Microorganisms that thrive in hypersaline environments on the surface of our planet are exposed to the harmful effects of ultraviolet radiation. Therefore, for their protection, they have sunscreen ...pigments and highly efficient DNA repair and protection systems. The present study aimed to identify new genes involved in UV radiation resistance from these microorganisms, many of which cannot be cultured in the laboratory. Thus, a functional metagenomic approach was used and for this, small-insert libraries were constructed with DNA isolated from microorganisms of high-altitude Andean hypersaline lakes in Argentina (Diamante and Ojo Seco lakes, 4,589 and 3,200 m, respectively) and from the Es Trenc solar saltern in Spain. The libraries were hosted in a UV radiation-sensitive strain of
(
mutant) and they were exposed to UVB. The resistant colonies were analyzed and as a result, four clones were identified with environmental DNA fragments containing five genes that conferred resistance to UV radiation in
. One gene encoded a RecA-like protein, complementing the mutation in
that makes the
host strain more sensitive to UV radiation. Two other genes from the same DNA fragment encoded a TATA-box binding protein and an unknown protein, both responsible for UV resistance. Interestingly, two other genes from different and remote environments, the Ojo Seco Andean lake and the Es Trenc saltern, encoded two hypothetical proteins that can be considered homologous based on their significant amino acid similarity (49%). All of these genes also conferred resistance to 4-nitroquinoline 1-oxide (4-NQO), a compound that mimics the effect of UV radiation on DNA, and also to perchlorate, a powerful oxidant that can induce DNA damage. Furthermore, the hypothetical protein from the Es Trenc salterns was localized as discrete foci possibly associated with damaged sites in the DNA in cells treated with 4-NQO, so it could be involved in the repair of damaged DNA. In summary, novel genes involved in resistance to UV radiation, 4-NQO and perchlorate have been identified in this work and two of them encoding hypothetical proteins that could be involved in DNA damage repair activities not previously described.
Hypersaline lakes and saltern areas are important industrial and biodiversity resources in the Qaidam Basin of China that reside at > 2600 m asl. Most hypersaline environments in this area are ...characterized by saturated salinity (~ 300 g/L salinity), nearly neutral pH, intense ultraviolet radiation, and extremely variable temperature fluctuations. The core bacterial communities associated with these stressful environments have nevertheless remained uninvestigated. 16S rRNA gene Illumina sequencing analyses revealed that the bacterial communities were dominated by core lineages including the
Proteobacteria
(39.4–64.6%) and the
Firmicutes
(17.0–42.7%). However, the relative abundances of common lineages, and especially the five most abundant taxa of
Pseudomonas
,
Lactococcus
,
Anoxybacillus
,
Acinetobacter
, and
Brevundimonas
, were highly variable across communities and closely associated with hypersaline characteristics in the samples. Network analysis revealed the presence of co-occurrence high relative abundance taxa (cluster I) that were highly correlated across all hypersaline samples. Additionally, temperature, total organic carbon, K
+
, and Mg
2+
correlated highest with taxonomic distributions across communities. These results highlight the potential mechanisms that could underlie survival and adaptation to these extreme hypersaline ecosystems.
Three wetland‐shallow lakes were studied with the aim of analysing the processes and factors that control hydrochemistry and evaporite deposits in them in basins of the Pampean Plain, Argentina. In ...this sense, water balances and analysis of the water content of the lakes with normalized water difference index were made, and geologic‐geomorphological characteristics and groundwater flows were defined. Groundwater, surface water and evaporite samples were taken, along with sediment samples from wetland‐shallow lakes and surroundings. In situ pH, electrical conductivity and temperature, and laboratory chemical determinations of major ions of the water were measured. x‐ray diffraction (XRD) and scanning electron microscope (SEM)‐energy dispersive spectroscopy (EDS) analyses of evaporite and sediment samples were carried out. The results obtained allow the identification of two different systems. One of them is represented by Leubucó wetland‐lake basin, which is topographically higher and smaller than the other system, with Na‐HCO3 and Na‐Cl/SO4 groundwater inflows, with high concentrations of Ca2+ and Mg2+. In periods of high evaporation, the regional water table drops, and due to its topographic position, the lake dries. These determine the formation of thick layers of halite associated with magnesium salts on surface, and gypsum layers interbedded with clastic sediments. The other system involves de la Sal and Chasilauquen wetland‐lake basins, which have larger extensions. They receive Na‐HCO3 and Na‐Cl/SO4 groundwater inflow, but with low Mg2+ and Ca2+. Their lower topographic position determines that even during deficit periods, the water table intercepts the lakes surface and therefore, lakes have a shallow surface water level almost all the year, which is hypersaline, Na‐Cl type. These systems only have thin evaporite crusts, composed of halite and thenardite at the edges of the lakes, and the formation of Ca‐Mg sulfates is not observed. It is concluded that topographic position, basins size, geology, groundwater inflow and evaporation are the main processes and factors controlling hydrochemistry and evaporitic deposits.
Two different systems of hypersaline wetland‐shallow lakes are recognized. Various factors control hydrochemistry and evaporitic deposits in these systems. The chemistry of groundwater discharge determines the types of evaporite salts.
Hypersaline environments represent some of the most challenging settings for life on Earth. Extremely halophilic microorganisms have been selected to colonize and thrive in these extreme environments ...by virtue of a broad spectrum of adaptations to counter high salinity and osmotic stress. Although there is substantial data on microbial taxonomic diversity in these challenging ecosystems and their primary osmoadaptation mechanisms, less is known about how hypersaline environments shape the genomes of microbial inhabitants at the functional level. In this study, we analyzed the microbial communities in five ponds along the discontinuous salinity gradient from brackish to salt-saturated environments and sequenced the metagenome of the salt (halite) precipitation pond in the artisanal Cáhuil Solar Saltern system. We combined field measurements with spectrophotometric pigment analysis and flow cytometry to characterize the microbial ecology of the pond ecosystems, including primary producers and applied metagenomic sequencing for analysis of archaeal and bacterial taxonomic diversity of the salt crystallizer harvest pond. Comparative metagenomic analysis of the Cáhuil salt crystallizer pond against microbial communities from other salt-saturated aquatic environments revealed a dominance of the archaeal genus
and showed an unexpectedly low abundance of
in the Cáhuil system. Functional comparison of 26 hypersaline microbial metagenomes revealed a high proportion of sequences associated with nucleotide excision repair, helicases, replication and restriction-methylation systems in all of them. Moreover, we found distinctive functional signatures between the microbial communities from salt-saturated (>30% w/v total salinity) compared to sub-saturated hypersaline environments mainly due to a higher representation of sequences related to replication, recombination and DNA repair in the former. The current study expands our understanding of the diversity and distribution of halophilic microbial populations inhabiting salt-saturated habitats and the functional attributes that sustain them.
Hypersaline environments encompass aquatic and terrestrial habitats. While only a limited number of studies on the microbial diversity of saline soils have been carried out, hypersaline lakes and ...marine salterns have been thoroughly investigated, resulting in an aquatic-biased knowledge about life in hypersaline environments. To improve our understanding of the assemblage of microbes thriving in saline soils, we assessed the phylogenetic diversity and metabolic potential of the prokaryotic community of two hypersaline soils (with electrical conductivities of ~24 and 55 dS/m) from the Odiel saltmarshes (Spain) by metagenomics. Comparative analysis of these soil databases with available datasets from salterns ponds allowed further identification of unique and shared traits of microbial communities dwelling in these habitats. Saline soils harbored a more diverse prokaryotic community and, in contrast to their aquatic counterparts, contained sequences related to both known halophiles and groups without known halophilic or halotolerant representatives, which reflects the physical heterogeneity of the soil matrix. Our results suggest that
and certain Balneolaeota members may preferentially thrive in aquatic or terrestrial habitats, respectively, while haloarchaea, nanohaloarchaea and
may be similarly adapted to both environments. We reconstructed 4 draft genomes related to Bacteroidetes, Balneolaeota and Halobacteria and appraised their metabolism, osmoadaptation strategies and ecology. This study greatly improves the current understanding of saline soils microbiota.
Abstract
Andean wetlands hold extremophilic communities adapted to live in harsh conditions. Here, we investigated the microbial ecology of three high-altitude hypersaline ponds from La Puna region ...(Argentina) showing an increasing extent of desiccation by analyzing their lipid sedimentary record. We recreated the microbial community structure and the carbon metabolisms in each lacustrine system based on the molecular distribution of lipid biomarkers and their compound-specific carbon and hydrogen isotopic signatures. We detected lipid compounds considered to be biomarkers of cyanobacteria, sulfate-reducing bacteria, purple sulfur bacteria, and archaea in the three Andean ponds, as well as diatoms in the intermediate salinity system. The relative abundance of purple sulfur and sulfate-reducing bacteria decreased with salinity, whereas cyanobacteria and archaea decreased their relative abundance in the mid-saline pond to increase it again and became both prevailing at the highest salinity. Carbon fixation in the three ponds was driven by a combination of the reductive tricarboxylic acid cycle, the reductive pentose phosphate cycle, and the reductive acetyl-CoA pathway. This work is the first to describe molecular and isotopic lipid fingerprints in wetlands from the central Andean Puna, and serves as a basis for further biogeochemical studies in the area.
First report on lipids biomarkers and their compound specific isotopic composition (carbon and hydrogen) in high-altitude hypersaline ponds.
Halophilic
Archaea
are widely distributed globally in hypersaline environments. However, little is known of how dominant halophilic archaeal genera are distributed across environments and how they ...may co-associate across ecosystems. Here, the archaeal community composition and diversity from hypersaline environments (> 300 g/L salinity; total of 33 samples) in the Qaidam Basin of China were investigated using high-throughput Illumina sequencing of 16S rRNA genes. The archaeal communities (total of 3,419 OTUs) were dominated by the class
Halobacteria
(31.7–99.6% relative abundances) within the phylum
Euryarchaeota
(90.8–99.9%). Five predominant taxa, including
Halorubrum
,
Halobacterium
,
Halopenitus
,
Methanothrix
, and
Halomicrobium
, were observed across most samples. However, several distinct genera were associated with individual samples and were inconsistently distributed across samples, which contrast with previous studies of hypersaline archaeal communities. Additionally, co-occurrence network analysis indicated that five network clusters were present and potentially reflective of interspecies interactions among the environments, including three clusters (clusters II, III, and IV) comprising halophilic archaeal taxa within the
Halobacteriaceae
and
Haloferacaceae
families. In addition, two other clusters (clusters I and V) were identified that comprised methanogens. Finally, salinity comprising ionic concentrations (in the order of Na
+
> Ca
2+
> Mg
2+
) and pH were most correlated with taxonomic distributions across sample sites.
An extremely halophilic archaeon, strain F13-25
, was isolated from a marine saltern located in Isla Cristina, Huelva, on the south-west coast of Spain. The novel strain had pink-pigmented, ...non-motile, coccoid cells. Optimal growth was achieved at 25 % (w/v) NaCl, pH 7.5 and 37 °C. Strain F13-25
possessed two heterogeneous 16S rRNA genes (
and
) most closely related to
D108
(97.6-99.2 % sequence similarity) and
TNN28
(95.9-98.8 %). On the basis of the results of
gene sequence analysis, strain F13-25
was also closely related to
IBRC-M 10043
(89.9 %) and
TNN28
(92.3 %). Relatedness values, computed using the Genome-to-Genome Distance Calculator, between strain F13-25
and
IBRC-M 10043
and
IBRC-M 10760
were 34.6 and 36.2 %, respectively. Average nucleotide identity values based on orthoANI, ANIb and ANIm of strain F13-25
and
IBRC-M 10043
and
IBRC-M 10760
were 88.0 and 88.8, 87.1 and 87.6 %, and 89.2 and 89.6 %, respectively. All values were far below the threshold accepted for prokaryotic species delineation. The major polar lipids were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and one glycolipid chromatographically identical to sulfated diglycosyl diether. The DNA G+C content was 65.7 mol% (genome). The results of phylogenetic, phenotypic and chemotaxonomic analyses indicated that strain F13-25
represents a novel species of the genus
, for which the name
sp. nov., with type strain F13-25
(=CECT 9384
=IBRC-M 11176
), is proposed.
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