title: Temporal Dynamics of Active Prokaryotic Nitrifiers and Archaeal Communities from River to Sea.
abstract: To test if different niches for potential nitrifiers exist in estuarine systems, we assessed by pyrosequencing the diversity of archaeal gene transcript markers for taxonomy (16S ribosomal RNA (rRNA)) during an entire year along a salinity gradient in surface waters of the Charente estuary (Atlantic coast, France). We further investigated the potential for estuarine prokaryotes to oxidize ammonia and hydrolyze urea by quantifying thaumarchaeal amoA and ureC and bacterial amoA transcripts. Our results showed a succession of different nitrifiers from river to sea with bacterial amoA transcripts dominating in the freshwater station while archaeal transcripts were predominant in the marine station. The 16S rRNA sequence analysis revealed that Thaumarchaeota marine group I (MGI) were the most abundant overall but other archaeal groups like Methanosaeta were also potentially active in winter (December-March) and Euryarchaeota marine group II (MGII) were dominant in seawater in summer (April-August). Each station also contained different Thaumarchaeota MGI phylogenetic clusters, and the clusters' microdiversity was associated to specific environmental conditions suggesting the presence of ecotypes adapted to distinct ecological niches. The amoA and ureC transcript dynamics further indicated that some of the Thaumarchaeota MGI subclusters were involved in ammonia oxidation through the hydrolysis of urea. Our findings show that ammonia-oxidizing Archaea and Bacteria were adapted to contrasted conditions and that the Thaumarchaeota MGI diversity probably corresponds to distinct metabolisms or life strategies.
authors: Laboratoire "Microorganismes: Génome et Environnement", Clermont Université, Université Blaise Pascal, BP 10448, 63000, Clermont-Ferrand, France.
authors: Mylène
authors: M
authors: Hugoni
authors: Hélène
authors: H
authors: Agogué
authors: Najwa
authors: N
authors: Taib
authors: Isabelle
authors: I
authors: Domaizon
authors: Anne
authors: A
authors: Moné
authors: Pierre E
authors: PE
authors: Galand
authors: Gisèle
authors: G
authors: Bronner
authors: Didier
authors: D
authors: Debroas
authors: Isabelle
authors: I
authors: Mary
mesh_terms: D001105:Archaea / Q000145:classification / Q000235:genetics*; D001419:Bacteria / Q000145:classification / Q000235:genetics; D004275:DNA, Ribosomal; D063366:Estuaries; D005618:Fresh Water / Q000382:microbiology; D010802:Phylogeny; D045483:Rivers / Q000382:microbiology; D012623:Seawater / Q000382:microbiology
chemical_list: D004275:DNA, Ribosomal