On 27 February 2010, a magnitude M w = 8.8 earthquake occurred off the coast of Chile's Maule region causing substantial damage and loss of life. Ancestral tsunami knowledge from the 1960 event combined with education and evacuation exercises prompted most coastal residents to spontaneously evacuate after the earthquake. Many of the tsunami victims were tourists in coastal campgrounds. The international tsunami survey team (ITST) was deployed within days of the event and surveyed 800 km of coastline from Quintero to Mehuín and the Pacific Islands of Santa María, Mocha, Juan Fernández Archipelago, and Rapa Nui (Easter). The collected survey data include more than 400 tsunami flow depth, runup and coastal uplift measurements. The tsunami peaked with a localized runup of 29 m on a coastal bluff at Constitución. The observed runup distributions exhibit significant variations on local and regional scales. Observations from the 2010 and 1960 Chile tsunamis are compared.

In this paper, we report the presence of sedimentary microbial ecosystems in wetlands of the Salar de Atacama. These laminated systems, which bind, trap and precipitate mineral include: microbial mats at Laguna Tebenquiche and Laguna La Brava, gypsum domes at Tebenquiche and carbonate microbialites at La Brava. Microbial diversity and key biogeochemical characteristics of both lakes (La Brava and Tebenquiche) and their various microbial ecosystems (non-lithifying mats, flat and domal microbialites) were determined. The composition and abundance of minerals ranged from trapped and bound halite in organic-rich non-lithifying mats to aragonite-dominated lithified flat microbialites and gypsum in lithified domal structures. Pyrosequencing of the V4 region of the 16s rDNA gene showed that Proteobacteria comprised a major phylum in all of the microbial ecosystems studied, with a marked lower abundance in the non-lithifying mats. A higher proportion of Bacteroidetes was present in Tebenquiche sediments compared to La Brava samples. The concentration of pigments, particularly that of Chlorophyll a, was higher in the Tebenquiche than in La Brava. Pigments typically associated with anoxygenic phototrophic bacteria were present in lower amounts. Organic-rich, non-lithifying microbial mats frequently formed snake-like, bulbous structures due to gas accumulation underneath the mat. We hypothesize that the lithified microbialites might have developed from these snake-like microbial mats following mineral precipitation in the surface layer, producing domes with endoevaporitic communities in Tebenquiche and carbonate platforms in La Brava. Whereas the potential role of microbes in carbonate platforms is well established, the contribution of endoevaporitic microbes to formation of gypsum domes needs further investigation.

The Central Andes in northern Chile contains a large number of closed basins whose central depression is occupied by saline lakes and salt crusts (salars). One of these basins is Salar de Llamara (850 m a.s.l.), where large domed structures of seemingly evaporitic origin forming domes can be found. In this work, we performed a detailed microbial characterization of these domes. Mineralogical studies revealed gypsum (CaSO(4)) as a major component. Microbial communities associated to these structures were analysed by 454 16S rDNA amplicon sequencing and compared between winter and summer seasons. Bacteroidetes Proteobacteria and Planctomycetes remained as the main phylogenetic groups, an increased diversity was found in winter. Comparison of the upper air-exposed part and the lower water-submerged part of the domes in both seasons showed little variation in the upper zone, showing a predominance of Chromatiales (Gammaproteobacteria), Rhodospirillales (Alphaproteobacteria), and Sphingobacteriales (Bacteroidetes). However, the submerged part showed marked differences between seasons, being dominated by Proteobacteria (Alpha and Gamma) and Verrucomicrobia in summer, but with more diverse phyla found in winter. Even though not abundant by sequence, Cyanobacteria were visually identified by scanning electron microscopy (SEM), which also revealed the presence of diatoms. Photosynthetic pigments were detected by high-performance liquid chromatography, being more diverse on the upper photosynthetic layer. Finally, the system was compared with other endoevaporite, mats microbialite and Stromatolites microbial ecosystems, showing higher similitude with evaporitic ecosystems from Atacama and Guerrero Negro. This environment is of special interest for extremophile studies because microbial life develops associated to minerals in the driest desert all over the world. Nevertheless, it is endangered by mining activity associated to copper and lithium extraction; thus, its environmental protection preservation is strongly encouraged.

We combined nucleic acid-based molecular methods, biogeochemical measurements, and physicochemical characteristics to investigate microbial sedimentary ecosystems of Laguna Tebenquiche, Atacama Desert, Chile. Molecular diversity, and biogeochemistry of hypersaline microbial mats, rhizome-associated concretions, and an endoevaporite were compared with: The V4 hypervariable region of the 16S rRNA gene was amplified by pyrosequencing to analyze the total microbial diversity (i.e., bacteria and archaea) in bulk samples, and in addition, in detail on a millimeter scale in one microbial mat and in one evaporite. Archaea were more abundant than bacteria. Euryarchaeota was one of the most abundant phyla in all samples, and particularly dominant (97% of total diversity) in the most lithified ecosystem, the evaporite. Most of the euryarchaeal OTUs could be assigned to the class Halobacteria or anaerobic and methanogenic archaea. Planctomycetes potentially also play a key role in mats and rhizome-associated concretions, notably the aerobic organoheterotroph members of the class Phycisphaerae. In addition to cyanobacteria, members of Chromatiales and possibly the candidate family Chlorotrichaceae contributed to photosynthetic carbon fixation. Other abundant uncultured taxa such as the candidate division MSBL1, the uncultured MBGB, and the phylum Acetothermia potentially play an important metabolic role in these ecosystems. Lithifying microbial mats contained calcium carbonate precipitates, whereas endoevoporites consisted of gypsum, and halite. Biogeochemical measurements revealed that based on depth profiles of O2 and sulfide, metabolic activities were much higher in the non-lithifying mat (peaking in the least lithified systems) than in lithifying mats with the lowest activity in endoevaporites. This trend in decreasing microbial activity reflects the increase in salinity, which may play an important role in the biodiversity.

The Atacama Desert has extreme environmental conditions that allow the development of unique microbial communities. The present paper reports the bacterial diversity of microbial mats and sediments and its mineralogical components. Some physicochemical conditions of the water surrounding these ecosystems have also been studied trying to determine their influence on the diversity of these communities. In that way, mats and sediments distributed among different hypersaline lakes located in salt flats of the Atacama Desert were subjected to massive parallel sequencing of the V4 region of the 16S rRNA genes of Bacteria. A higher diversity in sediment than in mat samples have been found. Lakes that harbor microbial mats have higher salinity than lakes where mats are absent. Proteobacteria and/or Bacteroidetes are the major phyla represented in all samples. An interesting item is the finding of a low proportion or absence of Cyanobacteria sequences in the ecosystems studied, suggesting the possibility that other groups may be playing an essential role as primary producers in these extreme environments. Additionally, the large proportion of 16S rRNA gene sequences that could not be classified at the level of phylum indicates potential new phyla present in these ecosystems.

Soybean, Glycine max (L.) Merrill, is one of the most important food crops in the world. High soybean yields require large amounts of N fertilizers, which are expensive and can cause environmental problems. The industrial fixation of nitrogen accounts for about 50% of fossil fuel usage in agriculture. In contrast, biological fixation of N 2 is a low-cost source of N for soybean cropping through the symbiotic association between the plant and soil bacteria belonging to the genera Bradyrhizobium and Sinorhizobium, which are collectively called "soybean rhizobia". In general, symbiotic nitrogen fixation in crop legumes not only reduces fertilizer costs but also improves soil fertility through crop rotation and intercropping. Biological nitrogen fixation is due to symbioses between leguminous plants and species of Rhizobium bacteria. Replacing this natural N source by synthetic N fertilizers would cost around 10 billion dollars annually. Moreover, legume seed and foliage have a higher protein content than that of non-legumes, and this makes them desirable protein crops. There is a wide knowledge of the industrial elaboration and use of commercial soybean inoculants based on bradyrhizobia strains. At present, the technology to prepare different types of inoculants, either solid or liquid, is sufficiently developed to meet market requirements, although further research and investments are still required to improve the symbiotic efficacy of rhizobial inoculants. Inoculation of soybeans under field conditions has been successful in the USA, Brazil and Argentina, which are the world leaders in soybean cultivation in terms of acreage and grain yields. There are, however, limitations to a wider use of rhizobial inoculants: the size of indigenous soil rhizobial populations can prevent the successful use of inoculants in some particular areas. For example, many Chinese soils contain more than 10 5 soybean rhizobia per gram of soil, which imposes a serious barrier for nodule occupancy by the soybean rhizobia used as an inoculant. The use of inoculants based on soil bacteria other than rhizobia has also increased in the last decades. An example is the genus Azospirillum, which can be used for its capacity to increase plant growth and seed yields through different mechanisms, such as the production of plant hormones and the increase in phosphate uptake by roots. In addition, co-inoculation with Azospirillum and rhizobia enhances nodulation and nitrogen fixation. Although less developed, it is expected that inoculants based on mycorrhizal fungi will also play a relevant role in sustainable agriculture and forestry. In spite of any possible limitations, the use of inoculants appears compulsory in a frame of sustainable agriculture, which seeks to increase crop yields and nutrient-use efficiency while reducing the environmental costs associated with agriculture intensification. This review also summarizes some of the most relevant genetic aspects of soybean rhizobia in relation to their symbiosis with soybeans. They can be listed a...

Benthic microbial ecosystems of Laguna La Brava, Salar de Atacama, a high altitude hypersaline lake, were characterized in terms of bacterial and archaeal diversity, biogeochemistry, (including O2 and sulfide depth profiles and mineralogy), and physicochemical characteristics. La Brava is one of several lakes in the Salar de Atacama where microbial communities are growing in extreme conditions, including high salinity, high solar insolation, and high levels of metals such as lithium, arsenic, magnesium, and calcium. Evaporation creates hypersaline conditions in these lakes and mineral precipitation is a characteristic geomicrobiological feature of these benthic ecosystems. In this study, the La Brava non-lithifying microbial mats, microbialites, and rhizome-associated concretions were compared to each other and their diversity was related to their environmental conditions. All the ecosystems revealed an unusual community where Euryarchaeota, Crenarchaeota, Acetothermia, Firmicutes and Planctomycetes were the most abundant groups, and cyanobacteria, typically an important primary producer in microbial mats, were relatively insignificant or absent. This suggests that other microorganisms, and possibly novel pathways unique to this system, are responsible for carbon fixation. Depth profiles of O2 and sulfide showed active production and respiration. The mineralogy composition was calcium carbonate (as aragonite) and increased from mats to microbialites and rhizome-associated concretions. Halite was also present. Further analyses were performed on representative microbial mats and microbialites by layer. Different taxonomic compositions were observed in the upper layers, with Archaea dominating the non-lithifying mat, and Planctomycetes the microbialite. The bottom layers were similar, with Euryarchaeota, Crenarchaeota and Planctomycetes as dominant phyla. Sequences related to Cyanobacteria were very scarce. These systems may contain previously uncharacterized community metabolisms, some of which may be contributing to net mineral precipitation. Further work on these sites might reveal novel organisms and metabolisms of biotechnological interest.

Biofilms, microbial mats, and microbialites dwell under highly limiting conditions (high salinity, extreme aridity, pH, and elevated arsenic concentration) in the Andean Puna. Only recent pioneering studies have described the microbial diversity of different Altiplano lakes and revealed their unexpectedly diverse microbial communities. Arsenic metabolism is proposed to be an ancient mechanism to obtain energy by microorganisms. Members of Bacteria and Archaea are able to exploit arsenic as a bioenergetic substrate in either anaerobic arsenate respiration or chemolithotrophic growth on arsenite. Only six aioAB sequences coding for arsenite oxidase and three arrA sequences coding for arsenate reductase from haloarchaea were previously deposited in the NCBI database. However, no experimental data on their expression and function has been reported. Recently, our working group revealed the prevalence of haloarchaea in a red biofilm from Diamante Lake and microbial mat from Tebenquiche Lake using a metagenomics approach. Also, a surprisingly high abundance of genes used for anaerobic arsenate respiration (arr) and arsenite oxidation (aio) was detected in the Diamante's metagenome. In order to study in depth the role of arsenic in these haloarchaeal communities, in this work, we obtained 18 haloarchaea belonging to the Halorubrum genus, tolerant to arsenic. Furthermore, the identification and expression analysis of genes involved in obtaining energy from arsenic compounds (aio and arr) showed that aio and arr partial genes were detected in 11 isolates, and their expression was verified in two selected strains. Better growth of two isolates was obtained in presence of arsenic compared to control. Moreover, one of the isolates was able to oxidize As[III]. The confirmation of the oxidation of arsenic and the transcriptional expression of these genes by RT-PCR strongly support the hypothesis that the arsenic can be used in bioenergetics processes by the microorganisms flourishing in these environments.