title: Molecular Assessment of Bacterial Community Dynamics and Functional End Points during Sediment Bioaccumulation Tests.
abstract: Whole sediment toxicity tests play an important role in environmental risk assessment of organic chemicals. It is not clear, however, to what extent changing microbial community composition and associated functions affect sediment test results. We assessed the development of bacterial communities in artificial sediment during a 28 day bioaccumulation test with polychlorinated biphenyls, chlorpyrifos, and four marine benthic invertebrates. DGGE and 454-pyrosequencing of PCR-amplified 16S rRNA genes were used to characterize bacterial community composition. Abundance of total bacteria and selected genes encoding enzymes involved in important microbially mediated ecosystem functions were measured by qPCR. Community composition and diversity responded most to the time course of the experiment, whereas organic matter (OM) content showed a low but significant effect on community composition, biodiversity and two functional genes tested. Moreover, OM content had a higher influence on bacterial community composition than invertebrate species. Medium OM content led to the highest gene abundance and is preferred for standard testing. Our results also indicated that a pre-equilibration period is essential for growth and stabilization of the bacterial community. The observed changes in microbial community composition and functional gene abundance may imply actual changes in such functions during tests, with consequences for exposure and toxicity assessment.
authors.affiliation: Aquatic Ecology and Water Quality Management Group, Wageningen University , P.O Box 47, 6700 AA, Wageningen, The Netherlands.
authors.forename: Noël J
authors.initials: NJ
authors.lastname: Diepens
authors.affiliation: Aquatic Ecology and Water Quality Management Group, Wageningen University , P.O Box 47, 6700 AA, Wageningen, The Netherlands.|Laboratory of Microbiology, Wageningen University , Dreijenplein 10, 6703 HB Wageningen, The Netherlands.
authors.forename: Mauricio R
authors.initials: MR
authors.lastname: Dimitrov
authors.affiliation: Aquatic Ecology and Water Quality Management Group, Wageningen University , P.O Box 47, 6700 AA, Wageningen, The Netherlands.|IMARES, Institute for Marine Resources & Ecosystem Studies, Wageningen UR , P.O. Box 68, 1970 AB IJmuiden, The Netherlands.
authors.forename: Albert A
authors.initials: AA
authors.lastname: Koelmans
authors.affiliation: Laboratory of Microbiology, Wageningen University , Dreijenplein 10, 6703 HB Wageningen, The Netherlands.
authors.forename: Hauke
authors.initials: H
authors.lastname: Smidt
mesh_terms: D000818:Animals; D001419:Bacteria / Q000235:genetics*; D044822:Biodiversity; D004390:Chlorpyrifos / Q000493:pharmacokinetics / Q000633:toxicity; D017753:Ecosystem; D054750:Ecotoxicology / Q000379:methods*; D019015:Geologic Sediments / Q000382:microbiology*; D007448:Invertebrates / Q000145:classification / Q000502:physiology; D059013:Microbial Consortia / Q000502:physiology*; D011078:Polychlorinated Biphenyls / Q000493:pharmacokinetics / Q000633:toxicity; D016133:Polymerase Chain Reaction / Q000379:methods; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D014874:Water Pollutants, Chemical / Q000493:pharmacokinetics / Q000633:toxicity*
chemical_list: D012336:RNA, Ribosomal, 16S; D014874:Water Pollutants, Chemical; D011078:Polychlorinated Biphenyls; D004390:Chlorpyrifos