12 research outputs found
Speciation and ecological success in dimly lit waters: horizontal gene transfer in a green sulfur bacteria bloom unveiled by metagenomic assembly
11 páginas, 6 figuras.A natural planktonic bloom of a brown-pigmented photosynthetic green sulfur bacteria (GSB) from the
disphotic zone of karstic Lake Banyoles (NE Spain) was studied as a natural enrichment culture from
which a nearly complete genome was obtained after metagenomic assembly. We showed in situ a case
where horizontal gene transfer (HGT) explained the ecological success of a natural population unveiling
ecosystem-specific adaptations. The uncultured brown-pigmented GSB was 99.7% identical in the 16S
rRNA gene sequence to its green-pigmented cultured counterpart Chlorobium luteolum DSM 273T.
Several differences were detected for ferrous iron acquisition potential, ATP synthesis and gas vesicle
formation, although the most striking trait was related to pigment biosynthesis strategy. Chl. luteolum
DSM 273T synthesizes bacteriochlorophyll (BChl) c, whereas Chl. luteolum CIII incorporated by HGT a
18-kbp cluster with the genes needed for BChl e and specific carotenoids biosynthesis that provided
ecophysiological advantages to successfully colonize the dimly lit waters. We also genomically
characterized what we believe to be the first described GSB phage, which based on the metagenomic
coverage was likely in an active state of lytic infection. Overall, we observed spread HGT and we
unveiled clear evidence for virus-mediated HGT in a natural population of photosynthetic GSB.This research was funded by grant DARKNESS CGL2012-
32747 from the Spanish Office of Science (MINECO) to
EOC and by the Global Ocean Sampling Project supported
by the Beyster Family Foundation Fund of the San Diego
Foundation and the Life Technology Foundation (to JCVI).
Work on BChl e biosynthesis and the genomics of GSB in
the laboratory of DAB was supported by the Division of
Chemical Sciences, Geosciences, and Biosciences, Office
of Basic Energy Sciences of the U.S. Department of Energy
through Grant DE-FG02-94ER20137.Peer reviewe
Vertical segregation and phylogenetic characterization of ammonia-oxidizing Archaea in a deep oligotrophic lake
12 páginas, 6 figuras, 1 tabla.Freshwater habitats have been identified as one of the largest reservoirs of archaeal genetic diversity, with specific lineages of ammonia-oxidizing archaea (AOA) populations different from soils and seas. The ecology and biology of lacustrine AOA is, however, poorly known. In the present study, vertical changes in archaeal abundance by CARD-FISH, quantitative PCR (qPCR) analyses and identity by clone libraries were correlated with environmental parameters in the deep glacial high-altitude Lake Redon. The lake is located in the central Spanish Pyrenees where atmospheric depositions are the main source of reactive nitrogen. Strong correlations were found between abundance of thaumarchaeotal 16S rRNA gene, archaeal amoA gene and nitrite concentrations, indicating an ammonium oxidation potential by these microorganisms. The bacterial amoA gene was not detected. Three depths with potential ammonia-oxidation activity were unveiled along the vertical gradient, (i) on the top of the lake in winter–spring (that is, the 0 oC slush layers above the ice-covered sheet), (ii) at the thermocline and (iii) the bottom waters in summer—autumn. Overall, up to 90% of the 16S rRNA gene sequences matched Thaumarchaeota, mostly from both the Marine Group (MG) 1.1a (Nitrosoarchaeum-like) and the sister clade SAGMGC−1 (Nitrosotalea-like). Clone-libraries analysis showed the two clades changed their relative abundances with water depth being higher in surface and lower in depth for SAGMGC−1 than for MG 1.1a, reflecting a vertical phylogenetic segregation. Overall, the relative abundance and recurrent appearance of SAGMGC−1 suggests a significant environmental role of this clade in alpine lakes. These results expand the set of ecological and thermal conditions where Thaumarchaeota are distributed, unveiling vertical positioning in the water column as a key factor to understand the ecology of different thaumarchaeotal clades in lacustrine environments.This research was
supported by grants CRENYC CGL2006-12058 and PIRENA
CGL2009-13318 to EOC, and CONSOLIDER grant GRACCIE
CSD2007-00067 from the Spanish Office of Science and
Innovation (MICINN). JCA benefits from a Juan de la Cierva
postdoctoral fellow (MICINN).Peer reviewe