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At least 19 recordsLinked to original sources
PubMed1990

Formation and breakdown of glycine betaine and trimethylamine in hypersaline environments.

Glycine betaine is accumulated as a compatible solute in many photosynthetic and non-photosynthetic bacteria--the last being unable to synthesize the compound--and thus large pools of betaine can be expected to be present in hypersaline environments. A variety of aerobic and anaerobic microorganisms degrade betaine to among other products trimethylamine and methylamine, in a number of different pathways. Curiously, very few of these betaine breakdown processes have yet been identified in hypersaline environments. Trimethylamine can also be formed by bacterial reduction of trimethylamine N-oxide (also by extremely halophilic archaeobacteria). Degradation of trimethylamine in hypersaline environments by halophilic methanogenic bacteria is relatively well documented, and leads to the formation of methane, carbon dioxide and ammonia.

Betaine↗
PubMed2026

Sulfide-oxidizing potential and hypersalinity tolerance strategies in salt-crust covered coastal microbial mats.

Hypersaline microbial mats are dense microbial ecosystems capable of performing nearly complete element cycling under harsh conditions including near-saturation salinity. Our previous study of salt-crust-covered microbial mats showed that oxygenic photosynthesis was inhibited at salt saturation, while phototrophic sulfide oxidation persisted despite well-known sulfide-oxidizing taxa being undetectable. In this study, we analyzed metagenome-assembled genomes (MAGs) from the same mats to identify sulfide-oxidizing taxa and adaptations enabling oxygenic phototrophs to survive salt saturation. We extended the dataset by including morphologically identical mats exposed to lower salinity regimes to identify metabolic capabilities specifically selected for by saturation-level salinity. The phototrophic sulfide oxidation capability was found in nearly all cyanobacterial MAGs, in some Chloroflexota, and in abundant Rhodovibrio populations previously not known to oxidize sulfide. Furthermore, we found clear indications of Haloarchaea-like potassium-based osmoregulation in Bradymonadaceae (Myxococcota) adding another taxon to the few known potassium-accumulating bacteria. Despite lower oxygen concentrations, salt-crust-covered mats showed smaller proportions of fermenters and higher proportions of aerobic microorganisms than lower-salinity mats. We compared the genetic signatures of hypersalinity and desiccation tolerance in cyanobacterial MAGs from this study to genomes from desiccation-prone environments such as desert soils and small freshwater streams. Genomes of hyperhalophilic cyanobacteria were characterized by lack of certain potassium transporters and catalase genes and presence of additional osmolyte transporter subunits and sulfide-oxidation genes. We hypothesize that during salt saturation the oxidative stress for mat dwelling cyanobacteria is lowered, while the ability to oxidize sulfide provides them with energy when oxygenic photosynthesis is inhibited.

Oxidation-Reduction↗
PubMed1977

The pituitary of Aphanius dispar (Rüppell) from hypersaline marshes and freshwater. II. Ultrastructure of the rostral pars distalis.

An ultrastructural study of the rostral pars distalis of the pituitary of Aphanius dispar specimens taken from freshwater or hypersaline marshes revealed significant structural differences which indicate higher activity of the prolactin cells in the hypotonic medium. Prolactin cells from freshwater specimens had larger secretory granules, a higher amount of endoplasmic reticulum, and expanded intercellular spaces with many secretory lakes. These cells contained an unusual cytoplasmic structure, consisting of twisted canals with vesicular lumina, connected to the endoplasmic reticulum of the cell. This structure is about 1-2 micron in diameter. Stellate cells are characterized by extracellular spacing junctions which are particularly noticeable at the confluence of the interstellate cell canaliculi and the pericapillary space.

Animals↗
PubMedDate not supplied

[Number of bacteria and features of their activity in hypersaline reservoirs of the Crimea].

The incidence of bacteria, their biomass production, and heterotrophic assimilation of CO2 by bacterioplankton were studied in the Crimean hypersaline water reservoirs from May to October of 1974. The total incidence of bacteria in the natural brine of these reservoirs varied from 20 to 70 x 10(6) cells per 1 ml. Such a high bacterial number may be caused by the combined action of water evaporation which increased the concentration of bacterial cells and active growth of microflora. Low values of bacterial production and heterotrophic CO2 assimilation should be attributed to weak activity of microflora in the reservoirs.

Seasons↗
PubMed2026

Comparative metagenomic analysis of microbial communities: unravelling microbial communities from the great Rann of Kachchh and coastal saltpans, Gujarat, India.

Hypersaline environments exhibit extreme physiochemical conditions yet support diverse microbial communities. These communities are not only ecologically important but also possess substantial potential for biotechnological exploitation. In this study, we employed a comparative metagenomic approach to assess microbial diversity using two distinct methodologies: (1) direct DNA extraction from raw sediment, and (2) DNA extraction following halophilic enrichment in selective media. Sediment samples were collected from multiple sites and pooled together within the Rann of Kachchh and close-by saltpans and were analysed using 16S rRNA sequencing coupled with bioinformatics pipelines. The results revealed pronounced differences in microbial community composition between the two approaches. Raw sediment samples exhibited significantly higher alpha diversity, with dominant taxa including Halobacterota, Cyanobacteria, and Desulfobacterota, with a substantial proportion of unclassified genera. In contrast, enriched samples were dominated by fast-growing, culturable genera such as Halobacterium, Alkalibacillus, and Candidatus haloredivivus. Principal Coordinate Analysis (PCoA) of beta diversity demonstrated distinct clustering between raw and enriched communities, even within samples from the same sites, underscoring the selective bias introduced by enrichment procedures. These findings emphasise that the methodological choice strongly influences the observed microbial diversity. The aim of this study was to compare microbial community composition in raw hypersaline sediments and enrichment cultures using metagenomic sequencing, to evaluate how enrichment selectively favours specific halophilic taxa. This comparative approach allows identification of the microbial groups that rapidly proliferate under controlled hypersaline conditions, thereby complementing direct environmental sequencing. By integrating both direct and enrichment-based metagenomic approaches, a more comprehensive understanding of microbial community structure in hypersaline environments can be achieved.

India↗
PubMed2026

Phylogeographic analysis of Staphylococcus nepalensis reveals global occurrence of antimicrobial-resistant lineages carrying the sal(E) resistance gene.

BACKGROUND: Staphylococcus nepalensis is an emerging species first described in 2003 from the respiratory tract of goats in Nepal. We report the identification of S. nepalensis of a hypersaline lagoon in Brazil, along with in-depth phylogeographical and resistome analysis of publicly available genomes. METHODS AND RESULTS: During a local survey from hypersaline aquatic environments in Rio de Janeiro, Brazil, two staphylococcal strains were recovered, designated as COLB and AM1. These isolates were subjected to antimicrobial susceptibility testing, genomic sequencing, and comprehensive phylogenomic analyses. Genomic analysis confirmed the taxonomic identity of COLB and AM1 as S. nepalensis. Both isolates harbored the sal(E) conferring resistance to pleuromutilins and streptogramin A, whereas tet(K) conferring to tetracyclines. Additionally, AM1 carried lnu(A), consistent with the reduced susceptibility to clindamycin (MIC = 2 µg/mL) relative to COLB. Genes associated with arsenic and copper tolerance, and the replicons rep7a and rep19c, were confirmed. Phylogenomic analysis indicated that COLB and AM1 were clonally related (1 cgSNP-difference) but distinct from global isolates. Phylogeographic analysis revealed wide geographic occurrence, with some lineages carrying blaZ and mecA associated with beta-lactamase production and methicillin resistance, respectively. Strikingly, sal(E) is conserved across all S. nepalensis genomes. CONCLUSIONS: The findings confirm the presence of S. nepalensis in South America as early as 2016 and documented among available genomes from environmental, human, and animal-associated sources. Furthermore, reveal the circulation of some lineages carrying clinically relevant antimicrobial genes, underscoring the importance of accurate species identification and continuous genomic surveillance and potential One Health relevance.

Phylogeography↗
PubMed1988

Anaerobic degradation of organic compounds at high salt concentrations.

A number of obligately anaerobic fermentative bacteria are known to degrade a variety of organic substrates such as sugars, amino acids, and others, in the presence of high salt concentrations (up to 3-4 M) to products such as hydrogen, CO2, acetate and higher fatty acids, and ethanol. Our understanding of the fate of these products in hypersaline environments is still extremely limited. The occurrence of bacterial sulfate reduction is well established at salt concentrations of up to 24%; however, the bacteria involved have not yet been isolated in pure culture, and the range of electron donors used is unknown. Halophilic or halotolerant methanogenic bacteria using hydrogen/CO2 or acetate as energy source are notably absent; methanogenesis under hypersaline conditions is probably limited to such substrates as methanol and methylamines, which cannot be expected to be major products of anaerobic degradation of most organic compounds.

Bacteria, Anaerobic↗
PubMed2026

Genome-scale insights into metabolic streamlining and photosynthetic energy balance in the extremophile green alga Picocystis salinarum (Picocystophyceae, Chlorophyta).

Picocystis salinarum is an early-diverging chlorophyte and the sole described member of the Picocystophyceae, frequently dominating hypersaline and alkaline lakes despite extreme physicochemical constraints. To elucidate the genomic foundations of its ecological success, we generated a fully annotated, chromosome-scale nuclear genome assembly of the type strain originally isolated from a saline pond in San Francisco Bay. The 18.5-Mb genome comprises 30 chromosomal assemblies, exhibits clear diploidy, and contains multiple copies of intact Ty3/Gypsy and Ty1/Copia long terminal repeat retrotransposons encoding polyproteins with atypical accessory domains. Phylogenomic analyses reveal strong affinity with the Nephroselmidophyceae. Comparative analyses reveal extensive metabolic streamlining, including the absence of a queuosine salvage pathway, the 2-methylcitrate cycle, β-oxidation of propionate, and branched-chain amino acid catabolism, traits retained in several marine prasinophyte lineages. In contrast, the genome preserves multiple ancestral bacterial derived systems. Notably, P. salinarum features a complete chloroplast NADH dehydrogenase-like complex, including all membrane, electron binding, and assembly components, a configuration not previously reported in sequenced chlorophyte algae. This retention implies substantial capacity for cyclic electron flow and chlororespiration, processes expected to be critical in chronically low-light and chemically extreme environments. The genome further reveals a distinctive biochemical CO2-concentrating mechanism centered on plastid-targeted phosphoenolpyruvate carboxykinase, complete plastid peptidoglycan biosynthetic and remodeling pathways, and partial retention of lipid-A-related machinery. Conversely, P. salinarum lacks canonical non-photochemical quenching proteins while retaining xanthophyll-cycle enzymes that support slower photoprotective responses. Together, these features define a coordinated genomic architecture that underpins the specialization of P. salinarum to hypersaline, alkaline, and persistently low-light ecosystems.

3‐deoxy‐D‐manno‐octulo↗
PubMed2026

The halophilic archaeon Halogranum roseipondis sp. nov. is susceptible to a virus carrying an exceptionally high number of viral tRNA genes.

UNLABELLED: Archaea constitute a diverse group of organisms, many of which inhabit extreme environments, such as haloarchaea that dominate hypersaline ecosystems, like solar salterns. Sampling of solar salterns and other hypersaline environments has resulted in numerous haloarchaeal isolates, including 3 classified and 27 uncharacterized Halogranum species. However, no complete genome has so far been reported for any member of this genus. Here, we present the first comprehensive study of Halogranum sp. SS5-1 isolated from a solar saltern in Samut Sakhon, Thailand. Hgn. SS5-1 is a pleomorphic, aerobic heterotroph that thrives in high salinity and moderate temperature and is capable of hydrolyzing starch. Its genome consists of a 3.6 Mbp chromosome and seven additional plasmids. Based on our phylogenetic analyses, which establish Hgn. SS5-1 as a distinct species, we propose that it will be classified as the novel species Halogranum roseipondis sp. nov. SS5-1T. Additionally, we report that Hgn. roseipondis sp. nov. SS5-1T is infected by Hagravirus capitaneum (HGTV-1), the only virus known to infect a Halogranum host. HGTV-1 exhibits a unique head-tailed morphology and encodes the largest archaeal virus double-stranded DNA genome known to date, including 34 tRNA-encoding genes. Codon usage analysis of the viral genome suggests partial alignment with host preferences, yet the abundance of viral tRNA genes hints at broader roles, potentially including roles in translation and host regulation. This study establishes Hgn. roseipondis and HGTV-1 as a novel virus-host system, opening avenues to explore infection dynamics and the roles of virus-encoded tRNA in archaea. IMPORTANCE: Archaea that thrive in high-salinity environments are key players in geochemical cycles and important contributors to ecosystem productivity. Despite their ecological significance and importance for the development of novel methodologies in synthetic biology, haloarchaea remain poorly studied. Further exploration of haloarchaea is required to obtain valuable information on the evolution of cellular complexity and the molecular mechanisms that allow cells to thrive in harsh environmental conditions. Here, we present the characterization of a novel archaeon, Halogranum roseipondis sp. SS5-1T, alongside the infection cycle of its associated virus, Hagravirus capitaneum. This tailed myovirus carries an extraordinary set of 34 viral tRNA genes, a feature that opens intriguing questions about virus-host interactions and translational control. Our findings lay the groundwork for future investigations into the expression and function of viral tRNAs in an archaeal model system, thereby opening a new frontier for studying archaeal translation and virus-driven modulation of host cellular processes.

Halobacteriaceae↗
PubMed1991

Sublethal effects of pentachlorophenol in the abalone (Haliotis rufescens) as measured by in vivo 31P NMR spectroscopy.

The sublethal biochemical effects of pentachlorophenol (PCP) were investigated in live, intact red abalones (Haliotis rufescens), using a flow-through exposure system, by in vivo 31P NMR spectroscopy. Based on rangefinding tests (6-hr LC50 = 1.6 mg/L; 6-hr no-observable-effect-level (NOEL) = 0.8 mg/L), three abalones were separately exposed to a sublethal concentration (1.2 mg/L) for 5 hr, followed by a 13 hr recovery period. Effects in foot muscle included both a decrease in phosphoarginine and an increase in inorganic monophosphate concentrations ([PA] and [Pi], respectively); both foot muscle concentrations of adenosine triphosphate [ATP] and intracellular pH (pHi) also declined. Parallel in vitro experiments revealed that concentrations of glycerol 3-phosphate, lactate, citrate, succinate, malate, and alanine (Ala) all increased, while those of glyceraldehyde 3-phosphate and glutamine (Gln) remained stable. Also, these effects were not evident until 2 hr into exposure, possibly the time required for PCP to attain an effective concentration in foot muscle. During recovery, while Pi declined to pre-exposure levels, [PA] completely recovered in only one individual. Also, realkalinization of pHi was similar to recovery of [Pi], and ATP returned to near-initial levels, as did glycerol 3-phosphate, lactate, succinate, malate, and Ala; glyceraldehyde 3-phosphate, citrate, and Gln levels declined. Recovery responses corresponded to the time for PCP clearance from foot muscle. The effects of PCP were similar to those of hypoxia, fatigue, hypersalinity, and arginine kinase inhibitors, and so sublethal PCP concentrations may also inhibit electron transport and arginine kinase as well as uncouple mitochondrial oxidative phosphorylation in intact molluscs. Thus, the effects of pollutants on key biochemical processes may now be measured in intact aquatic organisms as they occur, improving our ability to accurately assess the environmental effects of pollutants in the laboratory.

Animals↗
PubMed1979

An ultraviolet light induced bacteriophage in Beneckea gazogenes.

An ultraviolet light induced prophage has been discovered in the red pigmented marine vibrio Beneckea gazogenes. Two spontaneously derived pigment mutants, one forming pink colonies and one lacking pigment and forming white colonies, were also irradiated. The presence of pigment was not related to phage induction; uv-induced cell lysis occurred in wildtype and mutant strains at the same dosages. Lysis was not prevented or retarded by exposure after irradiation to visible light indicating the phenomenon was not photoreactivable. Electron micrographs of the 'T-like' B. gazogenes phage are shown. A second beneckea was isolated form the anaerobic zone of cyanobacterial mats growing in the hypersaline environment of Laguna Mormona, Baja California. The Baja beneckea does not harbor a uv inducible prophage and is resistant to the B. gazogenes phage under all conditions tested.

Bacteriolysis↗
PubMed1988

Glycinebetaine as an osmoregulant and compatible solute in the marine cyanobacterium Spirulina subsalsa.

Glycinebetaine was found to be the major organic substrate accumulating under hypersaline growth conditions in the halotolerant cyanobacterium Spirulina subsalsa. In addition to its proposed role as osmolite, glycinebetaine is shown to specifically protect enzymatic activity. Glucose-6-phosphate dehydrogenase from S. subsalsa retained full activity in the presence of NaCl at concentrations as high as 1.5 M, provided that comparable concentrations of glycinebetaine were also present in the reaction mixture. A kinetic analysis indicated that glycinebetaine protected the enzyme against both NaCl-induced decrease in Vmax and reduction in affinity to glucose 6-phosphate. The alternative osmolites, glycerol and proline, protected the enzyme against the reduction in Vmax but not against the reduction in affinity to glucose 6-phosphate.

Betaine↗
PubMed1990

Polar lipids of non-alkaliphilic Halococci.

Until recently, only one species of Halococcus has been recognized, namely, H. morrhuae, but a large number of extremely halophilic non-alkaliphilic cocci have now been isolated from hypersaline habitats in Spain and classified into four phenons (A-D); one of the phenon D strains has been classified as a new species, Halococcus saccharolyticus. Examination of the lipids of H. saccharolyticus and four strains of phenons A-C showed the presence in all of them of C20-C20 and C20-C25 diether molecular species of phosphatidylglycerophosphate (PGP), phosphatidylglycerol (PG) and phosphatidic acid (PA); a monounsaturated isoprenoid C20-C20 (phytanyl-phytenyl) species of PGP; a sulfated diglycosyl diphytanylglycerol (S-DGD) with structure 2,3-diphytanyl-1-(6-HSO3-mannosyl-1-2-glucosyl)-glycerol, which is identical to the S-DGD-1 in Haloferax mediterranei; a phosphoglycolipid (P-TGD) tentatively identified as a phytanyl-phytenyl-(H2PO3-galactosyl-mannosyl-glycosyl)-glyce rol, and two unidentified glycolipids present only in traces. No phosphatidylglycerosulfate (PGS) was detected in any of the strains examined. This pattern of lipids appears to be characteristic of the strains of Halococcus from salterns in Spain, but studies of a larger number and variety of Haloccus are necessary to establish this conclusion with certainty.

Glycolipids↗
PubMed1989

Relationships among Vibrio costicola strains assessed by DNA-DNA hybridization.

Deoxyribonucleic acid (DNA)-DNA hybridization was used to determine the relationships among 14 strains of Vibrio costicola isolated from cured meats or hypersaline waters. Our results indicate that the strains investigated should be considered members of the same genomic species, with homologies of 60% or higher with the V. costicola strains used as reference. Low DNA relatedness was found with other marine vibrios or moderately halophilic bacteria tested. The guanine-plus-cytosine base contents of DNAs from the 14 V. costicola strains were 47.6 to 51.1 mol%.

Base Composition↗
PubMed2025

A deep metagenomic atlas of Qinghai-Xizang Plateau lakes reveals their microbial diversity and salinity adaptation mechanisms.

The Qinghai-Xizang Plateau (QXP), harboring the planet's highest density of plateau lakes, offers an exceptional biogeographic environment for studying extremophilic microbial communities and their adaptation to salinity. Through deep metagenomic sequencing, we construct the Qinghai-Xizang Lake Sediment Genome (QXLSG) catalog, a high-resolution genomic catalog comprising 5,866 metagenome-assembled genomes (MAGs), 58.16 million non-redundant protein encoding genes, and 19,008 biosynthetic gene clusters. Notably, 80.78% of the 2,742 species-level MAGs represent undescribed taxa, significantly expanding the known microbial diversity. Salinity emerges as the primary environmental factor influencing microbial community. Functional annotation highlights that the "salt-out" strategy, particularly the uptake of glycine betaine, is the main mechanism for salinity tolerance. This strategy is prevalent in both hypersaline lake communities and the dominant microbial phyla. Overall, this study provides a crucial genetic resource for future bioprospecting and deepens our understanding of the fundamental mechanisms of microbial adaptation to extreme saline environments.

Lakes↗
PubMed2024

Multi-omics association study of hexadecane degradation in haloarchaeal strain Halogranum rubrum RO2-11.

Haloarchaea with the capacity to degrade alkanes is promising to deal with petroleum pollution in hypersaline environments. However, only a limited number of haloarchaeal species are investigated, and their pathway and mechanism for alkane degradation remain unclear. In this study, Halogranum rubrum RO2-11, a haloarchaeal strain, verified the ability to degrade kerosene and hexadecane in 184 g/L NaCl, with 53% and 52% degradation rates after 9 and 4 days, respectively. Genome sequencing and gene annotation indicated that strain RO2-11 possesses a complete potential alkane-degrading pathway, of which alkane hydroxylases may include CYP450, AlmA, and LadA. Transcriptome and metabolome analyses revealed that the upregulation of related genes in TCA cycle, lysine biosynthesis, and acetylation may help improve hexadecane degradation. Additionally, an alternative degrading pathway of hexadecane based on dual-terminal β-oxidation may occur in strain RO2-11. It is likely to be the first report of alkane degradation by the genus Halogranum, which may be helpful for applications of oil-pollution bioremediation under high-salt conditions.

Alkanes↗
PubMed1979

Affinity chromatography at sub-zero temperatures. A model study with porcine pancreatic elastase.

A new variety of affinity chromatography of enzymes is described which consists of building up an affinity adsorbent composed of a real substrate. The chromatography is performed at a sub-zero temperature where the turnover of the enzyme is very low or stopped. As a model system Sepharose-bound L-trialanine p-nitroanilide was for used the affinity binding of porcine pancreatic elastase, which was adsorbed to the column in a hypersaline medium at--14 degrees and eluted from the column at the same temperature using 50% (v/v) ethylene glycol. The affinity adsorbent proved to be vary specific as it did not retain trypsin, chymotrypsin and ovalbumin and retained only 20% of cytochrome c.

Animals↗