Prokaryotic diversity in one of the largest hypersaline coastal lagoons in the world

Abstract

Araruama Lagoon is an environment characterized by high salt concentrations. The low raining and high evaporation rates in this region favored the development of many salty ponds around the lagoon. In order to reveal the microbial composition of this system, we performed a 16S rRNA gene survey. Among archaea, most clones were related to uncultured environmental Euryarchaeota. In lagoon water, we found some clones related to Methanomicrobia and Methanothermococcus groups, while in the saline pond water members related to the genus Haloarcula were detected. Bacterial community was dominated by clones related to Gamma-proteobacteria, Actinobacteria, and Synechococcus in lagoon water, while Salinibacter ruber relatives dominated in saline pond. We also detected the presence of Alpha-proteobacteria, Pseudomonas-like bacteria and Verrucomicrobia. Only representatives of the genus Ralstonia were cosmopolitan, being observed in both systems. The detection of a substantial number of clones related to uncultured archaea and bacteria suggest that the hypersaline waters of Araruama harbor a pool of novel prokaryotic phylotypes, distinct from those observed in other similar systems. We also observed clones related to halophilic genera of cyanobacteria that are specific for each habitat studied. Additionally, two bacterioplankton molecular markers with ecological relevance were analyzed, one is linked to nitrogen fixation (nifH) and the other is linked to carbon fixation by bacterial photosynthesis, the protochlorophyllide genes, revealing a specific genetic distribution in this ecosystem. This is the first study of the biogeography and community structure of microbial assemblages in Brazilian tropical hypersaline environments. This work is directed towards a better understanding of the free-living prokaryotic diversity adapted to life in hypersaline waters.

Brazilian research on extremophiles in the context of astrobiology

“…Interestingly, the lagoon water and the surrounding saline pond water harbour different Archaea and Bacteria groups. Moreover, culture-independent methods revealed a significant number of clones related to uncultured Archaea and Bacteria suggesting that the Araruama lagoon contain novel micro-organisms, distinct from those observed in other similar hypersaline environments (Clementino et al 2008).…”

Archaea in Natural and Impacted Brazilian Environments

“…As expected, the authors found a great dominance of halophilic euryarchaeotes in their samples and a small number of crenarchaeotes associated with lineages found in marine vents. Curiously, in one of the samples, the halophilic sequences formed a distinct clade, suggesting the presence of new, undescribed, organisms in these waters [39, 40]. …”

Manantiales salinos: Inventarios de Diversidad Metabólica y filogenética de microorganismos de ambientes salinos

“…Nuestros resultados sugieren que en la comunidad microbiana de los tres manantiales predominan más los organismos del dominio Bacteria que los del dominio Archaea, lo cual se ha reportado en ambientes con salinidad de hasta 16 % (p/v) (Dong, et al, 2006;Perreault, et al, 2007;Clementino, et al, 2008); por otra parte, Swan, et al (2010) encontraron que en ambientes moderadamente hipersalinos (5 % (p/v) los organismos del dominio Archaea eran más que los del dominio Bacteria. Con respecto a la predominancia de Bacteria sobre Archaea, se ha discutido la razón de que en un mismo ambiente se tienda a encontrar menor diversidad en Archaea que en Bacteria, pese a que las arqueas contribuyen en gran proporción al total de los filotipos procariotas presentes en la mayoría de los ambientes en los que se han estudiado organismos de ambos dominios (Aller & Kemp, 2008).…”