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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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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.

objective
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.

2 4 dichlorophenoxyacetic acid 2 4 d
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

techniques used
Techniques used
  • Enumeration
  • Metabolism
techniques used1
Techniques used
  • Enumeration
    • Cultivation:
    • Non-cultivation:
  • Metabolism
    • Degradation:
    • Mineralization:
techniques used2
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)
strengths and weaknesses of techniques
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 ….
slide13

No Pseudomonas on Gould’s but detected with 16S rDNA

Pseudomonas in acclimated sediment

Role of Pseudomonas in degradation? Mineralization study?

slide15

MPN-25% degradation

- RFLP patterns in B2 different from others

- tdf no homology with known sequences

slide16

Restriction endonucleases

Specific recognition sites 4-6 basepairs

slide17

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