Saline-alkaline Lake Research Articles

In Situ Formation of Monohydrocalcite in Alkaline Saline Lakes of the Valley of Gobi Lakes: Prediction for Mg, Ca, and Total Dissolved Carbonate Concentrations in Enceladus’ Ocean and Alkaline-Carbonate Ocean Worlds

The nature of mineral precipitations in terrestrial alkaline soda lakes provides insights into the water chemistry of subsurface oceans on icy bodies in the outer solar system. Saturation analyses of terrestrial alkaline lakes have shown that the solution chemistries of lake waters are generally controlled by the presence of monohydrocalcite (MHC) and amorphous Mg-carbonate (AMC). However, direct observations of the formation of these metastable carbonates in natural alkaline lakes have been limited. This study provides evidence of in situ MHC formation in alkaline lakes, based on the water chemistry and mineralogy of suspended matter in Olgoy, Boon Tsagaan, and Orog Lakes (Valley of Gobi Lakes, Mongolia). The solution chemistries were close to saturation with respect to MHC and AMC, consistent with other alkaline lakes worldwide. Suspended matter was separated by the ultracentrifugation of lake water following freeze-drying. Our results show that MHC is the common mineral phase in the suspended matter. These observations confirm that MHC is the direct authigenic product of evaporation in alkaline lakes. The carbonate fraction in suspended matter from Olgoy Lake has a Mg/Ca ratio of 0.4, suggesting the formation of AMC in association with MHC. Based on the dissolution equilibria of AMC and MHC, we predict the Mg2+, Ca2+, and total dissolved carbonate concentrations in Enceladus’ ocean to be ~1 mmol/kg, ~10 μmol/kg, and 0.06–0.2 mol/kg, respectively, in the presence of AMC and MHC. We propose that the measurements of Mg contents in plumes will be key to constraining the total dissolved carbonate concentrations and chemical affinities of subsurface oceans on Enceladus and other alkaline-carbonate ocean worlds.

Ammonia excretion and blood gas variation in naked carp (Gymnocypris przewalskii) exposed to acute hypoxia and high alkalinity

Naked carp (Gymnocypris przewalskii), endemic to the saline-alkaline Lake Qinghai, have the capacity to tolerate combined hypoxia and high alkalinity. This study evaluated the effect of the interaction between carbonate alkalinity and hypoxia on ammonia excretion and blood gas variation in naked carp. Naked carp were subjected to normoxic, hypoxic and reoxygenation phases at two different carbonate alkalinity levels (CA0 = 0mmol/L; CA32 = 32mmol/L) for 4days. The ammonia excretion rate (JAmm) of the CA0 group rapidly decreased under hypoxia and recovered under normoxia for four consecutive days. The JAmm under CA32 also decreased under hypoxia and recovered to its previous level in the first 2days. However, the JAmm under CA32 was lower than that under CA0. The blood pO2, sO2 of CA0 and CA32 group was significantly reduced under hypoxia, after which both groups recovered. Blood pCO2 of the CA32 group was lower than CA0 throughout the experiment. There were no changes in haematocrit of the naked carp exposed to carbonate alkalinity and hypoxia. The alkaline water increased the pH of the blood and contributed to increased haemoglobin O2 affinity. Overall, the present findings reveal that naked carp is a tolerant species that can maintain main ionic homeostasis under severe alkalinity and hypoxia. The high alkaline water is beneficial for naked carp to adapt to hypoxic environment.

Description of Nitrincola elmenteitensis sp. nov.; a haloalkaliphilic bacterium isolated from Lake Elmenteita in Kenya

A bacterial strain designated E-48T was isolated from Lake Elmenteita, an alkaline saline lake within the East African rift valley. The cells were Gram-negative, motile, non-spore forming rods. Growth was observed at a pH range between 6.0 and 13.0 (optimum pH 9.5), salt concentration (w/v) up to 20% (optimum 5%) and the temperature for growth was between 14.0-44°C (optimum temperature 36°C). On the basis of 16S rRNA gene sequence similarity (99%), strain E-48T belonged to the genus Nitrincola (family Oceanospirillaceae, class Gammaproteobacteria). The DNA GC content was 46.4 mol%. The major cellular fatty acid was the mono-unsaturated 18:1 ω7c while the major isoprenoid quinone was Q-8. However, at the genome level, strain E-48T had a G+C difference of 7.17% from the genome of N. lacisaponensis DSM 16316T. Based on the various characteristics, it is proposed that the isolate represents a new species within the genus Nitrincola for which the name Nitrincola elmenteitensis is proposed. The type strain is E-48T (=DSM 26266T=LMG 28382T).

The novel strain Desmonostoc salinum CCM-UFV059 shows higher salt and desiccation resistance compared to the model strain Nostoc sp. PCC7120.

Desmonostoc salinum CCM-UFV059 (Desmonostoc) is a novel cyanobacterial strain of the order Nostocales isolated from a saline-alkaline lake. The acclimation towards salt and desiccation stress of Desmonostoc was compared to the related and well-characterized model strain Nostoc sp. PCC7120 (Nostoc). Salt-stressed cells of Desmonostoc maintained low cellular Na+ concentrations and accumulated high amounts of compatible solutes, mainly sucrose and to a lower extent trehalose. These features permitted Desmonostoc to grow and maintain photosynthesis at 2-fold higher salinities than Nostoc. Moreover, Desmonostoc also induced sucrose over-accumulation under desiccation, which allowed this strain to recover from this stress in contrast to Nostoc. Additional mechanisms such as the presence of highly unsaturated lipids in the membrane and an efficient ion transport system could also explain, at least partially, how Desmonostoc is able to acclimate to high salinities and to resist longer desiccation periods. Collectively, our results provide first insights into the physiological and metabolic adaptations explaining the remarkable high salt and desiccation tolerance, which qualify Desmonostoc as an attractive model for further analysis of stress acclimation among heterocystous N2 -fixing cyanobacteria.

Dissolved organic matter in a tropical saline-alkaline lake of the East African Rift Valley.

Saline-alkaline lakes of the East African Rift are known to have an extremely high primary production supporting a potent carbon cycle. To date, a full description of carbon pools in these lakes is still missing. More specifically, there is not detailed information on the quality of dissolved organic matter (DOM), the main carbon energy source for heterotrophs prokaryotes. We report the first exhaustive description of DOM molecular properties in the water column of a meromictic saline-alkaline lake of the East African Rift. DOM availability, fate and origin were studied either quantitatively, in terms of dissolved organic carbon (DOC) and nitrogen (DON) or qualitatively, in terms of optical properties (absorbance) and molecular characterization of solid-phase extracted DOM (SPE-DOM) through negative electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). DOM availability was high (DOC ∼ 8.1 mM in surface waters) and meromixis imprinted a severe quantitative and qualitative change on DOM pool. At the surface, DOM was rich in aliphatic and moderately in aromatic molecules and thus mirroring autochthonous microbial production together with photodegradation. At the bottom changes were extreme: DOC increased up to 5 times (up to 50 mM) and, molecular signature drifted to saturated, reduced and non-aromatic DOM suggesting intense microbial activity within organic sediments. At the chemocline, DOC was retained indicating that this interface is a highly reactive layer in terms of DOM processing. These findings underline that saline-alkaline lakes of the East African Rift are carbon processing hot spots and their investigation may broaden our understanding of carbon cycling in inland waters at large.

Occurrence, composition, and origin of analcime in sedimentary rocks of non-marine petroliferous basins in China

Abstract Natural analcime, a highly brittle aluminosilicate mineral that dissolves easily during diagenesis, occurs in the sedimentary rocks of eight main non-marine petroliferous basins in China. This mineral has been well documented for the past 30 years and has proved to be significant for the formation of high-quality hydrocarbon reservoirs. The present study fully reviews analcime occurrences, chemical compositions, Si/Al ratios, origin and controlling factors, and influence on the hydrocarbon reservoir quality in Permian to Paleogene sedimentary rocks. Previous research has shown that analcime is commonly distributed within argillaceous laminae (l-type); occurs as intergranular cement (c-type), replacement (r-type), and crack filling (f-type) forms; or is closely intergrown with other authigenic/exhalative minerals (a-type). Analcime in lacustrine basins is slightly Al-rich and Na-poor, and its Si/Al ratios range from 1.95 to 2.80. The geochemical compositions of the analcime- and ankerite-bearing exhalites are characterised by enrichment in light rare earth elements and 13C and depletion in heavy rare earth elements and 18O, with negative Eu and positive Ce anomalies. Diagenetic analcime forms by the alteration of volcanic glass, clays, or zeolite precursors in saline-alkaline lakes or during buried diagenetic stages in sedimentary rocks. In addition, it coexists with other authigenic zeolite, carbonate, and clay minerals as well as albite. Hydrothermal analcime presumably precipitates from hydrothermal fluids and is not dependent on a local precursor mineral or volcanic glass; this type is commonly related to exhalative mineralisation of hydrothermal springs. The formation of natural analcime is controlled by various factors such as the composition of the parent material, temperature prevalent during crystallisation, chemistry of the fluid phase, and thermodynamic characteristics of the geological environment. As zeolites are formed in alkaline fluid phases, they become unstable in acidic pore water. Secondary pores created by analcime mineral dissolution, and intercrystalline micropores among analcime minerals, are highly significant in hydrocarbon reservoirs. Analcime-bearing mudstone, siltstone, dolostone, and exhalite are favourable lithofacies for unconventional hydrocarbon accumulation owing to its high brittleness and selective dissolution of analcime and other associated minerals.

Phylogenetic and morphological diversity of culturable cyanobacteria from Lake Magadi in Kenya

Lake Magadi is an alkaline saline Lake in Kenya, which lies on the Great Eastern Rift valley. Although the lake is characterized by extremes of salt, pH and temperature, it supports diverse groups of cyanobacteria. In this study, we used different media to isolate novel groups of cyanobacteria. We recovered 11 isolates affiliated to the orders Chroococcales, Oscillatoriales, Pleurocapsales and Nostocales. Isolates affiliated to Chroococcidiopsis species had similarity values below 90% to currently characterized taxa indicating that these could be completely new phylotypes. This taxon has not been isolated before from the soda lake indicating the power of molecular techniques in identifying novel cyanobacterial taxa. Only two of the recovered isolates had 99% similarity to known organisms. Previous studies have mainly relied on microscopic examination and identification, which can lead to misidentification and subsequent assignment of an organism to the wrong taxon. The recovered isolates are a useful resource of more studies on taxonomy and secondary metabolite production.

Bacillus lacisalsi sp. nov., a moderately haloalkaliphilic bacterium isolated from a saline-alkaline lake.

An alkaliphilic and moderately halophilic strain, designated YSP-3T, characterised by optimal growth at pH 9.0 and at 8.0% (w/v) NaCl, was isolated from Yangshapao Lake, Jilin Province, China. Cells of this strain is Gram-positive, straight rods and form a central or sub-terminal ellipsoidal endospore. Phylogenetic analysis based on 16S rRNA gene sequences indicated that it was grouped in the genus Bacillus with Bacillus aurantiacus K1-5T and Bacillus populi FJAT-45347T as the close relative (97.5 and 97.2% 16S rRNA gene sequence similarity, respectively). Genomic relatedness between strain YSP-3T and its close relative was evaluated using average nucleotide identity, digital DNA-DNA hybridization and average amino acid identity with the values of 70.3-85.1%, 19.7-20.1% and 71.5-71.6%, respectively. Comparative genomics analysis showed that strain YSP-3T has distinct amino acid bias and significantly differences from foreign invasion events during evolution relative to the reference strains. Cell-wall peptidoglycan contains meso-diaminopimelic acid. The predominant polar lipids are phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol. The predominant quinone is menaquinone-7. The major fatty acids of strain YSP-3T are anteiso-C15:0, iso-C15:0, iso-C16:0, anteiso-C17:0 and Iso-C14:0. DNA G + C content of strain YSP-3T is 48.3mol%. Based on genomics analysis, physiological, biochemical and chemotaxonomic data, strain YSP-3T represent a novel species, for which the name Bacillus lacisalsi sp. nov. is proposed. The type strain is YSP-3T ( = ACCC 60365T = KCTC 33934T).

Depositional environments in an arid, closed basin and their implications for oil and gas exploration: The lower Permian Fengcheng Formation in the Junggar Basin, China

The Fengcheng Formation is a nonmarine, carbonate-dominated succession that formed under arid climatic conditions in a hydrologically closed basin. Two transects and two seismic profiles were examined, the characteristics and environmental significance of different lithofacies were studied, and a model of depositional environment divisions was proposed. The sedimentary model involved an alkaline lake in which the depositional environments consisted of a shallow saline lake margin, slope, saline lake center, and steep lake margin from northeast to southwest. The perennial central salty lake was located in the southwestern part of the study area, whereas there were widespread, low-gradient lake margins in the northeast, east, southeast, and southern parts of the study area. Lake-level fluctuations had a major influence on the shallow saline lake system and complicated the depositional environments in these areas. The deposits are derived from bedrock reworking, volcanic eruptions, and authigenic minerals that precipitated from brine during the hypersaline phase. Fine-grained terrigenous clastic sediments, volcanic ashes and dusts, and authigenic minerals mixed in the depocenter (concentration center of the brine pool), which was covered by high-salinity brines, and the depositional environment was anoxic as a result of salinity-based brine stratification. A thick sodium carbonate succession occurred in the depocenter of the ancient Mahu lake, where bedded sodium carbonate alternated with fine-grained, organic-rich tuff or tuffaceous hydrocarbon source rocks. Microorganisms bloomed in the alkaline, high-salinity brine, and the organic matter was well preserved, which is similar to those modern alkaline saline lakes in eastern Africa and western North America. Thus, the Permian Fengcheng Formation contains source rocks that formed in an alkaline saline lake.

Bioturbation in matgrounds at Lake Bogoria in the Kenya Rift Valley: implications for interpreting the heterogeneous early Cambrian seafloor

Modern burrowing organisms feed on microbial organic matter in matgrounds near hot springs on the margins of Lake Bogoria, a saline alkaline lake in the Kenya Rift Valley. The burrowers produce a low-diversity trace assemblage similar to those produced by undermat miners during the Ediacaran–Cambrian transition. Despite obvious differences in body plans and phylogenetic affinities, these modern animals feed on microbes in similar ways to those inferred for primitive bilaterians. With increasing distance from hot-spring vents, outflow channels and adjacent matgrounds, the diversity and depth of the traces increase and mixgrounds become dominant. This modern extreme environment gives clues for interpreting the heterogeneous early Cambrian seafloor, with: (1) the restriction of ‘pre-agronomic revolution’ matground substrates; and (2) expansion of adjacent ‘post-agronomic revolution’ mixground areas.

Barriers to genetic connectivity of smooth flatsedge (Cyperus laevigatus) among alkaline-saline lakes of Eastern Rift Valley (Kenya)

The saline-alkaline Rift Valley lakes of Kenya are isolated habitats supporting emergent halophytes on the shorelines. Cyperus laevigatus L. (Smooth flatsedge) is common to these endorheic lakes suggesting connectivity over long distances. The main objective of this study was to assess the amount and pattern of genetic diversity in C. laevigatus populations in wetlands and along shorelines of lakes of the Eastern Rift Valley in Kenya. The clonal, allelic and gene diversity, population genetic structure and fine-scaled spatial genetic structure were assessed on 204 C. laevigatus individuals from nine populations, using thirteen newly developed microsatellites. Cyperus laevigatus populations maintained high levels of clonal and allelic diversity, though with significant within-population inbreeding. No or only restricted local clonal growth over few metres could be found along shorelines of most lakes. A fine-scaled spatial genetic structure was revealed on sheltered populations indicating contemporary local dispersal from repeated seedling recruitment. Significant differentiation and isolation-by-distance was observed, supporting a stepping-stone model. A north to south gradient, as revealed from pairwise FST, PCoA, Structure and a Barrier analysis, included barriers between some lakes, with Lake Magadi fully separated. Bayesian clustering of individuals revealed a gene pool corresponding to the Great Nakuru-Elementaita basin. Historical hydrological connectivity during Holocene as well as geographical distances between Rift Valley lakes were proposed as major driving forces explaining the contemporary genetic structure.

Interaction between lakes’ surface water and groundwater in the Pantanal wetland, Brazil

The Nhecolândia subregion (area ~ 26,921 km2), in central-southern Pantanal, is marked by the presence of hundreds of alkaline–saline lakes, located on the top of sand hills, and thousands of non-alkaline lakes adjacent to the sand hills. This study aimed to provide a better understanding of the hydrological dynamics in the Nhecolândia, which is scarce and controversial, based on piezometric monitoring, isotopic data and chemical analyses of the surface water and groundwater of an alkaline–saline lake, a non-alkaline lake and the sand hill between them. The potentiometric data indicated that both alkaline–saline and non-alkaline lakes act as recharge zones, the former in all seasons and the later only in the wet season. These results are corroborated by downward flow near the zones of recharge, indicated by hydraulic head measurements in multilevel wells around the non-alkaline lake and in mini-piezometers installed in the studied alkaline–saline lake and two more lakes in the region. Also, δ18O and δ2H values of the alkaline–saline lake surface water became more depleted than the surrounding groundwater in the wet season, confirming that the inflow to the alkaline–saline lake in this season was by the more depleted rainwater and not by the isotopically enriched groundwater. The water chemistry data is also in agreement with recharge from the alkaline–saline lake, even though this recharge is limited by a low-K layer. Because of this layer, the non-alkaline lake does not dry off during the dry season. This set of evidence demonstrated that the groundwater recharge in the study area occurs in the topographical lows, through a process known as depression-focused recharge, which disagrees with previous studies of the area.

Salipaludibacillus keqinensis sp. nov., a moderately halophilic bacterium isolated from a saline-alkaline lake.

A novel Gram-stain positive, short rod, forming sub-terminal endospores of ellipsoidal shape, halophilic, alkaliphilic and aerobic bacterium, designated strain KQ-12T, was isolated from a saline-alkaline lake in China, and characterised by a polyphasic taxonomic approach. The isolate grew at 4-40°C (optimum, 25°C), at pH 8.0-10.0 (pH 9.0) and in the presence of 0-16% (w/v) NaCl (8%). 16S rRNA gene sequence similarity of KQ-12T to species in the genera Salipaludibacillus ranged from 96.6 to 98.1%. Phylogenetic trees indicated that the strain should be assigned to the genus Salipaludibacillus. The polar lipids of KQ-12T were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and an unidentified phospholipid and its major cellular fatty acids were anteiso-C15:0, anteiso-C17:0, iso-C15:0, and C16:0. The isoprenoid quinone was MK-7. These key chemotaxonomic properties also confirmed the affiliation of the strain to the genus Salipaludibacillus. However, some physiological, biochemical properties, low average nucleotide identity and low digital DNA-DNA hybridization relatedness values enabled the strain to be differentiated from closely related species of the genus Salipaludibacillus. Thus, KQ-12T can be classified as a novel species in the genus Salipaludibacillus, for which the name Salipaludibacillus keqinensis sp. nov. is proposed. The type strain is KQ-12T ( = ACCC 60430T = KCTC 33935T).

Very Low Phytoplankton Diversity in a Tropical Saline-Alkaline Lake, with Co-dominance of Arthrospira fusiformis (Cyanobacteria) and Picocystis salinarum (Chlorophyta)

Lake Dziani Dzaha (Mayotte Island, Indian Ocean) is a tropical thalassohaline lake which geochemical and biological conditions make it a unique aquatic ecosystem considered as a modern analogue of Precambrian environments. In the present study, we focused on the diversity of phytoplanktonic communities, which produce very high and stable biomass (mean2014–2015 = 652 ± 179 μg chlorophyll a L−1). As predicted by classical community ecology paradigms, and as observed in similar environments, a single species is expected to dominate the phytoplanktonic communities. To test this hypothesis, we sampled water column in the deepest part of the lake (18 m) during rainy and dry seasons for two consecutive years. Phytoplanktonic communities were characterized using a combination of metagenomic, microscopy-based and flow cytometry approaches, and we used statistical modeling to identify the environmental factors determining the abundance of dominant organisms. As hypothesized, the overall diversity of the phytoplanktonic communities was very low (15 OTUs), but we observed a co-dominance of two, and not only one, OTUs, viz., Arthrospira fusiformis (Cyanobacteria) and Picocystis salinarum (Chlorophyta). We observed a decrease in the abundance of these co-dominant taxa along the depth profile and identified the adverse environmental factors driving this decline. The functional traits measured on isolated strains of these two taxa (i.e., size, pigment composition, and concentration) are then compared and discussed to explain their capacity to cope with the extreme environmental conditions encountered in the aphotic, anoxic, and sulfidic layers of the water column of Lake Dziani Dzaha.

Application of the Carlson’s Trophic State Index for the Assessment of Trophic Status of Lake Simbi Ecosystem, a Deep Alkaline-Saline Lake in Kenya

Eutrophication is increasingly becoming the greatest threat to the ecological health of global water resources hence constant screening of the trophic state of these ecosystems is important. This study was aimed at defining the trophic status of Lake Simbi through the Carlson’s Trophic State Index (CTSI) which is based on the interactions of three water quality variables viz., Secchi depth (SD), total phosphorus (TP) and the chlorophyll-a (Chl-a). The classification scale for Trophic State Index (TSI) runs from 0 to 100, and the results of this study showed that the mean TSI for SD was 67.60, for TP was 118.56, for Chl-a was 74.86 and finally the overall CTSI was 87.01. These show that Lake Simbi is hypereutrophic which reflects the high concentration of nutrients in the lake. The lake suffers from cultural eutrophication which symptomatically manifests in the prevalent proliferation of algal bloom in the lake. The study therefore recommends adoption of an efficient multi-sectoral plan for monitoring and controlling nutrients loading and other pollutants input into the lake.

Natural and anthropogenic influences on the Nhecolândia wetlands, SE Pantanal, Brazil

Abstract The Nhecolândia region covers the southern wetlands of the Pantanal basin in Brazil. Characterized by myriad shallow freshwater and alkaline–saline lakes, the distinct natural features of the Nhecolândia wetland make it highly sensitive to climate change and the effects of human activities. This paper summarizes the natural and social aspects that have affected this delicate wetland and potential future impacts. We analysed the response of the wetland to historical changes in climate and human activity and used this understanding to forecast the response of the wetland to future changes. The data presented here show that this region is particularly sensitive to alterations in the flood regime, droughts and deforestation, which are intrinsically related to both global and local changes in climate and the intensification of cattle-ranching activities, which include deforestation and the introduction of cultivated pastures.

The hydrocarbon generation potential and migration in an alkaline evaporite basin: The Early Permian Fengcheng Formation in the Junggar Basin, northwestern China

Abstract The Permian Fengcheng Formation in the Mahu Sag in the Junggar Basin represents deposition in a rare alkaline saline lake, with hydrologically closed conditions, alkaline saline brines, and intense volcanic activity. The Fengcheng Formation contains large volumes of high-quality source rocks, which form not only in the depocenter but also in the wide, shallow lake margins. The source rocks analyzed in this study are different from those in most other ancient lakes in the following aspects: genesis and occurrence of organic matter, kerogen type, lithological composition, and hydrocarbon migration pathway. This study showed that the Fengcheng Formation has high hydrocarbon generation potential and that combinations of multiple paths enhanced the hydrocarbon expulsion and migration. Benthic microbial mats and algae that bloomed in the alkaline saline lake represent the dominant types of organic matter. Due to their specific composition, the evaporites may have catalyzed hydrocarbon generation via organic-inorganic interactions, while intergranular seams in bedded/laminated evaporites provided paths for hydrocarbon migration. Stylolites, with high contents of brittle minerals and low clay content, also allowed favorable paths for hydrocarbon expulsion and migration. Combining hydrocarbon expulsion fractures in the organic-rich laminae, fractures and microfractures caused by compressive tectonic stress, pathway networks formed that enhanced the efficiencies of both hydrocarbon expulsion and migration.

Extending the ecological distribution of Desmonostoc genus: proposal of Desmonostoc salinum sp. nov., a novel Cyanobacteria from a saline-alkaline lake.

Cyanobacteria is an ancient phylum of oxygenic photosynthetic microorganisms found in almost all environments of Earth. In recent years, the taxonomic placement of some cyanobacterial strains, including those belonging to the genus Nostocsensu lato, have been reevaluated by means of a polyphasic approach. Thus, 16S rRNA gene phylogeny and 16S-23S internal transcribed spacer (ITS) secondary structures coupled with morphological, ecological and physiological data are considered powerful tools for a better taxonomic and systematics resolution, leading to the description of novel genera and species. Additionally, underexplored and harsh environments, such as saline-alkaline lakes, have received special attention given they can be a source of novel cyanobacterial taxa. Here, a filamentous heterocytous strain, Nostocaceae CCM-UFV059, isolated from Laguna Amarga, Chile, was characterized applying the polyphasic approach; its fatty acid profile and physiological responses to salt (NaCl) were also determined. Morphologically, this strain was related to morphotypes of the Nostocsensu lato group, being phylogenetically placed into the typical cluster of the genus Desmonostoc. CCM-UFV059 showed identity of the 16S rRNA gene as well as 16S-23S secondary structures that did not match those from known described species of the genus Desmonostoc, as well as distinct ecological and physiological traits. Taken together, these data allowed the description of the first strain of a member of the genus Desmonostoc from a saline-alkaline lake, named Desmonostoc salinum sp. nov., under the provisions of the International Code of Nomenclature for algae, fungi and plants. This finding extends the ecological coverage of the genus Desmonostoc, contributing to a better understanding of cyanobacterial diversity and systematics.

Biochemical and functional characterization of a novel thermoacidophilic, heat and halo-ionic liquids tolerant endo-β-1,4-glucanase from saline-alkaline lake soil microbial metagenomic DNA

The lignocellulosic biomass usually need pre-treatment with acid at high temperature or solved in ionic liquid (IL) before cellulases hydrolysis. Thus, thermoacidophilic, thermostable and IL-tolerant cellulases are greatly desired, but rarely reported. In this study, a novel endo-β-1,4-glucanase gene nmGH45 was directly cloned from saline-alkaline lake soil microbial metagenomic DNA and expressed in Pichia pastoris. Recombinant NMgh45 was active and stable at pH 3.0–9.0, with maximum activity at pH 4.5 and >80% residual activities at pH 3.0–11.0. It exhibited maximal activity at 60–70 °C and remaining >90% and 68% residual activities at 80 °C for 2 h and 90 °C for 1 h. Besides, NMgh45 retained >88% relative activities in 4 M NaCl, and was stable for 24 h. Significantly, it was highly IL-tolerant, remaining 92.8% and 43.8% residual activities in 10% and 20% 1-butyl-3-methylimidazolium chloride. Compared with other non-halo-tolerant counterparts, NMgh45 was enriched with acidic amino acids on the protein surface, and the conformation of NMgh45 was stable at high salinity condition based on molecular dynamic simulation. Finally, the productivity of recombinant NMgh45 was optimized at multi-levels. The thermoacidphilic and acid-alkaline-halo-tolerant properties make NMgh45 a promising enzyme for basic research and industrial applications.

Draft Genome Sequence of Bacillus urumqiensis BZ-SZ-XJ18T, a Moderately Haloalkaliphilic Bacterium Isolated from a Saline-Alkaline Lake.

ABSTRACTThe moderately haloalkaliphilic bacterium Bacillus urumqiensis BZ-SZ-XJ18T was isolated from a saline-alkaline lake located in the Xinjiang Uyghur Autonomous Region of China. Optimum growth occurred at the total Na+ concentration of 1.08 M, with a broad optimum pH of 8.5 to 9.5. The draft genome consists of approximately 3.28 Mb and contains 3,228 predicted genes. A number of genes associated with adaptation strategies for osmotic balance and alkaline pH homeostasis were identified, providing pertinent insight into specific adaptations to the double-extreme environment.