Data from: Contrasting taxonomic stratification of microbial communities in two hypersaline meromictic lakes

Hypersaline meromictic lakes are extreme environments in which water
stratification is associated with powerful physicochemical gradients and
high salt concentrations. Furthermore, their physical stability coupled
with vertical water column partitioning makes them important research
model systems in microbial niche differentiation and biogeochemical
cycling. Here, we compare the prokaryotic assemblages from Ursu and Fara
Fund hypersaline meromictic lakes (Transylvanian Basin, Romania) in
relation to their limnological factors and infer their role in elemental
cycling by matching taxa to known taxon-specific biogeochemical functions.
To assess the composition and structure of prokaryotic communities and the
environmental factors that structure them, deep-coverage small subunit
(SSU) ribosomal RNA (rDNA) amplicon sequencing, community domain-specific
quantitative PCR and physicochemical analyses were performed on samples
collected along depth profiles. The analyses showed that the lakes
harbored multiple and diverse prokaryotic communities whose distribution
mirrored the water stratification patterns. Ursu Lake was found to be
dominated by Bacteria and to have a greater prokaryotic diversity than
Fara Fund Lake that harbored an increased cell density and was populated
mostly by Archaea within oxic strata. In spite of their contrasting
diversity, the microbial populations indigenous to each lake pointed to
similar physiological functions within carbon degradation and sulfate
reduction. Furthermore, the taxonomy results coupled with methane
detection and its stable C isotope composition indicated the presence of a
yet-undescribed methanogenic group in the lakes’ hypersaline
monimolimnion. In addition, ultrasmall uncultivated archaeal lineages were
detected in the chemocline of Fara Fund Lake, where the recently proposed
Nanohaloarchaeota phylum was found to thrive.