et al. In preparation 2019
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Effects on Metabolic Interactions under Salt Stress (II)
Group Control A B C D E F G H I J Na+ conc. after perturbation (mM) 50 183 227 271 315 359 404 448 492 536 580 Limiting factor for TCE dechlorination N/A PfR7 Limiting PfR7 & DvH Limiting Dhc195 Limiting Amendment with GB + vitamin B12 Severe inhibition Sun et al. In preparation 2019
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Summary Sulfate effects
Sulfide (5mM) inhibited TCE dechlorination and growth of Dhc195. When hydrogen was abundant, sulfate-reducing bacterial activity generated sulfide that inhibited TCE dechlorination. The sulfate-reduction activity can be limited by using slow fermentable substrates to prioritize TCE dechlorination. Salt stress Dhc195 has a relatively higher tolerance to salt stress compared to supporting bacteria that formed syntrophic interactions with Dhc. The salt stress mostly caused the transcriptional changes in genes encoding catabolism, tRNA, amino acid, and nucleic acid biosynthesis in Dhc. Osmoprotectant, i.e., GB can be used to ameliorate the inhibition on the supporting bacteria. Biostimulation with medium containing cobalamin and GB is necessary to sustain the bioremediation performance under salt perturbation at concentrations up to 400 mM.
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Acknowledgements Thank you! Questions?
Alvarez-Cohen’s lab at UC Berkeley Prof. Lisa Alvarez-Cohen Mohan Sun Dr. Xinwei Mao Alexandra Polasko Thank you! Questions? 27
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