title: Crenarchaeota and Euryarchaeota in temperate estuarine sediments.
abstract: OBJECTIVE
  Application of molecular techniques to ecological studies has unveiled a wide diversity of micro-organisms in natural communities, previously unknown to microbial ecologists. New lineages of Archaea were retrieved from several non-extreme environments, showing that these micro-organisms are present in a large variety of ecosystems. The aim was therefore to assess the presence and diversity of Archaea in the sediments of the river Douro estuary (Portugal), relating the results obtained to ecological data.
  
  
  RESULTS
  Total DNA was extracted from sediment samples obtained from an estuary deprived of vegetation, amplified by PCR and the resulting DNA fragments cloned. The archaeal origin of the cloned inserts was checked by Southern blot, dot blot or colony blot hybridization. Recombinant plasmids were further analysed by restriction with AvaII and selected for sequencing. Phylogenetic analyses of 14 sequences revealed the presence of members of the domain Archaea. Most of the sequences could be assigned to the kingdom Crenarchaeota.
  
  
  CONCLUSIONS
  Most of these sequences were closely related to those obtained from non-extreme Crenarchaeota members previously retrieved from diverse ecosystems, such as freshwater and marine environments.
  
  
  CONCLUSIONS
  The presence of archaeal 16S rDNA sequences in temperate estuarine sediments emerges as a valuable contribution to the understanding of the complexity of the ecosystem.
authors.affiliation: Laboratório de Hidrobiologia, Instituto de Ciências Biomédicas de Abel Salazar, Porto, Portugal. crigaud@icbas.up.pt
authors.forename: C
authors.initials: C
authors.lastname: Abreu
authors.forename: G
authors.initials: G
authors.lastname: Jurgens
authors.forename: P
authors.initials: P
authors.lastname: De Marco
authors.forename: A
authors.initials: A
authors.lastname: Saano
authors.forename: A A
authors.initials: AA
authors.lastname: Bordalo
mesh_terms: D003001:Cloning, Molecular; D019615:Crenarchaeota / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D019641:DNA, Archaeal / Q000235:genetics; D019605:Euryarchaeota / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D019015:Geologic Sediments / Q000382:microbiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011174:Portugal; D019642:RNA, Archaeal / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D014871:Water Microbiology
chemical_list: D019641:DNA, Archaeal; D019642:RNA, Archaeal; D012336:RNA, Ribosomal, 16S