title: Detection and localization of syntrophic propionate-oxidizing bacteria in granular sludge by in situ hybridization using 16S rRNA-based oligonucleotide probes.
abstract: In situ hybridization with fluorescent oligonucleotides was used to detect and localize microorganisms in the granules of two lab-scale upflow anaerobic sludge blanket reactors that had been fed for several months with either sucrose or a mixture of volatile fatty acids. Sections of the granules were hybridized with 16S rRNA-targeted oligonucleotide probes for Bacteria, Archaea, specific phylogenetic groups of methanogens, and two syntrophic propionate-oxidizing strains, MPOB and KOPROP1. Cells of the syntrophic strain KOPROP1 were not detected in either type of sludge granules. Hybridizations of the sucrose-fed granules showed an outer layer of mainly bacterial microcolonies with different morphologies. More inwards of these granules, a layer of different methanogenic microcolonies mixed with large colonies of the syntrophic strain MPOB could be detected. The MPOB colonies were intertwined with hydrogen- or formate-consuming methanogens, indicating their syntrophic growth. The granules fed with volatile fatty acids showed an outer layer of mainly bacteria and then a thick layer of Methanosaeta-like methanogens mixed with a few bacteria and a layer of methanogens mixed with syntrophic MPOB microcolonies. The centers of both sludge types consisted of large cavities and methanogenic microcolonies. These results indicate a juxtapositioning of syntrophic bacteria and methanogens and provide additional evidence for a layered microbial architecture of anaerobic granular sludge.
authors.affiliation: Department of Microbiology, Wageningen Agricultural University, The Netherlands.
authors.forename: H J
authors.initials: HJ
authors.lastname: Harmsen
authors.forename: H M
authors.initials: HM
authors.lastname: Kengen
authors.forename: A D
authors.initials: AD
authors.lastname: Akkermans
authors.forename: A J
authors.initials: AJ
authors.lastname: Stams
authors.forename: W M
authors.initials: WM
authors.lastname: de Vos
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D001483:Base Sequence; D004783:Environmental Microbiology; D017404:In Situ Hybridization, Fluorescence; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D010084:Oxidation-Reduction; D011422:Propionates / Q000378:metabolism; D012329:RNA, Bacterial / Q000032:analysis*; D012336:RNA, Ribosomal, 16S / Q000032:analysis*; D012722:Sewage / Q000382:microbiology*
chemical_list: D015345:Oligonucleotide Probes; D011422:Propionates; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012722:Sewage