Distribution and diversity of archaea corresponding to the limnological cycle of a hypersaline stratified lake (Solar Lake, Sinai, Egypt)

The vertical and seasonal distribution and diversity of archaeal sequences was investigated in a hypersaline, stratified, monomictic lake, Solar Lake, Sinai, Egypt, during the limnological development of stratification and mi xing, Archaeal sequences were studied via phylogenetic analysis of 16S rDNA sequences as well as denaturing gradient gel electrophoresis analysis. The 165 clones studied were grouped into four phylogenetically different clust ers, Most of the clones isolated from both the aerobic epilimnion and the s ulfide-rich hypolimnion were defined as cluster I, belonging to the Halobac teriaceae family, The three additional clusters were all isolated from the anaerobic hypolimnion. Cluster II is phylogenetically located between the g enera il Methanobacterium and Methanococcus, Clusters III and TV relate to two previously documented groups of uncultured euryarchaeota, remotely rela ted to the genus Thermoplasma. No crenarchaeota were found in the water col umn of the Solar Lake. The archaeal community in the Solar Lake under both stratified and mixed conditions was dominated by halobacteria in salinities higher than 10%. During stratification, additional clusters, some of which may possibly relate to uncultured halophilic methanogens, were found in th e sulfide- and methane-rich hypolimnion.