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Objective

de Lipathay et al. 2003. In situ exposure to low herbicide concentrations affects microbial population composition and catabolic gene frequency in an aerobic shallow aquifer. Appl. Environ. Microbiol . 69: 461-467. Objective.

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Objective

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  1. de Lipathayet al. 2003. In situ exposure to low herbicide concentrations affects microbial population composition and catabolic gene frequency in an aerobic shallow aquifer. Appl. Environ. Microbiol. 69: 461-467.

  2. Objective • To evaluate how the in situ exposure of the Vejen aquifer to low phenoxyacid herbicide concentrations affected the indigenous microbial community composition Aquifer = an underground bed or layer of permeable rock, sediment, or soil that contains water and releases it in appreciable amounts; water-bearing zone.

  3. 2,4-dichlorophenoxyacetic acid (2,4-D) Mecoprop = 2-(2-methyl-4-chlorophenoxy)propionic acid Dichlorprop = 2-(2,4-dichlorophenoxy)propionic acid Aquifer contaminated with a mixture of mecoprop, dichlorprop, 2-,ethyl-4,6-dinitrophenol (DNOC), bentazone, isoproturon, 2,4-dichlorbenzamide continuously for 216 days, bromide as tracer

  4. 40 µg/L of each herbicideinjected for 216 days, samples in Fig. 3 taken 40 days later

  5. Techniques used • Enumeration • Metabolism

  6. Techniques used • Enumeration • Cultivation: • Non-cultivation: • Metabolism • Degradation: • Mineralization:

  7. Techniques used • Enumeration • Cultivation: CFUs, MPN • Non-cultivation: DAPI, molecular biology techniques 16S rDNA (MPN-PCR, general bacteria (PRBA338f and PRUN518r), Pseudomonas (PSMGf and 785r) • Metabolism • Degradation: MPN (25% contaminant disappearance), 16S rDNA(population with tdf gene via RFLP) • Mineralization: MPN (25% 14C-CO2)

  8. Strengths and weaknesses of techniques • Microscopic – DAPI • Cultivation techniques • Water agar, Gould’s S1 • Phenoxyacid degraders • Molecular biology techniques • Bacteria, Pseudomonas, tdf A, B, C • Whole community DNA was extracted • Primers for ….

  9. 40 days later

  10. MPN-PCR

  11. No Pseudomonas on Gould’s but detected with 16S rDNA Pseudomonas in acclimated sediment Role of Pseudomonas in degradation? Mineralization study?

  12. MPN-25% degradation

  13. MPN-25% degradation - RFLP patterns in B2 different from others - tdf no homology with known sequences

  14. Restriction endonucleases Specific recognition sites 4-6 basepairs

  15. To evaluate how the in situ exposure of the Vejen aquifer to low phenoxyacid herbicide concentrations affected the indigenous microbial community composition • Was objective achieved? • Continuous exposure can markedly affect composition of bacterial community of a subsurface aquifer • Increase in culturability, Pseudomonas, phenoxyacid degraders, bacteria with tdf genes

  16. Phenoxyacid herbicides • 2,4-D = 2,4-dichlorophenoxyacetic acid • Mecoprop= 2-(2-methyl-4-chlorophenoxy) propionicacid • Dichlorprop = 2-(2,4-dichlorophenoxy)propionic acid

  17. Stainless steel piston sampler

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