Publication Date:
2021-04-25
Description:
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.
Keywords:
Phylogenetic Analysis; Microbialite; Microbial Mat; Hypersaline Lake; Kiritimati Atoll
;
551
Language:
English
Type:
article
,
publishedVersion
Format:
14
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