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A Gram-stain-positive, aerobic, endospore-forming and rod-shaped bacterium (KQ-3 T ), which grew at 10-45 °C (optimum 35 °C), pH 8.0-10.5 (optimum pH 9.0) and in the presence of 0-16 % (w/v) NaCl (optimum 3.0 %), was isolated from a soda lake and identified as representing a novel species using a polyphasic taxonomic approach. Strain KQ-3 T was catalase-positive, oxidase-negative and non-motile. Phylogenetic analysis based on 16S rRNA gene sequence affiliated KQ-3 T to the genus Alteribacter and showed the highest similarities to Alteribacter natronophilus M30 T (97.90 %), Alteribacter aurantiacus K1-5 T (97.84 %) and Alteribacter populi FJAT-45347 T (97.22 %). Digital DNA-DNA hybridization and average nucleotide identity analyses revealed that KQ-3 T displayed 21.4 and 72.81% genomic DNA relatedness with the most closely related strain, A. natronophilus M30 T , respectively. KQ-3 T contained all of the conserved signature indels that are specific for members of the genus Alteribacter . The DNA G+C content was 45.03 mol%. The cell-wall peptidoglycan contained meso -diaminopimelic acid and the polar lipids consisted of phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol and one unidentified phospholipid. The predominant menaquinone was MK-7 (100%) and the major fatty acids (>10 %) comprised anteiso-C 15 : 0 , iso-C 15 : 0 and iso-C 16 : 0 . Based on the data from the current polyphasic studies, KQ-3 T represents a novel species of the genus Alteribacter , for which the name Alteribacter keqinensis sp. nov. is proposed. The type strain is KQ-3 T (=ACCC 61799 T =KCTC 33933 T ).

A haloalkaliphilic strain (IM 1326 T ) was isolated from brine sampled at a soda lake in the Inner Mongolia Autonomous Region, China. Cells of the strain were rod-shaped and motile. Strain IM 1326 T was able to grow at 4-42 °C (optimum, 37 °C) with 0-13.0 % (w/v) NaCl concentrations (optimum at 4.0-6.0 %) and at pH 7.5-11.0 (optimum at 9.0-10.0). The 16S rRNA gene phylogenetic analysis revealed that the isolate belongs to the genus Aliidiomarina and is closely related to the type strains of Aliidiomarina sanyensis (95.8 % sequence similarity), Aliidiomarina shirensis (95.7 %), Aliidiomarina iranensis (95.4 %) and Aliidiomarina haloalkalitolerans (95.3 %). The whole genome of strain IM 1326 T was sequenced, and the genomic DNA G+C content was 49.7 mol%. Average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization values between the isolate and the related Aliidiomarina species were 68.1-84.9 %, 76-78 % and 18.4-20.4 %, respectively. The respiratory quinone was ubiquinone-8. The polar lipid profile included diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and one unidentified aminophospholipid. The predominant cellular fatty acids were summed feature 9 (10-methyl-C 16 : 0 /iso-C 17 : 1   ω 9 c , 22.2 %), iso-C 15 : 0 (16.1 %) and iso-C 17 : 0 (13.1 %). Based on the results of phylogenetic analysis, genome relatedness, and the physiological and chemotaxonomic properties of the isolate, strain IM 1326 T is considered to represent a novel species of the genus Aliidiomarina , for which the name Aliidiomarina halalkaliphila sp. nov. is proposed (type strain IM 1326 T =CGMCC 1.17056 T =JCM 34227 T ).

A Gram-stain-negative, oxidase- and catalase-positive, rod-shaped, creamy white coloured bacterial strain, DMG-N-6 T , was isolated from a water sample of Lake Fertő/Neusiedler See (Hungary). Phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain forms a distinct linage within the family Rhodobacteraceae . Its closest relatives are Tabrizicola alkalilacus DJC T (96.76% similarity) and Tabrizicola piscis K13M18 T (96.76%), followed by Tabrizicola sediminis DRYC-M-16 T (96.69 %), Rhodobacter sediminicola JA983 T (96.62 %), Tabrizicola aquatica RCRI19 T (96.47 %) and Cereibacter johrii JA192 T (96.18 %). The novel bacterial strain favours an alkaline environment (pH 8.0-12.0) and grows optimally at 18-28°C in the presence of 2-4 % (w/v) NaCl. Cells of DMG-N-6 T were motile by a single subpolar flagellum. Bacteriochlorophyll a was not detected. The predominant respiratory quinone was ubiquinone Q-10. The major cellular fatty acid was C 18:1 ω 7 c . The polar lipid profile comprised phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylserine, phosphatidylcholine, an unidentified phospholipid and five unidentified lipids. The assembled draft genome of strain DMG-N-6 T had 52 contigs with a total length of 4 219 778 bp and a G+C content of 64.3 mol%. Overall genome-related indices (ANI <77.8 %, AAI <69.0 %, dDDH <19.6 %) with respect to close relatives were all significantly below the corresponding threshold to demarcate bacterial genus and species. Strain DMG-N-6 T (=DSM 108208 T =NCAIM B.02645 T ) is strongly different from its closest relatives and is suggested as the type strain of a novel species of a new genus in the family Rhodobacteraceae , for which the name Szabonella alba gen. nov., sp. nov. is proposed.

Two novel alkaliphilic aerobic organotrophic bacteria have been isolated from a moderately saline and alkaline East African soda lake. The new isolates grow at pH values between 6 and 10, with a pH optimum for growth of 9.0, and at a salt concentration between 0% and 10% (w/v). Phylogenetic analysis based on 16S rDNA sequence shows that these isolates are very closely related (99.6% similarity) and are members of the monospecific genus Dietzia (98.8% and 98.7% similarity). DNA/DNA hybridization revealed a relatedness of 83% between the two isolates, but only 8% between them and the type strain Dietzia maris. The G + C content as measured by thermal denaturation is 66.1 mol%. Phenotypic comparisons between D. maris and one isolate showed that they share very similar morphological and chemotaxonomic properties, but differ significantly in carbon source utilization profiles and halotolerance in alkaline medium. We propose a second species of this genus which we name Dietzia natronolimnaios (type strain 15LN1 = CBS 107.95). [ABSTRACT FROM AUTHOR]

The article discusses the study regarding the chemical composition of the meromictic soda Lake Doroninskoe located in the eastern Transbaikalia, Russia. Topics include the stability anaerobic conditions provided by the density stratification of the water column, the role of microbial communities in process of producing and destructing the lakes, and the clear expression of the isotopic composition of carbon and oxygen carbonates.

Alkaline lakes are considered some of the most extreme aquatic environments on Earth and are thus of significance to our understanding of the biogeochemistry of extreme environments. However, the environmental evolution of these lakes (especially in ancient times) temporally and spatially is still poorly understood due to the unavailability of suitable samples. Here we present a case study of the Late Paleozoic Fengcheng Formation in the Junggar Basin, NW China, based on organic (biomarker) as well as inorganic (elemental) geochemical approaches. Results show that the Fengcheng Formation was deposited in a non-marine environment, as illustrated by the absence of 24- n -propylcholestanes and 24-isopropylcholestanes combined with the established fossil and sodium-carbonate evaporite records (wegscheiderite and trona). In detail, based on the biomarker assemblages in general, the Fengcheng Formation formed in an anoxic, hypersaline, stratified lacustrine environment. Temporally, the lower part of the formation (the lower two members F 1 and F 2) was formed under stable anoxic and stratified conditions with higher salinity, while the upper part (the third member F 3) had higher freshwater influx, which reduced the salinity and resulted in relatively higher terrestrial organic matter input. Spatially, the central region of the alkaline lake was influenced by hydrothermal springs, while the marginal region was more affected by volcanic activities resulting in clay-rich and suboxic environments during F 3. Our work suggests that the spatiotemporal evolution of alkaline lakes is multi-stage and heterogeneous, with hydrothermal and volcanic influence under restricted conditions and a dry climate. • Paleoenvironmental evolution of a late Paleozoic alkaline lake is detailed mainly based on biomarkers. • Absence of 24-n-propylcholestanes and 24-isopropylcholestanes indicate a lacustrine environment. • The lake environment is generally anoxic, hypersaline, and water-stratified. • The lake evolution is multi-stage and stepwise under restricted environments and dry climate. • The lake evolution possibly has hydrothermal and volcanic influence. [ABSTRACT FROM AUTHOR]

Alkaline (pH > 8.5) lakes have been common features of Earth's surface environments throughout its history and are currently among the most biologically productive environments on the planet. The chemistry of alkaline lakes favors the deposition of aluminum-poor magnesian clays (e.g., sepiolite, stevensite, and kerolite) whose chemistry and mineralogy may provide a useful record of the biogeochemistry of the lake waters from which they were precipitated. In this forward-looking review, we present six data-driven, testable hypotheses devoted to furthering our understanding of the biogeochemical conditions in paleolake waters based on the geochemical behavior of Mg and SiO2. In the development of these hypotheses, we bring together a compilation of modern lake water chemistry, recently published and new experimental data, and empirical, thermodynamic, and kinetic relationships developed from these data. We subdivide the hypotheses and supporting evidence into three categories: (1) interpreting paleolake chemistry from mineralogy; (2) interpreting the impact of diatoms on alkaline lake sedimentation; and (3) interpreting depositional mineralogy based on water chemistry. We demonstrate the need for further investigation by discussing evidence both for and against each hypothesis, which, in turn, highlights the gaps in our knowledge and the importance of furthering our understanding of the relevant geological and biological systems. The focused testing of these hypotheses against modern occurrences and the geologic record of alkaline lakes can have profound implications for the interpretation of the paleo-biogeochemistry and paleohabitability of these systems on Earth and beyond. [ABSTRACT FROM AUTHOR]

Mineral vesicles and chemical gardens are self-organized biomimetic structures that form via abiotic mineral precipitation. These membranous structures are known to catalyze prebiotic reactions but the extreme conditions required for their synthesis has cast doubts on their formation in nature. Apart from model solutions, these structures have been shown to form in serpentinization-driven natural silica-rich water and by fluid-rock interaction of model alkaline solutions with granites. Here, for the first time, we demonstrate that self-assembled hollow mineral vesicles and gardens can be synthesized in natural carbonate-rich soda lake water. We have synthesized these structures by a) pouring saturated metal salt solutions, and b) by immersing metal salt pellets in brines collected from Lake Magadi (Kenya). The resulting structures are analyzed by using SEM coupled with EDX analysis, Raman spectroscopy, and powder X-ray diffraction. Our results suggest that mineral self-assembly could have been a common phenomenon in soda oceans of early Earth and Earth-like planets and moons. The composition of the obtained vesicles and gardens confirms the recent observation that carbonate minerals in soda lakes sequestrate Ca, thus leaving phosphate behind in solution available for biochemical reactions. Our results strengthens the proposal that alkaline brines could be ideal sites for "one-pot" synthesis of prebiotic organic compounds and the origin of life. [ABSTRACT FROM AUTHOR]

Despite significant interest and past work to elucidate the phylogeny and photochemistry of species of the Heliobacteriaceae, genomic analyses of heliobacteria to date have been limited to just one published genome, that of the thermophilic species Heliobacterium (Hbt.) modesticaldum str. Ice1T. Here we present an analysis of the complete genome of a second heliobacterium, Heliorestis (Hrs.) convoluta str. HHT, an alkaliphilic, mesophilic, and morphologically distinct heliobacterium isolated from an Egyptian soda lake. The genome of Hrs. convoluta is a single circular chromosome of 3.22 Mb with a GC content of 43.1% and 3263 protein-encoding genes. In addition to culture-based observations and insights gleaned from the Hbt. modesticaldum genome, an analysis of enzyme-encoding genes from key metabolic pathways supports an obligately photoheterotrophic lifestyle for Hrs. convoluta. A complete set of genes encoding enzymes for propionate and butyrate catabolism and the absence of a gene encoding lactate dehydrogenase distinguishes the carbon metabolism of Hrs. convoluta from its close relatives. Comparative analyses of key proteins in Hrs. convoluta, including cytochrome c553 and the Fo alpha subunit of ATP synthase, with those of related species reveal variations in specific amino acid residues that likely contribute to the success of Hrs. convoluta in its highly alkaline environment. [ABSTRACT FROM AUTHOR]

The genus Thioalkalivibrio comprises sulfur-oxidizing bacteria thriving in soda lakes at high pH and salinity. Depending on the geographical location and the season, these lakes can strongly vary in temperature. To obtain a comprehensive understanding of the molecular and physiological adaptations to low temperature, we compared the responses of two Thioalkalivibrio strains to low (10°C) and high (30°C) temperatures. For this, the strains were grown under controlled conditions in chemostats and analyzed for their gene expression (RNA sequencing [RNA-Seq]), membrane lipid composition, and glycine betaine content. The strain Thioalkalivibrio versutus AL2 T originated from a soda lake in southeast Siberia that is exposed to strong seasonal temperature differences, including freezing winters, whereas Thioalkalivibrio nitratis ALJ2 was isolated from an East African Rift Valley soda lake with a constant warm temperature the year round. The strain AL2 T grew faster than ALJ2 at 10°C, likely due to its 3-fold-higher concentration of the osmolyte glycine betaine. Moreover, significant changes in the membrane lipid composition were observed for both strains, leading to an increase in their unsaturated fatty acid content via the Fab pathway to avoid membrane stiffness. Genes for the transcriptional and translational machinery, as well as for counteracting cold-induced hampering of nucleotides and proteins, were upregulated. Oxidative stress was reduced by induction of vitamin B 12 biosynthesis genes, and growth at 10°C provoked downregulation of genes involved in the second half of the sulfur oxidation pathway. Genes for intracellular signal transduction were differentially expressed, and interestingly, AL2 T upregulated flagellin expression, whereas ALJ2 downregulated it. IMPORTANCE In addition to their haloalkaline conditions, soda lakes can also harbor a variety of other extreme parameters, to which their microbial communities need to adapt. However, for most of these supplementary stressors, it is not well known yet how haloalkaliphiles adapt and resist. Here, we studied the strategy for adaptation to low temperature in the haloalkaliphilic genus Thioalkalivibrio by using two strains isolated from soda lakes with different temperature regimes. Even though the strains showed a strong difference in growth rate at 10°C, they exhibited similar molecular and physiological adaptation responses. We hypothesize that they take advantage of resistance mechanisms against other stressors commonly found in soda lakes, which are therefore maintained in the bacteria living in the absence of low-temperature pressure. A major difference, however, was detected for their glycine betaine content at 10°C, highlighting the power of this osmolyte to also act as a key compound in cryoprotection., (Copyright © 2021 Ahn et al.)

The saline-alkaline lakes (soda lakes) are the habitat of the haloalkaliphilic cyanobacterium Anabaenopsis elenkinii , the type species of this genus. To obtain robust phylogeny of this type species, we have generated whole-genome sequencing of the bloom-forming Anabaenopsis elenkinii strain CCIBt3563 isolated from a Brazilian soda lake. This strain presents the typical morphology of A. elenkinii with short and curved trichomes with apical heterocytes established after separation of paired intercalary heterocytes and also regarding to cell dimensions. Its genome size is 4 495 068 bp, with a G+C content of 41.98 %, a total of 3932 potential protein coding genes and four 16S rRNA genes. Phylogenomic tree inferred by RAxML based on the alignment of 120 conserved proteins using GTDB-Tk grouped A. elenkinii CCIBt3563 together with other genera of the family Aphanizomenonaceae. However, the only previous available genome of Anabaenopsis circularis NIES-21 was distantly positioned within a clade of Desikacharya strains, a genus from the family Nostocaceae. Furthermore, average nucleotide identity values from 86-98 % were obtained among NIES-21 and Desikacharya genomes, while this value was 76.04 % between NIES-21 and the CCIBt3563 genome. These findings were also corroborated by the phylogenetic tree of 16S rRNA gene sequences, which also showed a strongly supported subcluster of A. elenkinii strains from Brazilian, Mexican and Kenyan soda lakes. This study presents the phylogenomics and genome-scale analyses of an Anabaenopsis elenkinii strain, improving molecular basis for demarcation of this species and framework for the classification of cyanobacteria based on the polyphasic approach.

Lake Van fish ( Alburnus tarichi Guldenstadt 1814) is the only fish that can adapt to the extreme conditions (pH 9.8 salinity 0.2% and alkalinity 151.2 meq/L) of Lake Van. In this study, it was aimed to determine the cytotoxic and genotoxic effects of chlorpyrifos (CPF) on Lake Van fish primary gill cell culture. Gill epithelium from Lake Van fish was isolated enzymatically and grown in primary culture on Leibovitz's L-15 medium. After different doses (0.01, 0.1, 1, and 10 μM) of CPF were applied to the gill cells, the total oxidant status (TOS), total antioxidant status (TAS), malondialdehyde (MDA), and DNA damage levels (8-hydroxyguanine (8-OHdG)) were examined at the end of 24 and 48 h. It was determined that the TOS, MDA, and 8-OHdG levels increased in the cells exposed to high doses (1 and 10 μM) of CPF and the TAS was decreased ( P  < 0.05). It was revealed from this study that CPF administered at a dose higher than 1 μM can cause oxidative stress and DNA damage in the primary gill cell culture of Lake Van fish. In addition, the findings showed that Lake Van fish primary gill cell culture was useful in determining the effects of toxic substances likely to be the contaminants of a lake., (© The Author(s) 2020. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The bacterial isolates of genus Rhodococcus are best known for their significant biodegradation abilities. Here, we report the data related to draft genome sequencing of Rhodococcus rhodochrous strain SPC17 isolated from sediments of Lonar Lake. The de novo assembly of 1598096 Illumina's paired-end sequencing reads resulted in 51 contigs for an overall genome assembly size of 4.98Mb. A total of 4546 genes were predicted using the National Center for Biotechnology Information- Prokaryotic Genome Annotation Pipeline (NCBI-PGAP). RAST server-based annotation of the Rhodococcus strain SPC17 genome resulted in a total of 295 subsystems with 25% subsystem coverage. The data on the draft genome shotgun project are accessible at NCBI-GenBank under the accession number WUUR00000000. Our data resource will facilitate further molecular and genomic studies of diverse hydrocarbon catabolizing genes present in Rhodococcus rhodochrous strain SPC17., (© 2020 The Authors.)

An alkaliphilic, moderately halophilic, heterotrophic, rod-shaped, spore-forming bacterium (M30 T ) was isolated from a sediment sample collected from a soda lake (Lake Magadi, Tanzania). Strain M30 T was strictly aerobic, catalase-positive, oxidase-negative and non-motile. Growth occurred at 12-43 °C (optimum, 25-30 °C), at pH 8.0-12 (optimum, pH 9.5-10) and at salinities of 0.5-15 % (w/v) NaCl (optimum 5 %). It utilized various sugars and organic acids as sole carbon sources and was positive for amylase, cellulase, gelatinase, protease and xylanase activities. The cell-wall peptidoglycan contained meso -diaminopimelic acid and the polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, one unidentified lipid and one unidentified phospholipid. The DNA G+C content was 48.9 mol%. The predominant menaquinone was MK-7 and the major fatty acids (>10 %) comprised anteiso-C 15 : 0 , iso-C 15 : 0 , and anteiso-C 17 : 0 . Phylogenetic analysis based on 16S rRNA gene sequence affiliated M30 T to the genus Bacillus and showed the highest similarities to Bacillus populi FJAT-45347 T (96.4 %) and Bacillus aurantiacus K1-5 T (96.2 %). Based on the data from the current polyphasic study, M30 T represents a novel species of the genus Bacillus , for which the name Bacillus natronophilus sp. nov. is proposed. The type strain is M30 T (=JCM 32118 T =CGMCC 1.16739 T =MCC 3010 T ).

Lake Van, the largest soda lake in the world, is a key area where climatic changes are recorded by well-preserved sedimentary successions. In spite of the existence of such sequences, the ancient lake levels are still under debate. Here, we present U/Th ages of tufa layers exposed along the northern margin of the lake near the town of Adilcevaz. Tufa are interpreted to form during humid and temperate climate conditions in the contact zone between the highly alkaline lake water – rich in bicarbonate and carbonate ions – and calcium-rich groundwater. These contact zones most likely appear near shore. Thus, U/Th ages and altitude of the tufa present minimum ancient lakestands. The tufas obtained in our study are dated between 112.7 and 19.3 ka. They are interpreted to record two transgressional intervals, the first starting at 1701 meters above sea level (masl) altitude at 112.7 ka reaching 1706 masl at 72.5 ka (based on three U/Th ages). The second transgression starts at the present Lake Van level of 1646 masl at 30.1 ka, reaching 1725 masl at 19.3 ka (based on 15 U/Th ages). Comparison with climate proxies reveals that the first transgression was caused by intensified precipitation accompanied by warming, while the second transgression was triggered mainly by warming that initiated melting of glaciers. The lake-level fluctuations described here are almost in line with the ones gathered from dated lake terraces but contradict lake-level reconstruction based on pore water salinity. • U/Th ages of tufa layers found at Lake Van record minimum paleo-lakestands. • Lake Van level was about 80 m higher than today at around 20 ka. • Detailed mapping of tufa stratigraphy allows conclusion on lake-level fluctuations. [ABSTRACT FROM AUTHOR]