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Principles and Prospects for PCB Bioremediation in Soils and Sediments

Explore current biological principles for PCB bioremediation, anaerobic/aerobic treatment rationale, chromatographic profiles, occurrence in various sites, FeSO4 amendment's effect, recombinant PCB degradation pathways, anaerobic reductive dechlorination, and genetic tracking in soil.

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Principles and Prospects for PCB Bioremediation in Soils and Sediments

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  1. PRINCIPLES AND PROSPECTS FOR BIOREMEDIATION OF PCBs IN SOILS AND SEDIMENTS James M. TIEDJE Distinguished Professor and Director Center For Microbial Ecology Michigan State University tiedjej@msu.edu 1

  2. Current Biological Principles For Bioremediation Of PCBs  Highly chlorinated PCBs (Aroclors) can be reduced to a lesser chlorinated species by anaerobic dehalogenating communities  The lesser chlorinated PCB species can be oxidized by aerobic biphenyl degraders yielding chlorinated benzoates, pentadienes and HOPDAs  Chlorobenzoates can be mineralized by yet another group of bacteria  These three independently occurring processes can be combined in a singular two-phase anaerobic-aerobic remediation scheme 2

  3. Rationale for anaerobic/aerobic biotreatment Less aerobically degradable More aerobically degradable Some componentsof Aroclor 1242(commercial PCB mixture) Intermediatedechlorination products Advanceddechlorination products 3

  4. Chromatographic Profiles - Pattern 4

  5. Congener Specificity 5

  6. Evaluation of in situ PCB Dechlorination 6

  7. Occurrence of PCB Dechlorination • Acushnet Estuary (MA) • Hudson River • Industrial lagoons • River Raisin (MI) • Sheboygan River (WI) • Silver Lake (MA) • Escambia Bay (FL) • Hoosic River (MA) • Lake Ketelmeer/Rhine River (Netherlands) • Waukegan Harbor (IL) • Wood's Pond (MA) Observed extent of dechlorination tends to taper off below 50 to 100 ppm. 7

  8. FeSO4 AmendmentExtent of Dechlorination 8

  9. Effect of FeSO4 on Aroclor 1242 Dechlorinationby Hudson River Microorganisms No amendment: Process M (meta) dechlorination 25% of Cl removed Ortho & para substituted products: 2-CB, 2,2’-CB, 26-CB, 2,4’-CB, 2,2’,4-CB, 2,4,4’-CB With FeSO4: Adds process Q (para) dechlorination 50% of Cl removed Ortho substituted products: 2-CB, 2,2’-CB, 2,6-CB 9

  10. Sequential InoculationsExtent of Dechlorination 10

  11. Importance of PCB Dechlorination • Is an intrinsic process • Has potential for bioremediation • Products are more aerobically degradable • Products are generally less toxic • But, degradation is usually incomplete withespecially ortho-PCBs remaining, hence, an aerobic phase is needed 11

  12. Barriers to Aerobic Biodegradation • Limited to lesser chlorinated congeners • Co-metabolic • Requires induction • Yields no growth • Incomplete - accumulates potentially problematic compounds 12

  13. Recombinant PCB degradation Pathways 13

  14. rodB catA fcbB 4CBA 4HBA 24dCBA 24dCBA 4CBA 4HBA 24dCBA 4CBA 4HBA RT RT RT RT RT RT RT RT RT - - + + + - + - + + + - + + - - - - 2.0 Kb 1.5 Kb 600 bp 500 bp 400 bp 300 bp 200 bp 100 bp C O O H  Halohydroxyperoxidase/ catalase (catA) to use for upgrading pathway for ortho + para-PCBs  The catA is related to (bromo) hydroxyperoxidases for anoxic chlorination/dechlorination of chloramphenicol  The laboratory evolution to target enzyme(s) for reductive dechlorination of both CBAs and PCBs  The catA family members to use for the combinatorial mutagenesis rod/cat+ fcb genes O H C O O H Central pathways C l bphABCD C l + 5-C aliphatic hydrocarbons ohb genes O H O H Differential expression of dehalogenases in response to CBAs. Reverse transcription (RT)-PCR of total RNA from Nocardioides sp. KZ4N. 14

  15. Anaerobic Reductive Dechlorination FeSO4 • Rates/Conc. Seed Inoculum Surfactants • Mixed culture • Sorption/Availability Aerobic PCB Dechlorination And Growth Genes Organisms • ohb, fcb, rod, clc • Burkholderia sp. LB400(ohb) (G-) • G+/- Cassette • Rhodococcus erythropolis RHA1(fcb) (G+) Surfactants • Toxicity/Growth Inocula Technology • Carrier Media PCB Remediation Toolbox • Ex-Situ BioReactor • low, medium, high • density solids 15

  16. Schematic Representation of the Sediment Experiment 106 cells/g 104 cells/g Non-inoculated Non-contaminated 1 g of soil 1 g of soil 0.25 g of soil DNA extraction Serial dilution PCB extraction and analysis Luria-Bertani Medium with Rifampicin 50 g/ml Whole cell PCR for isolated colonies (fcb and ohb primers) Real Time PCR 16

  17. Molecular Tracking of RHA 1 (fcbB) in Picatinny Arsenal Soil Using Real Time PCR 40 2 R = 0.9816 35 RHA 1 in Soil (CFUs) 30 Plasmid pRHD34 (copy #) RHA1 Whole Cell DNA (copy #) 25 Ct 20 15 2 R = 0.9984 10 2 R = 0.9964 5 0 -4 1 6 11 16 21 26 31 ln CFUS or Copy Number 17

  18. Population dynamics of RHA1(fcb) and LB400(ohb) during aerobic treatment of Aroclor 1242 anaerobic dechlorination products (Red Cedar River sediment) 108 108 106 cells/g of sediment 104 cells/g of sediment 107 107 RHA1(fcb) plate counts 106 106 LB400(ohb) plate counts TaqMan-16S rDNA probe 105 105 TaqMan-fcb probe 104 104 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 CFUs/g of sediment (counted or calculated) 108 108 Non-contaminated Non-inoculated 107 107 106 106 105 105 104 104 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 Time (days) 18

  19. Laboratory scale two-phase PCB remediation (Red Cedar River sediment)  Enhanced anaerobic dechlorination of Aroclor resulted in shifting from highly to lower chlorinated congeners  Bioaugmentation with engineered aerobic G+/G- GEM cassette LB400(ohb)+RHA1(fcb) resulted in efficient degradation of the remaining PCBs 19

  20. PCB-growing Dechlorinating GEM Advantages  Increased biomass smaller inoculum  Reduced HOPDA diminished toxicity  Issues remaining: Still incomplete mineralization of higher chlorinated PCB species lower degradation rates, incomplete Cl-HOPDA removal Effect of the ohb (pRO41) and fcb(pRHD34) genes on PCB degradation Mix M, nom.1 mM Mix C, nom. 1 mM Strain(plasmid)/ inducer - - Cl HOPDA Cl % PCB degraded % PCB degraded HOPDA OD OD l Release, Release, =394 600 600 l =394 mM mM LB400(pRT1) 83.8 0.19 1.33 0.476 93.7 0.21 0.91 0.066 Bph Not LB400(pRO41) 75 0.24 1.98 0.164 93.2 0.35 1.47 detected 25CBA LB400(pRO41) 67.6 0.19 91.3 1.5 0.139 0.30 1.42 0.069 25CBA + RHA1(pRHD34) 4CBA 20

  21. Biological ActivityDechlorination of Congeners with AhR-Mediated Activity * ** 21

  22. AhR Mediated Toxicity Reduction 22

  23. Biological Activity Summary 23

  24. Genome of Burkholderia Strain LB400 • Best known PCB degrader sequenced • 9.5 Megabases, largest bacterial genome yet sequenced • Has multiple chromosomes • Has many aromatic degradation genes 24

  25. Differential Expression by a PCB Degrader 4,000 genes of Burkholderia strain LB400 Genes (mRNA) expressed during growth on succinate (green, Cy3) vs. genes expressed during growth or rich media (red, Cy5), and expressed under both conditions (yellow) 25

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