Phylogenetic Analysis of a Microbialite-Forming Microbial Mat From a Hypersaline Lake of the Kiritimati Atoll, Central Pacific

PLoS One. 2013 Jun 10;8(6):e66662. doi: 10.1371/journal.pone.0066662. Print 2013.

Abstract

On the Kiritimati atoll, several lakes exhibit microbial mat-formation under different hydrochemical conditions. Some of these lakes trigger microbialite formation such as Lake 21, which is an evaporitic, hypersaline lake (salinity of approximately 170‰). Lake 21 is completely covered with a thick multilayered microbial mat. This mat is associated with the formation of decimeter-thick highly porous microbialites, which are composed of aragonite and gypsum crystals. We assessed the bacterial and archaeal community composition and its alteration along the vertical stratification by large-scale analysis of 16S rRNA gene sequences of the nine different mat layers. The surface layers are dominated by aerobic, phototrophic, and halotolerant microbes. The bacterial community of these layers harbored Cyanobacteria (Halothece cluster), which were accompanied with known phototrophic members of the Bacteroidetes and Alphaproteobacteria. In deeper anaerobic layers more diverse communities than in the upper layers were present. The deeper layers were dominated by Spirochaetes, sulfate-reducing bacteria (Deltaproteobacteria), Chloroflexi (Anaerolineae and Caldilineae), purple non-sulfur bacteria (Alphaproteobacteria), purple sulfur bacteria (Chromatiales), anaerobic Bacteroidetes (Marinilabiacae), Nitrospirae (OPB95), Planctomycetes and several candidate divisions. The archaeal community, including numerous uncultured taxonomic lineages, generally changed from Euryarchaeota (mainly Halobacteria and Thermoplasmata) to uncultured members of the Thaumarchaeota (mainly Marine Benthic Group B) with increasing depth.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Archaea / classification
  • Archaea / genetics*
  • Bacteria / classification
  • Bacteria / genetics*
  • Biodiversity
  • DNA, Archaeal / genetics
  • DNA, Bacterial / genetics
  • Geologic Sediments / analysis*
  • Lakes
  • Phylogeny*
  • RNA, Ribosomal, 16S / genetics*
  • Real-Time Polymerase Chain Reaction
  • Salinity*
  • Sequence Analysis, DNA

Substances

  • DNA, Archaeal
  • DNA, Bacterial
  • RNA, Ribosomal, 16S

Grant support

This study has been supported by the Deutsche Forschungsgemeinschaft (DFG-FOR 571 “Geobiology of Organo- and Biofilms”; DA 374/5-2, AR335/5-3, publication 61) and the Courant Center Geobiology. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.