The structure of the
Bacteria and
Archaea community in a large drinking water reservoir (Marathonas, Greece; MR) was investigated in October 2007 and September 2008, using 16S rRNA gene clone libraries. The bacterial communities were more diverse than archaeal communities (Shannon diversity index
H’ 0.81-3.28 and 1.36-1.77, respectively). The overall bacterial community composition was comparable to bacterioplankton community described in other freshwater habitats. Within the
Bacteria,
Betaproteobacteria dominated, while representatives of
Alpha-,
Gamma- and
Deltaproteobacteria also occurred. Other important phyla were
Actinobacteria and
Bacteroidetes, while representatives of
Acidobacteria,
Cyanobacteria,
Chloroflexi,
Planctomycetes and
Verrucomicrobia were also retrieved. Several phylotypes in
Alpha- and
Betaproteobacteria and
Bacteroidetes were related to bacteria capable of cyanotoxin degradation and with aromatic compounds/iron oxidizers or polymer degraders.
Euryarchaeota dominated (60.5%) the
Archaea community mostly with phylotypes related to
Methanobacteriales and
Methanosarcinales. Among the
Thaumarchaeota, the two most abundant phylotypes were affiliated (97% similarity) with the only cultivated mesophilic thaumarchaeote of marine origin,
Nitrosopumilus maritimus. Temporal and spatial comparison of the prokaryotic community structure revealed that three of the most abundant prokaryotic phylotypes, belonging to
Actinobacteria, were recovered from all sites both years, suggesting that these
Actinobacteria could be important key players in MR ecosystem functioning.
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