Saline Habitats Research Articles

Salinity variation modulates cellular stress response to ZnO nanoparticles in a sentinel marine bivalve, the blue mussel Mytilussp.

Zinc oxide nanoparticles are released into marine environments from industrial, medical and consumer uses sparking concerns about their potential ecotoxicological effects. Ecological hazard assessment of nZnO in marine ecosystems is hindered by the lack of understanding of the potential interactive effects of nZnO toxicity with other common abiotic stressors, such as salinity fluctuations, in marine organisms. To close this gap in our knowledge, we carried out a comprehensive biomarker-based assessment of the combined effects of salinity and nZnO in a sentinel marine bivalve, the blue mussels Mytilus edulis. The mussels were exposed for 21 days to clean seawater (control), an environmentally relevant concentration (100 μg Zn l−1) of nZnO or dissolved Zn (to identify the toxic effects attributable to Zn2+ toxicity) under the normal (15), low (5) and fluctuating (5–15) salinity regimes. The selected molecular and biochemical markers focused on the oxidative stress, apoptosis, detoxification system and inflammation in the gills and the digestive gland of the mussels. Biomarker analysis showed different effects of nZnO and dissolved Zn on biomarkers of oxidative stress, xenobiotic detoxification and apoptosis but similar effects of both pollutants on the levels of metallothioneins and inflammatory markers. Exposure to nZnO led to elevated levels of lipid peroxidation, upregulation of p53 and p38 stress kinases and apoptosis-related genes, most notably in the gills. Exposure to dissolved Zn led to accumulation of protein carbonyls and activated redox-sensitive detoxification enzymes (NADPH-P450 reductase and glutathione-S-transferase) in the mussels. The ambient salinity had significant effects the cellular adverse effects of nZnO in the mussels. The nZnO-induced cellular stress was detectable under the normal (15) and fluctuating (5–15) salinity conditions in the studied brackish water population of the mussels. At low salinity (5), nZnO toxicity signal was almost completely dampened. These findings indicate that chronic osmotic stress close to the tolerance limits of M. edulis prevails over the effects of the environmentally relevant nZnO and dissolved Zn concentrations in combined exposures. These stressor interactions might ameliorate the cellular toxicity of nZnO in the mussels but limit applicability of cellular stress biomarkers for detecting the toxic effects of nanopollutants in low salinity habitats.

A Comparative Study on the Buoyancy of Resting Eggs from Different Artemia Populations, with Emphasis on Its Relationships with Habitat Salinity and Biometric Characters of Resting Eggs

A Comparative Study on the Buoyancy of Resting Eggs from Different Artemia Populations, with Emphasis on Its Relationships with Habitat Salinity and Biometric Characters of Resting Eggs

A Comment on: Migrating silver eels return from the sea to the river of origin after a false start (2021) by Tambets M et al.

A Comment on: Migrating silver eels return from the sea to the river of origin after a false start (2021) by Tambets M et al.

Protected species in grassland habitats of Ukraine

Based on the analysis of more than 17,000 vegetation plots (relevés), the participation of 261 protected species (254 vascular plants, six lichens, and one bryophyte) in 30 EUNIS grassland habitat types was revealed. Vegetation plots were assigned to the habitat types using the EUNIS-ESy expert system with further verification. We consider as protected species those listed in the current edition of the Red Data Book of Ukraine, Resolution 6 of the Bern Convention, Annexes II and IV of the Habitat Directive, and the IUCN Red List (only categories VU, EN, CR). The participation of protected species was studied according to the following three criteria: (1) the total number of protected species in the plots assigned to a certain habitat type, (2) the number of plots in which at least one protected species is present, and (3) the mean number of protected species per plots within each habitat type. True steppes (R1B) and meadow steppes (R1A) differed with a significant predominance of the total number of protected species. Arctic alpine calcareous grassland (R44) and Continental dry rocky steppic grassland and dwarf scrub on chalk outcrops (R15) had the largest proportion of plots with protected species and the highest mean numbers of protected species per relevé. Saline habitats, in particular Temperate inland salt marsh (R63) and Semi desert salt pan (R64), were characterized by the smallest number of plots with protected species. Among all species, Gymnadenia conopsea, Stipa capillata, Colchicum autumnale and Gladiolus imbricatus occurred in the largest number of studied habitat types. Based on the results of the analysis, appropriate ways of optimizing the protection of grassland habitats and protected species are proposed.

Evaluation of Halophyte Biopotential as an Unused Natural Resource: The Case of Lobularia maritima.

Halophytes are plant species widely distributed in saline habitats, such as beaches, postindustrial wastelands, irrigated lands, salt flats, and others. Excessive salt level, known to limit plant growth, is not harmful to halophytes, which have developed a variety of defense mechanisms allowing them to colonize harsh environments. Plants under stress are known to respond with several morpho-anatomical adaptations, but also to enhance the production of secondary metabolites to better cope with difficult conditions. Owing to these adaptations, halophytes are an interesting group of undemanding plants with a high potential for application in the food and pharmaceutical industries. Therefore, this review aims to present the characteristics of halophytes, describe changes in their gene expression, and discuss their synthesized metabolites of pharmacognostic and pharmacological significance. Lobularia maritima is characterized as a widely spread halophyte that has been shown to exhibit various pharmacological properties in vitro and in vivo. It is concluded that halophytes may become important sources of natural products for the treatment of various ailments and for supplementing the human diet with necessary non-nutrients and minerals. However, extensive studies are needed to deepen the knowledge of their biological potential in vivo, so that they can be introduced to the pharmaceutical and food industries.

Research Article: Development of the Control System for Artificial Reproduction of Fish Populations Based on a Complex of Neroendocrinological Research and Biotech Innovations

The participation of the hypothalamic-hypophysial neurosecretory system (HHNS) in fish reproduction using light, electron microscopy and immunocytochemistry was established by ecologo-histophysiological studies for the first time in the world literature. At the beginning of passing fish migrations a violation of the HHNS basic osmoregulative function, causing habitat change is revealed. Simultaneously the HHNS causes the neurotropic effect on the central nervous system (CNS) arousal in the form of a dominant state of "Migration impulse." At the beginning of spawning, HHNS also initiates spawning behavior and completes it by participating in the body's protective-adaptive reactions to natural physiological stress. The functional role of the HHNS in fish reproduction is to initiate energy-intensive (reproductive) processes of migratory and spawning behaviors and to complete spawning by suppressing the hyperactivity of target glands, which ensures the body's transition to energy-saving plastic exchange. The analysis of the key role of the HHNS in the integration of fish reproduction by the self-regulation principle has allowed the development of a constructive working scheme. New biotech methods of managing breeding time, rates of survival and growth of valuable fish species were developed on this basis. They are presented in the form of 10 inventions. To stimulate sex maturation, drugs of isolated anterior and posterior pituitary lobes were developed and introduced in sturgeon industry, increasing the extent of their fish-breeding use by 15% and saving the pituitary up to 40%. To delay puberty, a method of industrial fish breeders reservation in the critical salinity habitat of 4-8‰, both in seawater and in table salt solutions has been developed. On this basis, a full-system method of sturgeon and salmon fish populations reproduction, covering all stages of farm biotechnology has been developed. It is carried out by mass breeders reservation in sea cages, obtaining there offspring and, after the river fish-farm growing youngs to their readiness for migration, the final cultivation them in sea cages gardens till large life-resistant youngs. For the implementation of the proposed industrial biotechnology and year-round fish farming a new installation of recirculating aquaculture systems (RAS) hatcheries and farms was developed by means of the off-season underground conditioning of fish cultivation habitat and by the principle of natural-industrial engineering ecology. Due to the general aim ‒ increasing the efficiency biotechnology of reproduction and logical relationships, all developments are integrated into the system of biotech management of fish population reproduction.

Review Article: Systemic Lupus Erythematosus in Gynecology

The participation of the hypothalamic-hypophysial neurosecretory system (HHNS) in fish reproduction using light, electron microscopy and immunocytochemistry was established by ecologo-histophysiological studies for the first time in the world literature. At the beginning of passing fish migrations a violation of the HHNS basic osmoregulative function, causing habitat change is revealed. Simultaneously the HHNS causes the neurotropic effect on the central nervous system (CNS) arousal in the form of a dominant state of "Migration impulse." At the beginning of spawning, HHNS also initiates spawning behavior and completes it by participating in the body's protective-adaptive reactions to natural physiological stress. The functional role of the HHNS in fish reproduction is to initiate energy-intensive (reproductive) processes of migratory and spawning behaviors and to complete spawning by suppressing the hyperactivity of target glands, which ensures the body's transition to energy-saving plastic exchange. The analysis of the key role of the HHNS in the integration of fish reproduction by the self-regulation principle has allowed the development of a constructive working scheme. New biotech methods of managing breeding time, rates of survival and growth of valuable fish species were developed on this basis. They are presented in the form of 10 inventions. To stimulate sex maturation, drugs of isolated anterior and posterior pituitary lobes were developed and introduced in sturgeon industry, increasing the extent of their fish-breeding use by 15% and saving the pituitary up to 40%. To delay puberty, a method of industrial fish breeders reservation in the critical salinity habitat of 4-8‰, both in seawater and in table salt solutions has been developed. On this basis, a full-system method of sturgeon and salmon fish populations reproduction, covering all stages of farm biotechnology has been developed. It is carried out by mass breeders reservation in sea cages, obtaining there offspring and, after the river fish-farm growing youngs to their readiness for migration, the final cultivation them in sea cages gardens till large life-resistant youngs. For the implementation of the proposed industrial biotechnology and year-round fish farming a new installation of recirculating aquaculture systems (RAS) hatcheries and farms was developed by means of the off-season underground conditioning of fish cultivation habitat and by the principle of natural-industrial engineering ecology. Due to the general aim ‒ increasing the efficiency biotechnology of reproduction and logical relationships, all developments are integrated into the system of biotech management of fish population reproduction.

River Discharge Mediates Extent of Phytoplankton and Harmful Algal Bloom Habitat in the Columbia River Estuary (USA) During North Pacific Marine Heat Waves

Marine heat waves (MHWs) have been associated with extensive harmful algal blooms (HABs) in the northeast Pacific Ocean, but the degree to which these large-scale oceanographic events are mirrored in nearshore environments has not been well established. We compared phytoplankton assemblages in the Lower Columbia River Estuary (LCRE) during two Pacific MHWs that took place in 2015 and 2019, with observations from 2017, a year with no MHW. These data were paired with environmental data from the summers of 2015–2019 to characterize differences in estuarine conditions during MHWs that promote phytoplankton assemblage transitions and identify HAB-conducive conditions. Bloom densities of HAB taxa, Pseudo-nitzschia spp. (4.16 × 106 cells L−1) and Gymnodinium catenatum (5.66 × 106 cells L−1), were noted in the estuary during 2015 and 2019, respectively, 2 years where Pacific MHWs occurred during the summer months. These blooms coincided with estuary temperatures that were 1–2 ℃ above and river discharge volumes 46–48% lower than decadal daily averages. We identified patterns in the densities of several algal taxa associated with MHW-mediated low discharge in the LCRE, such as declines in tychopelagic diatoms and increasing abundance of pelagic marine taxa. We conclude that low river discharge, through extension of saline habitat area and longer residence times, likely contributed to the development of the observed marine HABs in the estuary. MHWs and associated declines in discharge are projected to become more common in the Pacific Northwest with climate change, which may alter late summer phytoplankton assemblages in the LCRE.

Characterization and diversity of seed endophytic bacteria of the endemic holoparasitic plant Cistanche armena (Orobanchaceae) from a semi-desert area in Armenia

AbstractWe explored the seed-associated bacterial endophytic microbiome in seeds of the endemic holoparasitic species Cistanche armena from a saline and arid habitat in Armenia. A combination of culture-dependent and molecular techniques was employed for identifying the seed endomicrobiome (culturable and unculturable). From surface-sterilized seeds, 10 phyla, comprising 256 endophytic bacterial genera, were identified. Of the culturable strains, we also investigated the plant growth-promoting (PGP) traits. Most of the isolates were spore forming, halotolerant and alkaliphile Bacillus spp., indicating that the endophytic bacteria of C. armena seeds own traits related to the natural habitat of their host plant. Our results confirm that Bacillus species are common and dominated endophytes from plants growing on saline and arid soils. Pantoea spp. and Stenotrophomonas spp. are more favourable PGP endophytes in seeds of C. armena. The PGP traits of these bacteria, such as production of indole, a precursor of auxin, ACC-deaminase and organic acids have the potential to improve the tolerance of their host plants against the abiotic stresses present in their natural habitat. To the best of our knowledge, this is the first report concerning bacterial seed endophytes of the C. armena.

Seed germination and salinity tolerance of habitat-indifferent halophytes as associated with geographical distribution

Germination response to environmental factors often depends on the seed source. Habitat-indifferent halophytes that can grow well under both saline (SH) and non-saline habitats (NSH) offer a good opportunity to understand salinity tolerance during the germination stage under varying environmental factors, such as temperature and light. This study compared seed germination responses among different populations of two common habitatindifferent halophytes (Salsola drummondii and Suaeda vermiculata) from subtropical hyperarid deserts of the United Arab Emirates (UAE) and semiarid warm sub-tropical areas in Pakistan. This study highlights many similarities and differences in the seed germination and recovery responses of habitat-indifferent halophytes occurring in two contrasting climatic regions. The germination window of UAE seeds was wider, i. e., they germinated at higher rates under all temperatures in both light and darkness. This indicates that seeds of UAE populations can germinate at any time of the year, if conditions are optimal, and faciltate a faster seedling establishment under fluctuating harsh environmental conditions compared to populations from semiarid warm sub-tropical areas in Pakistan. The eco-physiological significance of the responses is also discussed.

Functional differentiation determines the molecular basis of the symbiotic lifestyle of Ca. Nanohaloarchaeota

BackgroundCandidatus Nanohaloarchaeota, an archaeal phylum within the DPANN superphylum, is characterized by limited metabolic capabilities and limited phylogenetic diversity and until recently has been considered to exclusively inhabit hypersaline environments due to an obligate association with Halobacteria. Aside from hypersaline environments, Ca. Nanohaloarchaeota can also have been discovered from deep-subsurface marine sediments.ResultsThree metagenome-assembled genomes (MAGs) representing a new order within the Ca. Nanohaloarchaeota were reconstructed from a stratified salt crust and proposed to represent a novel order, Nucleotidisoterales. Genomic features reveal them to be anaerobes capable of catabolizing nucleotides by coupling nucleotide salvage pathways with lower glycolysis to yield free energy. Comparative genomics demonstrated that these and other Ca. Nanohaloarchaeota inhabiting saline habitats use a “salt-in” strategy to maintain osmotic pressure based on the high proportion of acidic amino acids. In contrast, previously described Ca. Nanohaloarchaeota MAGs from geothermal environments were enriched with basic amino acids to counter heat stress. Evolutionary history reconstruction revealed that functional differentiation of energy conservation strategies drove diversification within Ca. Nanohaloarchaeota, further leading to shifts in the catabolic strategy from nucleotide degradation within deeper lineages to polysaccharide degradation within shallow lineages.ConclusionsThis study provides deeper insight into the ecological functions and evolution of the expanded phylum Ca. Nanohaloarchaeota and further advances our understanding on the functional and genetic associations between potential symbionts and hosts.6R3_PbsEzFSPy16NiyaaD4Video

Natural variation in growth and leaf ion homeostasis in response to salinity stress in Panicum hallii.

Soil salinity can negatively impact plants growth, development and fitness. Natural plant populations restricted to coastal environments may evolve in response to saline habitats and therefore provide insights into the process of salinity adaptation. We investigated the growth and physiological responses of coastal and inland populations of Panicum hallii to experimental salinity treatments. Coastal genotypes demonstrated less growth reduction and superior ion homeostasis compared to the inland genotypes in response to saline conditions, supporting a hypothesis of local adaptation. We identified several QTL associated with the plasticity of belowground biomass, leaf sodium and potassium content, and their ratio which underscores the genetic variation present in this species for salinity responses. Genome-wide transcriptome analysis in leaf and root tissue revealed tissue specific overexpression of genes including several cation transporters in the coastal genotype. These transporters mediate sodium ion compartmentalization and potassium ion retention and thus suggests that maintenance of ionic homeostasis of the coastal genotypes might be due to the regulation of these ion transporters. These findings contribute to our understanding of the genetics and molecular mechanisms of salinity adaptation in natural populations, and widens the scope for genetic manipulation of these candidate genes to design plants more resilient to climate change.

Salinity Tolerance and Ion Accumulation of Coastal and Inland Accessions of Clonal Climbing Plant Species Calystegia sepium in Comparison with a Coastal-Specific Clonal Species Calystegia soldanella

Plant species adapted to saline habitats represent an important resource in the assessment of salinity tolerance mechanisms. The aim of the present study was to analyze salinity tolerance and ion accumulation characteristics for various accessions of Calystegia sepium from different habitats in comparison to these of Calystegia soldanella in controlled conditions. Plants were introduced in culture using stem explants with leaf and were cultivated in controlled conditions under six different substrate salinities. Salinity tolerance of both C. sepium and C. soldanella plants was relatively high, but the tolerance of particular accessions did not depend on the substrate salinity level in their natural habitats. C. sepium accession from a mesophytic non-saline habitat was only slightly negatively affected by increasing substrate salinity. However, coastal accession of C. sepium and coastal-specific species C. soldanella had some similarities in ion accumulation characteristics, both accumulating a high concentration of soluble ions in aboveground parts and excluding them from underground parts. All C. sepium accessions from different habitats represented varied physiotypes, possibly associated with their genetic differences. C. sepium accessions from different habitats can be suggested as models for further studies aiming at dissecting possible genetic, epigenetic and physiological mechanisms of adaptation to heterogeneous environmental conditions.

The colonisation of saline waters is associated with lowered immune responses in aquatic beetles

Abstract The immune response represents a suite of evolved traits that can involve energetic and evolutionary trade‐offs with other energy‐demanding and fitness‐related processes. Here, we tested the hypothesis that aquatic beetles living in inland hypersaline habitats have lower immune capacity than freshwater congeners. Phenoloxidase activity, encapsulation response and antimicrobial peptide activity were compared in freshwater/hypersaline species pairs with differing osmoregulatory capacity and cuticular waterproofing properties in the genera Nebrioporus (Dytiscidae) and Enochrus (Hydrophilidae), independent evolutionary lineages that have colonised saline media separately. Hypersaline species (N. ceresyi and E. jesusarribasi) showed significantly lower phenoloxidase activity and antimicrobial peptide responses than their freshwater relatives (N. clarkii and E. salomonis). Encapsulation responses in freshwater species also appeared to be higher than in hypersaline relatives. Our results reinforce the complex nature of immune responses and suggest that adaptation to saline environments may have involved a trade‐off between osmoregulation and investment in immune defences, but also are consistent with relaxed selection pressures on basal immune responses resulting from lower microbial infection load in saline habitats. In addition, the more resistant cuticle of species occupying such habitats may protect against the entry of parasites, reducing selection pressure on immunity. Because the evolution of salinity tolerance is associated with reduced immune capacity, saline specialists may be particularly vulnerable to the dilution of saline waters and consequent changes in pathogen communities and load following colonisation by more generalist microorganisms.

Spatial genetic structure reveals migration directionality in Mediterranean Ruppia spiralis (Western Sicily)

Mediterranean salinas, originally built for salt production, function as alternative wetlands. A variety of accompanying lagoon, ditch, and marsh systems are suitable habitats for salt-tolerant submerged macrophytes and often characterized by monospecific beds of Ruppia. Traditionally, birds are considered the main dispersal vector of submerged macrophytes. However, Ruppia spiralis habitats are under marine influence and therefore interference of coastal currents in their connectivity might be expected. In this study, we aim to infer connectivity and spatial patterns from population genetic structures. Using nuclear microsatellite loci, the nuclear ribosomal cistron and chloroplast sequences, we investigated the genetic diversity, genetic structure, and demographic history of 10 R. spiralis populations along a 25-km coastal stretch of western Sicily encompassing a variety of saline habitats. We tested for local fine-scaled structures, hypotheses of regional isolation by distance, and migration directionality. Our results revealed a high degree of allele and gene diversity that was locally maintained by outcrossing. At the regional level, we detected isolation by distance and identified three genetically differentiated clusters, with a significant structure that matches an overall north-to-south unidirectional migration model. This directionality follows the main sea current, hence indicating the importance of hydrological connectivity in regional conservation management. Significant fine-scale spatial structures only emerged in some populations and were absent in the ‘salina fridda’ habitat that showed the largest clonal richness. The local site-dependent patterns emphasize a need to examine the influence of disturbances on seed recruitment and clonal growth over small distances.

Synthesizing glycine betaine via choline oxidation pathway as an osmoprotectant strategy in Haloferacales

The accumulation of organic compatible solutes, such as glycine betaine, is one of the osmoprotective strategies used by halophilic archaea to adapt to high salinity. The uptake of glycine betaine from the external environment using various transporters has been widely studied in different halophilic archaea. However, the de novo biosynthesis of glycine betaine and its distribution in halophilic archaea remain unclear. In this study, an extremely halophilic archaea strain, named Halorubrum sp. 2020YC2 and previously isolated from a salt-lake sample, was identified with complete choline oxidation pathway genes. Halorubrum sp. 2020YC2 could synthesize and accumulate 1.56–4.25 μmol per mg of protein of glycine betaine in a defined medium, with its content increasing along with increasing salinity. The intracellular content of glycine betaine remained relatively stable at different salinities when another exogenous solute such as trehalose was provided. The metabolic profile and transcriptional results strongly suggested that the intracellular glycine betaine was derived from serine, which came from the glycolytic intermediate 3-phosphoglycerate when glucose was used as the sole carbon source. Out of 205 available genomes of halophilic archaea, genes encoding the choline oxidation pathway were identified in 30 genomes, and more than half of the strains belonging to order Haloferacales contained the choline oxidation pathway. Phylogenetic analysis further indicated that this pathway evolved from halophilic Proteobacteria, and its absence in some genera indicated a possible gene loss event during evolution. The analysis of reported culture data of halophilic archaea strains eventually demonstrated that the presence of the choline oxidation pathway had no significant effects on the adaptation of Haloferacales to high salinity habitats. Therefore, the de novo biosynthesis of glycine betaine via the choline oxidation pathway could be an auxiliary osmoprotective strategy in halophilic archaea.

Regulatory Control and the Effects of Condensation Water on Water Migration and Reverse Migration of Halostachys caspica (M.Bieb.) C.A.Mey. in Different Saline Habitats

Condensation water has been a recent focus in ecological hydrology research. As one of the main water sources that maintains the food chain in arid regions, condensation water has a significant impact on water balance in arid environments and plays an important role in desert vegetation. This study takes drought desert areas and high-salinity habitats as its focus—selecting Halostachys caspica (M.Bieb.) C.A.Mey. and its community in mild, moderate, and severe salinity soil—analyzed the source of condensation water utilized by these plants, and calculated its percentage of contribution. I. Study results revealed: (1) Scale-like leaves can absorb condensation water and the order of condensation water contribution to plant growth in different salinity habitats are severe > mild > moderate, such that the average contribution rates were 11.13%, 7.10%, and 3.79%, respectively; (2) The migration path of water movement in these three communities are formed in two main ways: (a) rain and condensation water recharge the soil to compensate for groundwater, while some groundwater compensates for river water and partially returns to the atmosphere by soil evaporation and plant transpiration; and (b) rain and condensation water directly compensate for river water and plant roots absorb river water, groundwater, and soil water in order to grow; (3) in mild habitats, the water movement path in plants is as follows: shallow root → stem → branches → leaves and shallow root → deep root; (4) in moderate habitats, stems act as the bifurcation point and the path follows as: stem → branches → leaves and stem → shallow root → deep root; and (5) in severe habitats, the path is as follows: deep root → shallow root → stem → branches → leaves, and finally returning to the atmosphere. These results elucidate the contribution of condensation water on Halostachys caspica growth and the migration path through the Halostachys caspica body. Condensation water obtained by Halostachys caspica communities in different salinity habitats provides a theoretical basis and data supporting the need for future research of condensation water on plants at the physiological level in arid regions and provides reference for the protection of saline soil and its ecological environment in arid regions.

Antarctic Salt-Cones: An Oasis of Microbial Life? The Example of Boulder Clay Glacier (Northern Victoria Land).

The evaporation of a localized, highly saline water body of the Boulder Clay debris-covered glacier, in the Northern Victoria Land, probably generated the accumulation of mirabilite (Na2SO4 × 10H2O) and thenardite (Na2SO4) in a glacier salt-cone. Such an extremely cold and salty environment resembles the conditions on Mars, so it can be considered a terrestrial analog. The study was aimed at gaining a first glimpse at the prokaryotic community associated with Antarctic mirabilite and thenardite minerals and also to find clues about the origin of the salts. For this purpose, samples were analyzed by a next generation approach to investigate the prokaryotic (Bacteria and Archaea) diversity. Phylogenetic analysis allowed the identification of Bacteroidota, Actinobacteriota, Firmicutes, and Gammaproteobacteria as the main bacterial lineages, in addition to Archaea in the phylum Halobacterota. The genera Arthrobacter, Rhodoglobus, Gillisia, Marinobacter and Psychrobacter were particularly abundant. Interestingly, several bacterial and archaeal sequences were related to halotolerant and halophilic genera, previously reported in a variety of marine environments and saline habitats, also in Antarctica. The analyzed salt community also included members that are believed to play a major role in the sulfur cycle.

Comparative study of the effects of different soluble salts on seed germination of wild marigold (Tagetes minuta L.)

Wild marigold (Tagetes minuta L.) is an important aromatic plant species with a high industrial value in its essential oil. It has spread worldwide due to its wide adaptations. However, meager information is available regarding its salt tolerance. Understanding its seed germination behavior is crucial for establishing the plant species in new saline habitats. The present work focuses on the effect of five soluble salts (CaCl2, KCl, MgCl2, Na2SO4 and NaCl) on germination velocity, salinity tolerance index and germination percentage of wild marigold. Five concentrations (0, 50, 100, 150 and 200 mM) of the salts were given in a two-factor factorial, completely randomized design (CRD). The experiment was performed in a programmed culture room at 25 ± 2 ℃ under 16 h of light (PAR: 40 µmol m−2 s−1) and 8 h dark. Findings suggest that seeds of wild marigold exhibit the highest germination percentage (GP) of more than 95% in non-saline (control) conditions. The trend of germination inhibition due to different soluble salts was in the order: Na2SO4 > KCl > NaCl > CaCl2 > MgCl2. There was a significant decrease in germination velocity (0–40.56) and salinity tolerance index (0–96.67) with the elevated levels of salinity (all applied soluble salts). The dose resulting in a 50% decrease in seed germination, i.e., IC50 (inhibition concentration value) of 79.9 mM of solute salts, was obtained for wild marigold. There are strong indications that wild marigold can tolerate moderate salinity levels and can be appraised as a salt-tolerant aromatic crop. The present study's findings will open future horizons of salt tolerance in wild marigold by identifying potential salt tolerant breeding lines.

Oligotrophy vs. copiotrophy in an alkaline and saline habitat of Lonar Lake.

We reported our comparative observations on oligotrophs vs. copiotrophs from a hyper-alkaline and hypersaline habitat, Lonar Lake, situated in the Buldhana district of Maharashtra, India. Cell numbers of oligotrophic and copiotrophic microbes from the sediment were enumerated by the three-tube most probable number (MPN) method using an array of nutrient-rich and oligotrophic (≈10–20 mg carbon L−1) media offering simulated natural conditions of pH and salinity. A total of 50 strains from 15 different genera and 30 different species were isolated from the highest positive dilutions of MPN to identify the taxa of oligotrophs and copiotrophic microorganisms dominating in Lonar Lake. We did not get any true oligotrophs due to their adaptation to higher carbon levels during the isolation procedure. On the contrary, several true copiotrophs, which could not adapt and survive on a low-carbon medium, were isolated. It is also observed that changes in medium composition and nutrient level altered the selection of organisms from the same sample. Our data indicate that copiotrophic microorganisms dominate the eutrophic Lonar Lake, which is also supported by the past metagenomics studies from the same site. We also reported that quick depletion of carbon from oligotrophic medium worked as a limiting factor, inducing cell death after 2–3 generations and preventing the development of visible colonies on plates and sufficient optical density in liquid medium. Therefore, a long-term supply of low levels of carbon, followed by isolation on enriched media, can serve as a good strategy in isolation of novel taxa of microorganism, with industrial or environmental importance.