title: Comparing metabolic functionalities, community structures, and dynamics of herbicide-degrading communities cultivated with different substrate concentrations.
abstract: Two 4-chloro-2-methylphenoxyacetic acid (MCPA)-degrading enrichment cultures selected from an aquifer on low (0.1 mg liter(-1)) or high (25 mg liter(-1)) MCPA concentrations were compared in terms of metabolic activity, community composition, population growth, and single cell physiology. Different community compositions and major shifts in community structure following exposure to different MCPA concentrations were observed using both 16S rRNA gene denaturing gradient gel electrophoresis fingerprinting and pyrosequencing. The communities also differed in their MCPA-mineralizing activities. The enrichments selected on low concentrations mineralized MCPA with shorter lag phases than those selected on high concentrations. Flow cytometry measurements revealed that mineralization led to cell growth. The presence of low-nucleic acid-content bacteria (LNA bacteria) was correlated with mineralization activity in cultures selected on low herbicide concentrations. This suggests that LNA bacteria may play a role in degradation of low herbicide concentrations in aquifers impacted by agriculture. This study shows that subpopulations of herbicide-degrading bacteria that are adapted to different pesticide concentrations can coexist in the same environment and that using a low herbicide concentration enables enrichment of apparently oligotrophic subpopulations.
authors.affiliation: Department of Geochemistry, Geological Survey of Denmark and Greenland, Copenhagen K, Denmark.
authors.forename: Erkin
authors.initials: E
authors.lastname: Gözdereliler
authors.forename: Nico
authors.initials: N
authors.lastname: Boon
authors.forename: Jens
authors.initials: J
authors.lastname: Aamand
authors.forename: Karen
authors.initials: K
authors.lastname: De Roy
authors.forename: Michael S
authors.initials: MS
authors.lastname: Granitsiotis
authors.forename: Hans-Jørgen
authors.initials: HJ
authors.lastname: Albrechtsen
authors.forename: Sebastian R
authors.initials: SR
authors.lastname: Sørensen
mesh_terms: D008456:2-Methyl-4-chlorophenoxyacetic Acid / Q000378:metabolism*; D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D058448:Biota; D058645:Denaturing Gradient Gel Electrophoresis; D005434:Flow Cytometry; D060587:Groundwater / Q000382:microbiology*; D006540:Herbicides / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D006540:Herbicides; D012336:RNA, Ribosomal, 16S; D008456:2-Methyl-4-chlorophenoxyacetic Acid