1 research outputs found
High Bacterial Diversity in Epilithic Biofilms of Oligotrophic Mountain Lakes
10 páginas, 6 figuras, 1 tabla.Benthic microbial biofilms attached to rocks (epilithic) are major sites of carbon cycling and can dominate
ecosystem primary production in oligotrophic lakes. We studied the bacterial community composition of littoral epilithic
biofilms in five connected oligotrophic high mountain lakes
located at different altitudes by genetic fingerprinting and
clone libraries of the 16S rRNA gene. Different intra-lake
samples were analyzed, and consistent changes in community
structure (chlorophyll a and organic matter contents, and
bacterial community composition) were observed along the
altitudinal gradient, particularly related with the location of the
lake above or below the treeline. Epilithic biofilm genetic
fingerprints were both more diverse among lakes than within
lakes and significantly different between montane (below the
tree line) and alpine lakes (above the tree line). The genetic
richness in the epilithic biofilm was much higher than in the
plankton of the same lacustrine area studied in previous
works, with significantly idiosyncratic phylogenetic composition (specifically distinct from lake plankton or mountain
soils). Data suggest the coexistence of aerobic, anaerobic,
phototrophic, and chemotrophic microorganisms in the
biofilm, Bacteroidetes and Cyanobacteria being the most important bacterial taxa, followed by Alpha-, Beta-, Gamma-,
and Deltaproteobacteria, Chlorobi, Planctomycetes, and Verrucomicrobia. The degree of novelty was especially high for
epilithic Bacteroidetes, and up to 50 % of the sequences
formed monophyletic clusters distantly related to any previously reported sequence. More than 35 % of the total sequences matched at <95 % identity to any previously reported 16S
rRNA gene, indicating that alpine epilithic biofilms are unexplored habitats that contain a substantial degree of novelty
within a short geographical distance. Further research is needed to determine whether these communities are involved in
more biogeochemical pathways than previously thought.This research was supported by grants TRAZAS (CGL2004-
02989), NitroPir (CGL2010-19373), and PIRENA (CGL2009-13318)
from the Spanish Office of Science and Innovation (MICINN), the
CONSOLIDER grant GRACCIE CSD2007-00067 (MICINN), and the
EU Project Euro-Limpacs (GOCE-CT-2003- 505540).Peer reviewe