Halophilic Research Articles

Ecological success of extreme halophiles subjected to recurrent osmotic disturbances is primarily driven by congeneric species replacement.

To understand how extreme halophiles respond to recurrent disturbances, we challenged the communities thriving in salt-saturated (~36% salts) ~230L brine mesocosms to repeated dilutions down to 13% (D13 mesocosm) or 20% (D20 mesocosm) salts each time mesocosms reached salt saturation due to evaporation (for 10 and 17cycles, respectively) over 813days. Depending on the magnitude of dilution, the most prevalent species, Haloquadratum walsbyi and Salinibacter ruber, either increased in dominance by replacing less competitive populations (for D20, moderate stress conditions), or severely decreased in abundance and were eventually replaced by other congeneric species better adapted to the higher osmotic stress (for D13, strong stress conditions). Congeneric species replacement was commonly observed within additional abundant genera in response to changes in environmental or biological conditions (e.g. phage predation) within the same system and under a controlled perturbation of a relevant environmental parameter. Therefore, a genus is an ecologically important level of diversity organization, not just a taxonomic rank, that persists in the environment based on congeneric species replacement due to relatively high functional overlap (gene sharing), with important consequences for the success of the lineage, and similar to the success of a species via strain-replacement. Further, our results showed that successful species were typically accompanied by the emergence of their own viral cohorts, whose intra-cohort diversity appeared to strongly covary with, and likely drive, the intra-host diversity. Collectively, our results show that brine communities are ecologically resilient and continuously adapting to changing environments by transitioning to alternative stable states.

Halorubrum miltondacostae sp. nov., a potential polyhydroxyalkanoate producer isolated from an inland solar saltern in Rio Maior, Portugal

One hundred and sixty-three extreme halophiles were recovered from a single sample collected from an inland solar saltern in Rio Maior. Based on random amplified polymorphic DNA (RAPD) profiles and partial 16S rRNA gene sequencing 125 isolates were identified as members of the Archaea domain within the genus Halorubrum. Two strains, RMP-11T and RMP-47, showed 99.1 % sequence similarity with the species Halorubrum californiense based on phylogenetic analysis of the 16S rRNA gene sequence. However, phylogenetic analysis based on five housekeeping genes, atpB, EF-2, glnA, ppsA and rpoB’, showed Halorubrum coriense as the closest related species with 96.7 % similarity. The average nucleotide identity (ANI) of strains RMP-11T, RMP-47 and species Hrr. coriense were within the range of 90.0–90.5 %, supporting that strains RMP-11T and RMP-47 represent a novel species of the genus Halorubrum. These strains formed red-pigmented colonies that were able to grow in a temperature range of 25–50 °C. Polyhydroxyalkanoate (PHA) granules were detected in both strains. The polar lipid profile was identical to the neutrophilic species of the genus Halorubrum. The Rio Maior sample from which both strains were isolated was metagenome sequenced. We identified five metagenome-assembled genomes representing novel Halorubrum species but distinct from the species represented by strains RMP-11T and RMP-47. Based on phylogenetic, phylogenomic, comparative genomics, physiological and chemotaxonomic parameters, we describe a new species of the genus Halorubrum represented by strains RMP-11T (=CECT 30760T = DSM 115521T) and RMP-47 (=CECT 30761 = DSM 115541) for which we propose the name Halorubrum miltondacostae sp. nov.

Isolation and Identification of Halophilic Bacteria Isolated from Mangrove Soil in Blue Lagoon, Port Dickson, Negeri Sembilan

Halophiles bacteria are capable of tolerating and surviving in extreme salinity due to the special biological structure that it possesses. Classification of halophilic bacteria includes slight, moderate, and extreme halophiles which range from low to high concentrations of salt. Biotechnological products yielded from bacteria residing in saline environment are proven to be valuable in a few industries. The isolated halophilic bacteria may yield powerful biomolecules such as enzymes which can enhance plant development, hence boosting agricultural industries. However, the insufficient data related to halophiles available in Malaysia may reduce the potential use of these bacteria in related industries. The goal of this study is to isolate and identify the potential halophilic bacteria and to determine the tolerance of halophiles in different concentrations of salt. Collection of soil samples was done at the mangrove soil in Blue Lagoon, Port Dickson, Negeri Sembilan. Isolation and purification of halophiles was done on nutrient agar media supplemented with 3% salt. Next, Gram-staining was performed on 4 colonies of bacteria with different types of single colony appearances. Then, the selected bacteria with different colony and morphological characteristics were tested in nutrient broth supplemented with 0%, 3%, 10% and 20% of salt. Molecular identification was conducted which involved DNA extraction and Polymerase Chain Reaction. All 4 isolates selected were tested to be Gram-stain positive and possessed rod-shaped. The bacteria have various salinity tolerance levels which may be due to the presence of different enzymes produced in their cells. Gene sequences and phylogenetic tree were analyzed based on 16s rRNA sequences to identify the species of the isolates. At the end of the experiment, isolate 2A1 and 2A4 were identified as Bacillus sp., while isolate 2A2 and 2A3 were identified as Cytobacillus oceanisediminis.

Determination of Minimum Inhibitory Concentrations of Sophorolipids Against Selected Halotolerant and Moderately Halophilic Bacteria, and Extremely Halophilic Archaea Isolated from Salt Samples and Salted Skins

Determination of Minimum Inhibitory Concentrations of Sophorolipids Against Selected Halotolerant and Moderately Halophilic Bacteria, and Extremely Halophilic Archaea Isolated from Salt Samples and Salted Skins

Enchelyothrix muria n. gen, n. sp., (Ciliophora, Litostomatea, Spathidiida), an extreme halotroph spathidiid from Maharloo Lake, Iran

Although free-living ciliated protists (Ciliophora) commonly inhabit aquatic and terrestrial biotopes of mild to moderate salinity (PSS-practical salinity scale S = 10–150), very few have adapted to life at more extreme salinities (>150 to saturation). Such extreme halophiles or halotrophs are of interest from the standpoints of evolution, cell physiology, ecology, and even astrobiology. In this work, we present the morphology, 18S rRNA gene sequence, and phylogenetic analysis of a novel spathidiid ciliate (Ciliophora, Litosatomatea) that thrives in saturated brines of Maharloo Lake, Iran. Based on its unique combination of morphologic features, its molecular characterization, and its unusual ecology, it is assigned to a newly erected monotypic genus incertae sedis in order Spathidiida. The new species differs from other spathidiids by: a cell with a very short acutely pointed tail, the absence of a circumoral kinety with, instead, inclined, interrupted circumoral kinetofragments at the anterior end of somatic kineties and brush rows abutting the oral bulge, the absence of a contractile vacuole, a heteromorphic dorsal brush comprising five or six rows, and an extreme (at or near saturation) hypersaline habitat. We briefly discuss the persistent uncertainties regarding the phylogenetic relationships within the order Spathidiida.

Engineering osmolysis susceptibility in Cupriavidus necator and Escherichia coli for recovery of intracellular products

BackgroundIntracellular biomacromolecules, such as industrial enzymes and biopolymers, represent an important class of bio-derived products obtained from bacterial hosts. A common key step in the downstream separation of these biomolecules is lysis of the bacterial cell wall to effect release of cytoplasmic contents. Cell lysis is typically achieved either through mechanical disruption or reagent-based methods, which introduce issues of energy demand, material needs, high costs, and scaling problems. Osmolysis, a cell lysis method that relies on hypoosmotic downshock upon resuspension of cells in distilled water, has been applied for bioseparation of intracellular products from extreme halophiles and mammalian cells. However, most industrial bacterial strains are non-halotolerant and relatively resistant to hypoosmotic cell lysis. ResultsTo overcome this limitation, we developed two strategies to increase the susceptibility of non-halotolerant hosts to osmolysis using Cupriavidus necator, a strain often used in electromicrobial production, as a prototypical strain. In one strategy, C. necator was evolved to increase its halotolerance from 1.5% to 3.25% (w/v) NaCl through adaptive laboratory evolution, and genes potentially responsible for this phenotypic change were identified by whole genome sequencing. The evolved halotolerant strain experienced an osmolytic efficiency of 47% in distilled water following growth in 3% (w/v) NaCl. In a second strategy, the cells were made susceptible to osmolysis by knocking out the large-conductance mechanosensitive channel (mscL) gene in C. necator. When these strategies were combined by knocking out the mscL gene from the evolved halotolerant strain, greater than 90% osmolytic efficiency was observed upon osmotic downshock. A modified version of this strategy was applied to E. coli BL21 by deleting the mscL and mscS (small-conductance mechanosensitive channel) genes. When grown in medium with 4% NaCl and subsequently resuspended in distilled water, this engineered strain experienced 75% cell lysis, although decreases in cell growth rate due to higher salt concentrations were observed.ConclusionsOur strategy is shown to be a simple and effective way to lyse cells for the purification of intracellular biomacromolecules and may be applicable in many bacteria used for bioproduction.

Antimicrobial Activity of Extremely Halophilic Archaea Isolated from Southern Thai Salt-Fermented Products and Solar Saltern of Pattani, Thailand

This research aimed to study the diversity and antimicrobial activity of culturable haloarchaea in soil samples of solar saltern in Pattani Province, Thailand and Southern Thai salt-fermented food. Seventy-seven extremely haloarchaea were isolated on Halophilic medium agar containing 25% NaCl at 37°C for 7-21 days. They were grouped by Amplified Ribosomal DNA Restriction Analysis (ARDRA) with two restriction enzymes, RsaI and HindIII. The ARDRA patterns illustrated 6 different Operation Taxonomic Units (OTUs). Partial 16S rRNA gene sequences (938 bp) of the representative of each OTUs were aligned with the GenBank database. The results showed that the representatives of OTU1, OTU2, OTU3, OTU4, OTU5, and OTU6 had 99-100% similarity to Halobacterium salinarum, 99-100% similarity to Halostagnicola larsenii, 99% similarity to Natronococcus sp., 99-100% similarity to Haloferax alexandrinus, 99-100% similarity to Natrialba sp. and 97% similarity to Halococcus sp., respectively. The antimicrobial activity testing of the 17 isolated haloarchaeal strains from solar saltern was performed against 5 tested strains of Hbt. salinarum and 1 strain of Natrialba sp. were isolated from fermented food. Seven (41.2%) were candidate halocin-producing strains. In addition, no phage activity was observed. The 14-day fermentation broth of Natronococcus sp. SS13 showed the highest antimicrobial activity against Hbt. salinarum PK08, BD07 and BD09 (>5,120 AU/ml).

Thrive or survive: prokaryotic life in hypersaline soils

BackgroundSoil services are central to life on the planet, with microorganisms as their main drivers. Thus, the evaluation of soil quality requires an understanding of the principles and factors governing microbial dynamics within it. High salt content is a constraint for life affecting more than 900 million hectares of land, a number predicted to rise at an alarming rate due to changing climate. Nevertheless, little is known about how microbial life unfolds in these habitats. In this study, DNA stable-isotope probing (DNA-SIP) with 18O-water was used to determine for the first time the taxa able to grow in hypersaline soil samples (ECe = 97.02 dS/m). We further evaluated the role of light on prokaryotes growth in this habitat.ResultsWe detected growth of both archaea and bacteria, with taxon-specific growth patterns providing insights into the drivers of success in saline soils. Phylotypes related to extreme halophiles, including haloarchaea and Salinibacter, which share an energetically efficient mechanism for salt adaptation (salt-in strategy), dominated the active community. Bacteria related to moderately halophilic and halotolerant taxa, such as Staphylococcus, Aliifodinibius, Bradymonadales or Chitinophagales also grew during the incubations, but they incorporated less heavy isotope. Light did not stimulate prokaryotic photosynthesis but instead restricted the growth of most bacteria and reduced the diversity of archaea that grew.ConclusionsThe results of this study suggest that life in saline soils is energetically expensive and that soil heterogeneity and traits such as exopolysaccharide production or predation may support growth in hypersaline soils. The contribution of phototrophy to supporting the heterotrophic community in saline soils remains unclear. This study paves the way toward a more comprehensive understanding of the functioning of these environments, which is fundamental to their management. Furthermore, it illustrates the potential of further research in saline soils to deepen our understanding of the effect of salinity on microbial communities.

Abstract 1386: Evolutionary Advantage to Protein Splicing in an Extreme Halophile

Abstract 1386: Evolutionary Advantage to Protein Splicing in an Extreme Halophile

Biosynthesis of Silver Chloride Nanoparticles (AgCl-NPs) fromExtreme Halophiles and Evaluation of Their Biological Applications.

The biosynthesis of nanoparticles (NPs) has gained an overwhelming interest due to their biological applications. However, NPs synthesis by pigmented extreme halophiles remains underexplored. The NPs synthesis using pigmented halophiles is inexpensive and less toxic than other processes. In this study, pigmented halophilic microorganisms (n = 77) were screened to synthesize silver chloride nanoparticles (AgCl-NPs) with silver nitrate as metal precursors, and their biological applications were assessed. The synthesis of AgCl-NPs was possible using the crude extract from cellular lysis (CECL) of six extreme halophiles. Two of the AgCl-NPs viz. AK2-NPs and MY6-NPs synthesized by the CECL of Haloferax alexandrinus RK_AK2 and Haloferax lucentense RK_MY6, respectively, exhibited antimicrobial, antioxidative, and anti-inflammatory activities. The surface plasmon resonance of the AgCl-NPs was determined with UV spectroscopy. XRD analysis of AK2-NPs and MY6-NPs confirmed the presence of silver in the form of chlorargyrite (silver chloride) having a cubic structure. The crystallite size of AK2-NPs and MY6-NPs, estimated with the Scherrer formula, was 115.81nm and 137.50nm. FTIR analysis verified the presence of diverse functional groups. Dynamic light-scattering analysis confirmed that the average size distribution of NPs was 71.02nm and 117.36nm for AK2-NPs and MY6-NPs, respectively, with monodisperse nature. The functional group in 1623-1641cm-1 indicated the presence of protein β-sheet structure and shifting of amino and hydroxyl groups from the pigmented CECL, which helps in capping and stabilizing nanoparticles. The study provides evidence that CECL of Haloferax species can rapidly synthesize NPs with unique characteristics and biological applications.

Natronocalculus amylovorans gen. nov., sp. nov., and Natranaeroarchaeum aerophilus sp. nov., dominant culturable amylolytic natronoarchaea from hypersaline soda lakes in southwestern Siberia

Several pure cultures of alkaliphilic haloaloarchaea were enriched and isolated from hypersaline soda lakes in southwestern Siberia using amylopectin and fructans as substrates. Phylogenomic analysis placed the isolates into two distinct groups within the class Halobacteria. Four isolates forming group 1 were closely related to a recently described Natranaeroarchaeum sulfidigenes and the other three strains forming group 2 represent a novel genus-level phylogenetic lineage. All isolates are saccharolytic archaea growing with various starch-like alpha-glucans including soluble starch, amylopectin, dextrin, glycogen, pullulane and cyclodextrin. In addition, group 1 can use levan while group 2 – inulin (plant storage beta-fructans). Group 1 strains can also grow anaerobically with either glucose or maltose using elemental sulfur as the electron acceptor. Both groups are moderately alkaliphilic with a pH range for growth from 7.2 to 9.3 (optimum between 8.0–8.8) and low Mg-demanding extreme halophiles growing optimally at 4 M total Na+. The major respiratory menaquinone is MK-8:8 and the core biphytanyl lipids are dominated by archaeol (C20-C20) and a less abundant extended archaeol (C20-C25) with PG and PGP-Me as polar groups. The four isolates of group 1 are suggested to be classified into a new species as Natranaeroarchaeum aerophilus sp. nov. (type strain AArc-St1-1T = JCM 32519T). The three isolates of group 2 are proposed to form a new genus and species for which the name Natronocalculus amylovorans gen. nov., sp. nov. is suggested (type strain AArc-St2T = JCM 32475T).

A Directed Evolution Experiment to Improve Protein Splicing of Two Inteins From Haloquadratum walsbyi

We are interested in the protein splicing of the inteins from the extreme halophile Haloquadratum walsbyi. Protein splicing is a post translational process by which an intein excises itself and ligates the two flanking polypeptides, the exteins. Two inteins interrupt the cell division control (cdc21) protein in H. walsbyi. One intein splices only at salt concentrations above 2 M, whereas the other will splice at lower salt concentrations. We have designed a directed evolution experiment coupling the growth of E. coli to successful splicing of each intein from the protein that confers resistance to the antibiotic kanamycin. Preliminary results suggest that each intein can promote splicing of the kanamycin resistance protein, and we are currently testing a pool of intein mutants for enhanced splicing activity.

High Mg/Ca Molar Ratios Promote Protodolomite Precipitation Induced by the Extreme Halophilic Bacterium Vibrio harveyi QPL2.

Bacterial activities have been demonstrated as critical for protodolomite precipitation in specific aqueous conditions, whereas the relationship between the various hydrochemical factors and bacterial activity has not been fully explored. In this study, biomineralization experiments were conducted using a newly isolated extreme halophilic bacterium from salina mud, Vibrio harveyi QPL2, under various Mg/Ca molar ratios (0, 3, 6, 10, and 12) and a salinity of 200‰. The mineral phases, elemental composition, morphology, and crystal lattice structure of the precipitates were analyzed by XRD, SEM, and HRTEM, respectively. The organic weight and functional groups in the biominerals were identified by TG-DSC, FTIR, and XPS analysis. The amounts of amino acids and polysaccharides in the EPS of QPL2 cultured at various Mg/Ca molar ratios were quantified by an amino acid analyzer and high-performance liquid chromatography. The results confirm that disordered stoichiometric protodolomite was successfully precipitated through the activities of bacteria in a medium with relatively high Mg/Ca molar ratios (10 and 12) but it was not identified in cultures with lower Mg/Ca molar ratios (0, 3, and 6). That bacterial activity is critical for protodolomite formation as shown by the significant bacterial relicts identified in the precipitated spherulite crystals, including pinhole structures, a mineral coating around cells, and high organic matter content within the crystals. It was also confirmed that the high Mg/Ca molar ratio affects the composition of the organic components in the bacterial EPS, leading to the precipitation of the protodolomite. Specifically, not only the total EPS amount, but also other facilitators including the acidic amino acids (Glu and Asp) and polysaccharides in the EPS, increased significantly under the high Mg/Ca molar ratios. Combined with previous studies, the present findings suggest a clear link between high Mg/Ca molar ratios and the formation of protodolomite through halophilic bacterial activity.

Adaptation to Varying Salinity in Halomonas elongata: Much More Than Ectoine Accumulation.

The halophilic γ-proteobacterium Halomonas elongata DSM 2581T thrives at salt concentrations well above 10 % NaCl (1.7 M NaCl). A well-known osmoregulatory mechanism is the accumulation of the compatible solute ectoine within the cell in response to osmotic stress. While ectoine accumulation is central to osmoregulation and promotes resistance to high salinity in halophilic bacteria, ectoine has this effect only to a much lesser extent in non-halophiles. We carried out transcriptome analysis of H. elongata grown on two different carbon sources (acetate or glucose), and low (0.17 M NaCl), medium (1 M), and high salinity (2 M) to identify additional mechanisms for adaptation to high saline environments. To avoid a methodological bias, the transcripts were evaluated by applying two methods, DESeq2 and Transcripts Per Million (TPM). The differentially transcribed genes in response to the available carbon sources and salt stress were then compared to the transcriptome profile of Chromohalobacter salexigens, a closely related moderate halophilic bacterium. Transcriptome profiling supports the notion that glucose is degraded via the cytoplasmic Entner-Doudoroff pathway, whereas the Embden-Meyerhoff-Parnas pathway is employed for gluconeogenesis. The machinery of oxidative phosphorylation in H. elongata and C. salexigens differs greatly from that of non-halophilic organisms, and electron flow can occur from quinone to oxygen along four alternative routes. Two of these pathways via cytochrome bo' and cytochrome bd quinol oxidases seem to be upregulated in salt stressed cells. Among the most highly regulated genes in H. elongata and C. salexigens are those encoding chemotaxis and motility proteins, with genes for chemotaxis and flagellar assembly severely downregulated at low salt concentrations. We also compared transcripts at low and high-salt stress (low growth rate) with transcripts at optimal salt concentration and found that the majority of regulated genes were down-regulated in stressed cells, including many genes involved in carbohydrate metabolism, while ribosome synthesis was up-regulated, which is in contrast to what is known from non-halophiles at slow growth. Finally, comparing the acidity of the cytoplasmic proteomes of non-halophiles, extreme halophiles and moderate halophiles suggests adaptation to an increased cytoplasmic ion concentration of H. elongata. Taken together, these results lead us to propose a model for salt tolerance in H. elongata where ion accumulation plays a greater role in salt tolerance than previously assumed.

Biomineralization by Extremely Halophilic and Metal-Tolerant Community Members from a Sulfate-Dominated Metal-Rich Environment.

The adaptation to adverse environmental conditions can lead to adapted microbial communities that may be screened for mechanisms involved in halophily and, in this case, metal tolerance. At a former uranium mining and milling site in Seelingstädt, Germany, microbial communities from surface waters and sediment soils were screened for isolates surviving high salt and metal concentrations. The high salt contents consisted mainly of chloride and sulfate, both in soil and riverbed sediment samples, accompanied by high metal loads with presence of cesium and strontium. The community structure was dominated by Chloroflexi, Proteobacteria and Acidobacteriota, while only at the highest contaminations did Firmicutes and Desulfobacterota reach appreciable percentages in the DNA-based community analysis. The extreme conditions providing high stress were mirrored by low numbers of cultivable strains. Thirty-four extremely halotolerant bacteria (23 Bacillus sp. and another 4 Bacillales, 5 Actinobacteria, and 1 Gamma-Proteobacterium) surviving 25 to 100 mM SrCl2, CsCl, and Cs2SO4 were further analyzed. Mineral formation of strontium- or cesium-struvite could be observed, reducing bioavailability and thereby constituting the dominant metal and salt resistance strategy in this environment.

Ubiquitousness of Haloferax and Carotenoid Producing Genes in Arabian Sea Coastal Biosystems of India

This study presents a comparative analysis of halophiles from the global open sea and coastal biosystems through shotgun metagenomes (n = 209) retrieved from public repositories. The open sea was significantly enriched with Prochlorococcus and Candidatus pelagibacter. Meanwhile, coastal biosystems were dominated by Marinobacter and Alcanivorax. Halophilic archaea Haloarcula and Haloquandratum, predominant in the coastal biosystem, were significantly (p < 0.05) enriched in coastal biosystems compared to the open sea. Analysis of whole genomes (n = 23,540), retrieved from EzBioCloud, detected crtI in 64.66% of genomes, while cruF was observed in 1.69% Bacteria and 40.75% Archaea. We further confirmed the viability and carotenoid pigment production by pure culture isolation (n = 1351) of extreme halophiles from sediments (n = 410 × 3) sampling at the Arabian coastline of India. All red-pigmented isolates were represented exclusively by Haloferax, resistant to saturated NaCl (6 M), and had >60% G + C content. Multidrug resistance to tetracycline, gentamicin, ampicillin, and chloramphenicol were also observed. Our study showed that coastal biosystems could be more suited for bioprospection of halophiles rather than the open sea.

Complete Genome Sequence of an Extremely Halophilic Archaeon from Great Salt Lake, Halobacterium sp. GSL-19.

ABSTRACTAn extremely halophilic archaeon, Halobacterium sp. GSL-19, was isolated from the north arm of Great Salt Lake in Utah. Single-molecule real-time (SMRT) sequencing was used to establish a GC-rich 2.3-Mbp genome composed of a circular chromosome and 2 plasmids, with 2,367 predicted genes, including 1 encoding a CTAG-methylase widely distributed among Haloarchaea.

Extremely Halophilic Biohydrogen Producing Microbial Communities from High-Salinity Soil and Salt Evaporation Pond

Extreme halophiles offer the advantage to save on the costs of sterilization and water for biohydrogen production from lignocellulosic waste after the pretreatment process with their ability to withstand extreme salt concentrations. This study identifies the dominant hydrogen-producing genera and species among the acclimatized, extremely halotolerant microbial communities taken from two salt-damaged soil locations in Khon Kaen and one location from the salt evaporation pond in Samut Sakhon, Thailand. The microbial communities’ V3–V4 regions of 16srRNA were analyzed using high-throughput amplicon sequencing. A total of 345 operational taxonomic units were obtained and the high-throughput sequencing confirmed that Firmicutes was the dominant phyla of the three communities. Halanaerobium fermentans and Halanaerobacter lacunarum were the dominant hydrogen-producing species of the communities. Spatial proximity was not found to be a determining factor for similarities between these extremely halophilic microbial communities. Through the study of the microbial communities, strategies can be developed to increase biohydrogen molar yield.

Both pH and salinity shape the microbial communities of the lakes in Badain Jaran Desert, NW China

Badain Jaran Desert (BJD), characterized by extremely arid climate and tallest sand dunes in the world, is the second largest desert in China. Surprisingly, there are a large number of permanent lakes in this desert. At present, little is known about the composition and distribution of microbial communities in these desert lakes, which are an important bioresource and play a fundamental role in the elemental cycles of the lakes. In this study, the physicochemical characteristics and microbial communities of water samples from 15 lakes in BJD were comparatively investigated. The results showed that the lakes were rich in Na+, Cl−, CO32− and HCO3− while Ca2+ and Mg2+ were scarce, with pH 8.52–10.27 and salinity 1.05–478.70 g/L. Bacteria dominated exclusively in low saline lakes (salinity < 50 g/L) while archaea were predominant in hypersaline lakes (salinity > 250 g/L), which abundance increased along salinity gradient linearly. Genera Flavobacterium, Synechocystis and Roseobacter from phyla Bacteroidetes, Cyanobacteria, Alphaproteobacteria were the major members in low saline lakes whereas Halomonas, Aliidiomarina and Halopelagius from Gammaproteobacteria and Euryarchaeota were abundant in moderately saline lakes (salinity 50–250 g/L). The hypersaline lakes were predominated by extreme halophiles such as Halorubrum, Halohasta and Natronomonas from Euryarchaeota. The correlation among the microbes in the lakes was mainly positive, suggesting they can survive in the harsh environments through synergistic interactions. Statistical analyses indicated that physicochemical characteristics rather than spatial factors shaped the microbial communities in the desert lakes. The pH was the most important environmental factor controlling alpha diversity, while salinity was the major driver determining microbial community structure in BJD lakes. In contrast, geographic factors had no significant impact on the microbial community compositions.

Genome Sequence of Hardyhisp2, a Gammapleolipovirus Infecting Haloarcula hispanica.

Hardyhisp2 virus infects the halophilic archaeon Haloarcula hispanica DSM 4426T and is closely related to His2 (Pleolipoviridae family). The viral genome is 16,133 bp long, with terminal inverted repeats of 599 bp. The predicted spike protein is only weakly similar (32% amino acid identity) to that of His2.