title: Microeukaryote diversity in a marine methanol-fed fluidized denitrification system.
abstract: The marine methanol-fed fluidized denitrification system operated by the Montreal Biodome includes carriers on which a denitrifying biofilm has developed. Previous observations showed a high abundance of microeukaryotes living in and around the biofilm. These eukaryotes may influence the system's denitrification efficiency. The composition of the microeukaryote population was determined. Microscopic observations showed at least 20 different morphologies that included large numbers of ciliates. Molecular analyses of an 18S ribosomal RNA (rDNA) gene library revealed 31 different phylotypes. Alveolobiontes were the most abundant phylotypes and made up 75% of the 159 screened clones. Other eukaryotic groups, including Stramenopiles, Fungi, Amoebozoa, and nematodes, were also present. From 18S rDNA specific sequences, one of the Amoebozoa-affiliated phylotypes was visualized by fluorescence in situ hybridization. It had a rod-like irregular shape and measured less than 5 mum in length. We determined the impact of protozoans on the denitrifying activity. In a laboratory-scale batch culture assays, the denitrifying biofilm was treated with cycloheximide and nystatin that eliminated the protozoans. No difference in the denitrification rate was found. However, planktonic bacteria were more abundant in the treated culture medium.
authors.affiliation: INRS-Institut Armand-Frappier, 531 boulevard des Prairies, Laval, Quebec, Canada H7V 1B7.
authors.forename: Véronique
authors.initials: V
authors.lastname: Laurin
authors.forename: Normand
authors.initials: N
authors.lastname: Labbé
authors.forename: Serge
authors.initials: S
authors.lastname: Parent
authors.forename: Pierre
authors.initials: P
authors.lastname: Juteau
authors.forename: Richard
authors.initials: R
authors.lastname: Villemur
mesh_terms: D016841:Amoebida / Q000145:classification / Q000235:genetics / Q000254:growth & development*; D000818:Animals; D044822:Biodiversity; D018441:Biofilms / Q000254:growth & development; D056890:Eukaryota / Q000145:classification / Q000235:genetics / Q000254:growth & development*; D005658:Fungi / Q000145:classification / Q000235:genetics / Q000254:growth & development*; D017404:In Situ Hybridization, Fluorescence; D000432:Methanol / Q000378:metabolism*; D009348:Nematoda / Q000145:classification / Q000235:genetics / Q000254:growth & development*; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012623:Seawater / Q000382:microbiology / Q000469:parasitology
chemical_list: D012337:RNA, Ribosomal, 18S; D000432:Methanol