Extreme Hypersaline Research Articles

Physiological responses of euryhaline marine fish to naturally-occurring hypersalinity

Hypersaline habitats are generally defined as those with salinities in excess of 40 ppt. Well-known hypersaline regions (e.g. salt and soda lakes) have a well-earned reputation for being among the most inhospitable habitats in the world, and fish endemic to these areas have been the subject of much research related to extremophile physiology. Yet, marine coastal hypersalinity is both a common occurrence and a growing consideration in many marine coastal ecosystems, in part owing to human influence (e.g. evaporation, river diversion, desalination effluent). Importantly, any increase in salinity will elevate the osmoregulatory challenges experienced by a fish, which must be overcome by increasing the capacity to imbibe and absorb water and excrete ions. While great attention has been given to dynamic osmoregulatory processes with respect to freshwater to seawater transitions, and to the extreme hypersalinity tolerance that is associated with the adoption of an osmo-conforming strategy, relatively little focus has been placed on the physiological implications of moderate hypersalinity exposures (e.g. ≤ 60 ppt). Importantly, these exposures often represent the threshold of osmoregulatory performance owing to energetic constraints on ion excretion and efficiency limitations on water absorption. This review will explore the current state of knowledge with respect to hypersalinity exposure in euryhaline fishes, while placing a particular focus on the physiological constraints, plasticity and downstream implications of long-term exposure to moderate hypersalinity.

Trace fossils of hypersaline environment and its implication in identifying tidal inundation boundary in Great Rann of Kachchh, Western India

Extreme hypersaline environments are known to be challenging ecosystems for the survival of organisms. These extreme environments are characterized by high evaporation, resulting in a drastic reduction in the ichnological and bioturbational diversity. Moreover, such environments are poorly understood on account of limited documentation in rock records. The Great Rann of Kachchh forms an exclusive salt-encrusted geomorphic facet and is India’s most extensive exposure to hypersaline deposits. The area is inundated by tidal ingress from the Arabian Sea during the monsoon, followed by an evaporative period. Moreover, tidal ingress in the Rann of Kachchh and its effect on the ecology ispoorly documented. Ichnological investigations of the hypersaline Great Rann of Kachchh revealed four recurring trace fossils, Arenicolites, Palaeophycus, Polykladichnus, and Skolithos, with annelids, and crustaceans as the most likely producers. Furthermore, the existence of their juvenile forms is indicated by the presence of small and tiny subsurface burrows. Hence, in the present research, we used ichnology to document the limit and mechanism of tidal ingress to demarcate the tidal inundation boundary up to the east of Khadir Island. We propose a hypothesis identifying the tidal inundation limit by larval recruits burrows and present an ichnological model for a hypersaline environment.

Insight into endophytic microbial diversity in two halophytes and plant beneficial attributes of Bacillus swezeyi.

This study utilized high-throughput sequencing to investigate endophytic bacteria diversity in halophytic plants Anabasis truncate (AT) and Anabasis eriopoda (AE) from the Aral Sea region. Following sequence processing, 356 Amplicon Sequence Variants (ASVs) were discovered. The abundance and variety of endophytic bacteria were higher in AT. Bacillota, Pseudomonadota, Actinomycetota, and Bacteroidota constituted the dominant in AE, whereas Pseudomonadota, Actinomycetota, Bacteroidota, and Chloroflexota constituted the dominant in AT. Biomarkers were identified through LEFSe analysis, showing host-specific patterns. PCoA indicated distinct bacterial community structures. Phylogenetic analysis revealed diverse endophytic bacteria, including potential novel taxa. PICRUSt2 predicted diverse functions for endophytic bacteria in halophytes, indicating recruitment of beneficial bacterial taxa to adapt to extreme hypersaline conditions, including plant growth-promoting, biocontrol, and halophilic/tolerant bacteria. Moreover, the evolutionary relationship, metabolic capabilities, and plant beneficial potentials of the Bacillus swezeyi strains, previously isolated from the above two halophytes, were analyzed using comparative genomic and physiological analysis. The B. swezeyi strains displayed versatile environmental adaptability, as shown by their ability to use a wide range of carbon sources and their salt tolerances. B. swezeyi possessed a wide range of enzymatic capabilities, including but not limited to proteases, cellulases, and chitinases. Comparative genomic analysis revealed that despite some variations, they shared genetic similarities and metabolic capabilities among the B. swezeyi strains. B. swezeyi strains also displayed outstanding plant-growth-promoting and antagonistic potentials, offering potential solutions to the global food crisis. This study enhances our understanding of microbial diversity in halophytes on saline-alkali land in the West Aral Sea, shedding light on the halophyte microbiome and its collaboration with hosts in highly hypersaline environments. This study also provides a scientific basis for developing high-quality microbial fertilizers and implementing sustainable agricultural practices.

Different Responses of Bacteria and Archaea to Environmental Variables in Brines of the Mahai Potash Mine, Qinghai-Tibet Plateau.

Salt mines feature both autochthonous and allochthonous microbial communities introduced by industrialization. It is important to generate the information on the diversity of the microbial communities present in the salt mines and how they are shaped by the environment representing ecological diversification. Brine from Mahai potash mine (Qianghai, China), an extreme hypersaline environment, is used to produce potash salts for hundreds of millions of people. However, halophiles preserved in this niche during deposition are still unknown. In this study, using high-throughput 16S rRNA gene amplicon sequencing and estimation of physicochemical variables, we examined brine samples collected from locations with the gradient of industrial activity intensity and discrete hydrochemical compositions in the Mahai potash mine. Our findings revealed a highly diverse bacterial community, mainly composed of Pseudomonadota in the hypersaline brines from the industrial area, whereas in the natural brine collected from the upstream Mahai salt lake, most of the 16S rRNA gene reads were assigned to Bacteroidota. Halobacteria and halophilic methanogens dominated archaeal populations. Furthermore, we discovered that in the Mahai potash mining area, bacterial communities tended to respond to anthropogenic influences. In contrast, archaeal diversity and compositions were primarily shaped by the chemical properties of the hypersaline brines. Conspicuously, distinct methanogenic communities were discovered in sets of samples with varying ionic compositions, indicating their strong sensitivity to the brine hydrochemical alterations. Our findings provide the first taxonomic snapshot of microbial communities from the Mahai potash mine and reveal the different responses of bacteria and archaea to environmental variations in this high-altitude aquatic ecosystem.

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.

Origin, accumulation and fate of dissolved organic matter in an extreme hypersaline shallow lake

Hypersaline endorheic aquatic systems (H-SEAS) are lakes/shallow playas in arid and semiarid regions that undergo extreme oscillations in salinity and severe drought episodes. Although their geochemical uniqueness and microbiome have been deeply studied, very little is known about the availability and quality of dissolved organic matter (DOM) in the water column.. A H-SEAS from the Monegros Desert (Zaragoza, NE Spain) was studied during a hydrological wetting-drying-rewetting cycle. DOM analysis included: (i) a dissolved organic carbon (DOC) mass balance; (ii) spectroscopy (absorbance and fluorescence) and (iii) a molecular characterization with Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The studied system stored a large amount of DOC and under the highest salinity conditions, salt-saturated waters (i.e., brines with salinity > 30%) accumulated a disproportionate quantity of DOC, indicating a significant in-situ net DOM production. Simultaneously, during the hydrological transition from wet to dry, the DOM pool showed strong alterations of it molecular composition. Spectroscopic methods indicated that aromatic and degraded DOM was rapidly replaced by fresher, relatively small, microbial-derived moieties with a large C/N ratio. FT-ICR-MS highlighted the accumulation of small, saturated and oxidized molecules (molecular O/C > 0.5), with a remarkable increase in the relative contribution of highly oxygenated (molecular O/C>0.9) compounds and a decrease of aliphatic and carboxyl-rich alicyclic moleculesThese results indicated that H-SEAS are extremely active in accumulating and processing DOM, with the notable release of organic solutes probably originated from decaying microplankton under large osmotic stress at extremely high salinities.

Bacterial Community Structure and Potential Microbial Coexistence Mechanism Associated with Three Halophytes Adapting to the Extremely Hypersaline Environment.

Halophytes play a crucial ecological role in drought and saline–alkali environments. However, there is limited knowledge about the structure of bacterial communities and the potential microbial coexistence mechanism associated with halophytes. This study investigated the diversity and community structure of endophytic and rhizospheric bacteria associated with three halophytes by applying high-throughput sequencing and geochemistry analyses on the studied soils. We collected 18 plant and 21 soil samples, and sequenced the V3 and V4 hypervariable regions of the 16S rRNA gene using next-generation sequencing (NGS). We also assessed geochemistry of the studied soils. The research suggested that rhizospheric bacterial richness and diversity associated with three halophytes were all significantly higher than for endophytic bacteria. The microbial community analysis indicated that Actinobacteria, Firmicutes, Bacteroidetes and Proteobacteria were the dominating bacterial phyla. Most unassigned operational taxonomic units (OTUs) implied that the microbes associated with halophytes contained abundant potential novel taxa, which are significant microbial resources. The high-abundance OTU phylogenetic tree supported the above views as well. Additionally, network analysis indicated that some conditional rare taxa (CRT) also might be keystone taxa during halophyte microbial community construction. The results of non-metric multidimensional scaling (NMDS) ordination analysis indicated significant dissimilarities in the microbial community among different sample groups. Sixty-two biomarkers were detected from seven different sample groups by linear discriminant analysis effect size (LEFSe) analysis. Microbial functions predicted based on phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt2) demonstrated that the abundances of nitrogen metabolism genes of endophytic bacteria were significantly higher than in rhizobacteria. Environmental factor analysis confirmed that different soil properties have different degrees of influence on the abundance and composition of the microbiota. To better adapt to the extreme hypersaline environment, halophytes could specifically recruit some plant beneficial bacterial taxa, such as nitrogen-fixing bacteria and extremely halophilic or halotolerant bacteria, to help them robustly grow and proliferate. All our preliminary results highlight microbial diversity and community related to halophytes grown on saline–alkali land of arid areas. Simultaneously, this work also advanced our further understanding of the halophyte microbiome associated with plants, and their role in plant adaptation to the extremely hypersaline environment.

Effects of Extreme Salinity Stress on a Temperate Mangrove Ecosystem

Mangrove forests provide essential ecosystem services, but are threatened by habitat loss, effects of climatic change and chemical pollutants. Hypersalinity can also lead to mangrove mortality, although mangroves are adapted to saline habitats. A recent dieback event of >9 ha of temperate mangrove (Avicennia marina) in South Australia allowed to evaluate the generality of anthropogenic impacts on mangrove ecosystems. We carried out multidisciplinary investigations, combining airborne remote sensing with on-ground measurements to detect the extent of the impact. The mangrove forest was differentiated into “healthy,” “stressed,” and “dead” zones using airborne LIDAR, RGB and hyperspectral imagery. Differences in characteristics of trees and soils were tested between these zones. Porewater salinities of >100 were measured in areas where mangrove dieback occurred, and hypersalinity persisted in soils a year after the event, making it one of the most extreme hypersalinity cases known in mangrove. Sediments in the dieback zone were anaerobic and contained higher concentrations of sulfate and chloride. CO2 efflux from sediment as well as carbon stocks in mangrove biomass and soil did not differ between the zones a year after the event. Mangrove photosynthetic traits and physiological characteristics indicated that mangrove health was impacted beyond the immediate dieback zone. Normalized Difference Vegetation Index (NDVI), photosynthetic rate, stomatal conductance and transpiration rate as well as chlorophyll fluorescence were lower in the “stressed” than “healthy” mangrove zone. Leaves from mangrove in the “stressed” zone contained less nitrogen and phosphorous than leaves from the “healthy” zone, but had higher arsenic, sulfur and zinc concentrations. The response to extreme hypersalinity in the temperate semi-arid mangrove was similar to response from the sub-/tropical semi-arid mangrove. Mangrove in semi-arid climates are already at their physiological tolerance limit, which places them more at risk from extreme hypersalinity regardless of latitude. The findings have relevance for understanding the generality of disturbance effects on mangrove, with added significance as semi-arid climate regions could expand with global warming.

Metagenomic Assessment of Prokaryotic Diversity within Hypersaline Tuz Lake, Turkey

Tuz Lake is the second biggest lake with an extreme hypersaline environment (over 32% (w/v) salt) in Turkey. It is reported that the lake was of marine origin, and its formation began with tensional movements during the Late Cretaceous and the Late Eocene. We conducted this research to determine the prokaryotic diversity of Tuz Lake by metagenomics approach, which is 16S rRNA amplicon sequencing of microbial communities in their natural environments. Hence, next-generation sequencing and then bioinformatic analysis was used to investigate the microbial structure of halophilic Bacteria and Archaea in Tuz Lake. Metagenomic analysis of reads revealed that all the archaeal populations in Tuz Lake belonged to the Euryarchaeota and Nanoarchaeaeota phyla. Haloquadratum (34%), Haloparvum (31%), Halonotius (7%), Halorubrum (3%), Halapricum (2%), Halobellus (3%), Natronomonas (1%), Halococcus (1%), and Halobacterium (1%) were found as the dominant archaeal genera. The most abundant and diverse bacterial phyla were Bacteroidetes and Proteobacteria. The remaining bacterial taxa were assigned to Acetothermia, Cyanobacteria, Firmicutes, and Halanaerobiaeota. Salinibacter (3%), uncultured microorganisms (1%), Pseudomonas (<1%), Arhodomonas (<1%), Halorhodospira (<1%), Chromobacterium (<1%) were the most common genera in bacterial diversity. Monthly and seasonal potential interactions among environmental factors and taxa were investigated. It was detected that several environmental factors such as temperature, salinity, and drought might have significant effects on microbial richness.

Salted mullet: Protracted occurrence of Mugil cephalus under extreme hypersaline conditions

The fish faunas of eight estuaries along 130 km of the south coast of Western Australia were sampled seasonally for one year, during which Beaufort Inlet became markedly hypersaline (salinities up to 122 and > 100 for six months). These conditions were caused by a combination of low amounts of saline river flow, the bar of this shallow estuary remaining closed for 27 months and high rates of evaporation. Fish faunas in the nearshore, shallow and offshore, deeper waters of Beaufort Inlet were depauperate compared to nearby estuaries. The number of fish species declined as salinity increased, with the highly euryhaline, estuarine-resident atherinid Atherinosoma elongata being the only species to survive throughout the study. The cosmopolitan flathead mullet Mugil cephalus survived for the next longest period, living in salinities in excess of 100 for at least four months and in a maximum salinity of 122. This is the highest known salinity in which a marine-spawning fish species has been found globally. This finding provides support for the cryptic species complex hypothesis pertaining to M. cephalus and that individuals in south-western Australia may be a seperate species. The survival of these species for a relatively protracted time reflects the fact that they are euryhaline and have a suite of adaptations that allow them to occupy environments from freshwater to extreme hypersaline conditions. The longer occurrence of M. cephalus in the extreme salinities than Acanthopagrus butcheri and Aldrichetta forsteri, is likely also related to their primary diet of detritus, particulate organic matter and diatoms, all of which are abundant in Beaufort Inlet. In contrast, piscivorous and zoobenthivorous fish were depauperate and in low abundances, which may reflect limited food resources during hypersaline conditions, and/or more reduced euryhalinity by these species. Clearly, hypersalinity has a marked effect on the faunas and thus ecosystem functioning of estuaries, and with declines in rainfall and hotter temperatures projected in future climate change scenarios, more estuaries are likely to become increasingly hypersaline.

An evaluation of the core bacterial communities associated with hypersaline environments in the Qaidam Basin, China

Hypersaline lakes and saltern areas are important industrial and biodiversity resources in the Qaidam Basin of China that reside at > 2600m asl. Most hypersaline environments in this area are characterized by saturated salinity (~ 300g/L salinity), nearly neutral pH, intense ultraviolet radiation, and extremely variable temperature fluctuations. The core bacterial communities associated with these stressful environments have nevertheless remained uninvestigated. 16S rRNA gene Illumina sequencing analyses revealed that the bacterial communities were dominated by core lineages including the Proteobacteria (39.4-64.6%) and the Firmicutes (17.0-42.7%). However, the relative abundances of common lineages, and especially the five most abundant taxa of Pseudomonas, Lactococcus, Anoxybacillus, Acinetobacter, and Brevundimonas, were highly variable across communities and closely associated with hypersaline characteristics in the samples. Network analysis revealed the presence of co-occurrence high relative abundance taxa (cluster I) that were highly correlated across all hypersaline samples. Additionally, temperature, total organic carbon, K+, and Mg2+ correlated highest with taxonomic distributions across communities. These results highlight the potential mechanisms that could underlie survival and adaptation to these extreme hypersaline ecosystems.

Enhancement of biodiesel yield from a halophilic green microalga isolated under extreme hypersaline conditions through stepwise salinity adaptation strategy

In the present study, a halophilic microalgal species was isolated from a hypersaline lagoon with salinity average of 45.3‰ and identified as Dunaliella salina KSA-HS022. It was further cultivated at a salinity range of 50–250‰, applied directly to batch cultures or through stepwise increase in a semi-continuous culture. The later showed the highest biomass productivity of 0.191 g L−1 d−1 at 125‰, which represented 45.8% higher than the corresponding batch culture (control). Oxidative markers in the control cultures were significantly higher than those of the adapted culture, confirming reduction of oxidative stress by adaptation. In addition, stepwise adaptation showed the highest lipid productivity of 56.5 mg L−1 d−1 at 150‰ (39.9% higher than the corresponding control), which resulted in the highest fatty acid methyl esters productivity. Moreover, stepwise increase of salinity up to 150‰ enhanced the biodiesel characteristics, offering a new route for enhanced biodiesel production at extraordinary salinity levels.

Climate change, mean sea levels, wetland decline and the survival of the critically endangered Capricorn Yellow Chat

AbstractAn isolated population of ~30 Capricorn Yellow Chats (Epthianura crocea macgregori) (Aves: Meliphagidae) occurs on a grassy marine plain (~4000 ha) with complex fresh to hypersaline wetlands bordering unvegetated salt flats and mangroves, the majority less than 2 m above mean sea level (MSL). While there are several species of sedge on the marine plain, only one, a tall salt‐tolerant sedge, Schoenoplectus subulatus, regularly provides tall cover and nesting habitat on the marine plain. Comparison of vegetation data between 2002 and 2018 at four breeding sites showed a loss of S. subulatus at two of the sites in conjunction with persistent extreme hypersalinity. In contrast, sites where S. subulatus recovered had elevated salinity levels coinciding with a drought in 2005–2008, but subsequently returning to pre‐drought levels. Concomitant with the loss of S. subulatus was a substantial decline in Capricorn Yellow Chat abundance. Possible drivers of persistent hypersalinity were an increase in sea level and consequent greater tidal ingress. The two most severely affected sites were relatively close to tidal influence and low points in the landscape. Evaluation of MSL data showed that habitat decline from 2002 to 2018 occurred over a period in which sea level rose by ~80 mm. While it is recognised that other variables are important, this study indicates that if sea‐level rise continues at the 2011–2017 rate of ~8.3 mm per annum, the Curtis Island marine plain will become unsuitable for Capricorn Yellow Chats in the next 60 years or less. Sixty years is likely to be a conservative estimate given that sea‐level rise rates are projected to increase further, as are the influence of more extreme weather events such as drought and storm surges on persistence of key vegetation. Ramifications for other Capricorn Yellow Chat sites and marine plain‐dependent fauna such as shorebirds also need consideration.

An Ecological Perspective on Dolomite Formation in Great Salt Lake, Utah

Protodolomite was detected in sediments from Great Salt Lake (GSL), Utah, U.S.A. that have no history of elevated temperature or pressure, conditions that are thought to promote dolomitization of sedimentary carbonates. Protodolomite was abundant in a non-oolitic sediment core from the South Arm (SA) of GSL at 26% salinity. Protodolomite was also abundant in a non-oolitic NA sediment hand sample yet was absent in a nearby oolitic sediment hand sample in locations that likely receive allochthonous nutrients. Protodolomite was not detected in benthic photosynthetic mats from the SA. However, the mats comprised aragonite with halite and minimal calcite; benthic photosynthetic mats do not form in the NA. To begin to identify potential controls on the formation of protodolomite in the SA and NA of GSL, the composition and abundance of 16S rRNA gene transcripts, carbon cycling activities, and porewater geochemistry of the sediment cores were characterized. Transcripts affiliated with a dominant halophilic, heterotrophic sulfate-reducing bacterium were detected in the uppermost sections of the SA core and their abundance was positively correlated with rates of acetate oxidation/assimilation and concentrations of sulfide. Differences in the quality of organic matter between the SA and NA cores, as indicated by carbon to nitrogen ratios, indicate fresh deposition of photosynthetic biomass at the SA sediment core site but not in the NA sediment core site. Sediment grains from the SA core exhibit micrometer-sized euhedral protodolomite crystals that were not detected in the NA core. Collectively, these observations suggest that deposition of photosynthetic biomass drives the development of a sharp, anoxic lens of heterotrophic sulfate reduction. Sulfide, in turn, may promote dehydration of Mg2+-water complexes and primary protodolomite nucleation and growth. The scarcity of dolomite in the NA sediment core may result from constraints imposed by a combination of extreme hypersalinity and depositional environment on phototrophs and sulfate reducers, their activities, and the thermodynamics of protodolomite formation.

Spatial-temporal distribution of Aureoumbra lagunensis (“brown tide”) in Baffin Bay, Texas

Once limited to the Laguna Madre of Texas, blooms of the brown tide organism, Aureoumbra lagunensis, have recently been reported elsewhere. Previous studies have focused on the role of extreme hypersalinity and lack of grazing pressure as facilitators of brown tide blooms. However, development of blooms in systems that are not experiencing extreme hypersalinity, and also that are undergoing eutrophication, suggests that our understanding of A. lagunensis bloom dynamics requires additional refinement. The goal of this study was to quantify the spatial-temporal distribution of, and potential controls upon, A. lagunensis in Baffin Bay, Texas. Five sites were sampled monthly over a three-year period, encompassing nearly two years of drought and hypersaline conditions, followed by a high rainfall, lower salinity period. A. lagunensis abundances were higher during drought in May 2013 – March 2015 compared to the higher rainfall period of April 2015 – April 2016. Abundances typically peaked in summer months, though the seasonal pattern was disrupted in 2015 during the shift from high to low salinity conditions. Persistently high abundances of A. lagunensis were observed in the Laguna Salada tributary of Baffin Bay, which typically has higher dissolved organic nitrogen concentrations and may be less well flushed than other parts of Baffin Bay. Thus this location may serve as a reservoir for A. lagunensis in the system. Overall, A. lagunensis abundance was positively correlated with DOC and salinity, and negatively correlated with ammonium, orthophosphate, and ciliate biovolume. These results suggest a variety of physical, chemical and biological factors affect A. lagunensis population dynamics and stress the need for more research on nutrient-A. lagunensis relationships.

Characterization of protistan plankton diversity in ancient salt evaporation ponds located in a volcanic crater on the island Sal, Cape Verde.

Salinity is an important factor when exploring the limits known for life. Therefore, hypersaline systems have attracted much attention in recent years. In this study, we investigated the protistan diversity and community composition in two natural salt evaporation ponds (27-30% salinity) located in an ancient volcanic crater on the Cape Verde island Sal using high-throughput DNA sequencing. Our study revealed a broad range of protistan taxa and a high taxonomic diversity within the Ciliophora, Dinophyceae, and Chlorophyta. We detected a total of 23 Dinophyceae families, although Dinophyceae were generally considered to be only this diverse in aquatic environments of less than 10% salinity. Moreover, we uncovered a high degree of genetic novelty in this habitat. The mean similarity of all detected OTUs to previously described sequences was only 93.6%. These findings strongly dispute the traditional view that extreme hypersaline environments generally maintain low protistan diversity. A meta-analysis covering our and previously published data from other inland and coastal salt ponds clearly showed that our samples clustered according to salinity and not biogeography. This result further supports the claim that salinity is a major transition boundary for protistan communities, regardless of their biogeographic origin.

Antimicrobial Activity of Bacillus Persicus 24-DSM Isolated from Dead Sea Mud.

Intorduction:Dead Sea is a hypersaline lake with 34% salinity, gains its name due to the absence of any living macroscopic creatures. Despite the extreme hypersaline environment, it is a unique ecosystem for various halophilic microorganisms adapted to this environment.Aims & Objectives:Halophilic microorganisms are known for various potential biotechnological applications, the purpose of the current research is isolation and screening of halophilic bacteria from Dead Sea mud for potential antimicrobial applications.Methods & Materials:Screening for antagonistic bacteria was conducted by bacterial isolation from Dead Sea mud samples and agar plate antagonistic assay. The potential antagonistic isolates were subjected to biochemical characterization and identification by 16S-rRNA sequencing. Among the collected isolates, four isolates showed potential antagonistic activity against Bacillus subtilis 6633 and Escherichia coli 8739. The most active isolate (24-DSM) was subjected for antagonistic activity and minimal inhibitory concentration against different gram positive and negative bacterial strains after cultivation in different salt concentration media. Results: The results of 16S-rRNA analysis revealed that 24-DSM is very closely related to Bacillus persicus strain B48, which was isolated from hypersaline lake in Iran.Conclusion: Therefore, the isolate 24-DSM is assigned as a new strain of B. persicusi isolated from the Dead Sea mud. B. persicusi 24-DSM showed higher antimicrobial activity, when it was cultivated with saline medium, against all tested bacterial strains, where the most sensitive bacterial strain was Corynebacterium diphtheria 51696.

Changes of fish trophic guilds in Araruama Lagoon, Brazil: What can be inferred about functioning and structure of hypersaline lagoons?

In this paper, the diet and trophic structure of fish assemblages caught in two zones of the largest (∼220 km2) hypersaline coastal lagoon in South America were addressed quarterly along 2011, and the patterns were compared among seasons and to a previous study performed during typical hypersaline conditions (i.e. 1993) to assess the short- and long-term effects of desalinisation. Our results confirmed that in 2011, Araruama Lagoon experienced a strong decrease in salinity, particularly in the autumn, with the ranging values (i.e. 37–48) remaining below to the salinities (i.e. 52–67) reported for most of the 1965–2005 period, but matching those (i.e. ≤ 41 on the average) recorded during the atypical less-hypersaline conditions of 1989–1990. Fish trophic structure recorded during 2011 was composed of five guilds, in decreasing order of biomass: planktivores (31.14%), detritivores (26.24%), invertivores (25.65%), piscivores (15.09%), and omnivores (1.58%). This structure resembled more those of similar, but comparatively less hypersaline systems in Africa and Australia, than that of extreme hypersaline lagoons in Mexico or Araruama lagoon in a typically hypersaline year. Our findings indicate that increased contributions of planktivores and detritivores could be used as promising predictors of, respectively, salination and desalinisation processes and thus shifts in the ecosystem trophic state. Variations on the biomasses of piscivores and invertivores were apparently more related to short-term salinity changes among seasons and across the lagoon zones. Since the relationships between fish trophic structure and desalinisation and its associated effects were complex, long-term studies using complementary and integrative approaches, such as stable isotopes and functional traits, are recommended to confirm our findings for Araruama Lagoon and validate our hypothesis for other similar hypersaline ecosystems.

Isolation and Characterisation of a Halotolerant ω‐Transaminase from a Triassic Period Salt Mine and Its Application to Biocatalysis

AbstractChiral amines are valuable intermediates for the pharmaceutical industry, with up to 40% of current pharmaceuticals containing an amine functionality. However, their syntheses by conventional chemical methods often suffer from a number of key drawbacks. Transaminases (TAms) are pyridoxal phosphate (PLP) dependent enzymes capable of transferring an amine group to a prochiral ketone, offering a green and economically viable alternative to chiral amine production. Despite some high profile successes, TAms suffer from limited substrate scope and the ability to function under challenging conditions often required in reaction processes. Mining of untapped, extremophilic environments represents a viable approach in the search for novel enzymes. We report the cloning and expression of an (S)‐selective ω‐TAm from a Halomonas sp. (Ad2‐TAm), isolated from an extreme hypersaline environment formed during the Triassic period (circa 220 mya). Ad2‐TAm exhibits an ability to convert a range of structurally diverse aldehyde and ketone substrates, with no decrease in conversion up to 1.5 M (8.8%) NaCl. The enzyme is also tolerant to the presence of organic cosolvents up to 30% and accepts a range of amino donors. These characteristics make Ad2‐TAm a promising candidate for industrial applications, whilst also highlighting the value of extreme environments as a source of novel enzymes for the pharmaceutical industry as a whole.

CO2 sequestration potential of halo-tolerant bacterium Pseudomonas aeruginosa SSL-4 and its application for recovery of fatty alcohols

Abstract Bio-mitigation of CO2 utilizing prokaryotes and simultaneous extraction of valuable bio-molecule is fast gaining interest now-a-days. Present work discusses the thermodynamic assessment of CO2 bio-mitigation capability of Pseudomonas aeruginosa SSL-4 isolated from halo alkalophilic habitat in the absence of light. The maximum specific growth (μMax, h−1) of isolate was found to be 0.425 (±0.0025) and 0.34 (±0.0063) at 3% (w/v) salt concentration and 35 °C, respectively. The isolate was cultivated in the environment having initial CO2 (g) concentration of 17(±0.8) % (v/v) using Fe[II] as an energy source (0, 50 and 100 ppm) for evaluating CO2 fixing ability of microorganisms. The maximum CO2 removal efficiency of 92.37 (±2.46) % (v/v) was obtained at 100 ppm of Fe[II] concentration. The isolate has shown the maximum CO2 fixation rate ( R C O 2 ) of 0.04 (±0.003) and 0.06 (±0.001) g/L/d at 50 and 100 ppm of Fe[II] concentration, respectively. FT-IR and GC–MS analysis of obtained leachate revealed the presence of fatty alcohols (C12–C28) and total product recovery (C12–C18) of 0.371 g per g of biomass. The thermodynamic assessment revealed the actual CO2 utilization efficiency of 41.16%. Thus, the isolated strain from extreme hyper saline environment has shown the potential for research dedicated to carbon capture and utilization.