Identifying the genetic mechanism of medium-low temperature fluoride-enriched geothermal groundwater by the self-organizing map and evaluating health risk in the Wugongshan area, southeast China.

Fluoride-enriched groundwater is a serious threat for groundwater supply around the world. The medium-low temperature fluoride-enriched geothermal groundwater resource is widely distributed in the circum-Wugongshan area. And the fluoride concentration of all geothermal samples exceeds the WHO permissible limit of 1.5 mg/L. The Self-Organizing Map method, hydrochemical and isotopic analysis are used to decipher the driving factors and genetic mechanism of fluoride-enriched geothermal groundwater. A total of 19 samples collected from the circum-Wugongshan geothermal belt are divided into four clusters by the self-organizing map. Cluster I, Cluster II, Cluster III, and Cluster IV represent the geothermal groundwater with the different degree of fluoride concentration pollution, the different hydrochemical type, and the physicochemical characteristic. The high F- concentration geothermal groundwater is characterized by HCO3-Na with alkalinity environment. The δD and δ18O values indicate that the geothermal groundwater origins from the atmospheric precipitation with the recharge elevation of 1000-2100 m. The dissolution of fluoride-bearing minerals is the main source of fluoride ions in geothermal water. Moreover, groundwater fluoride enrichment is also facilitated by water-rock interaction, cation exchange and alkaline environment. Additionally, the health risk assessment result reveals that the fluorine-enriched geothermal groundwater in the western part of Wugongshan area poses a more serious threat to human health than that of eastern part. The fluoride health risks of geothermal groundwater for different group show differentiation, 100% for children, 94.74% for adult females, and 68.42% for adult males, respectively. Compared with adult females and adult males, children faced the greatest health risks. The results of this study provide scientific evaluation for the utilization of geothermal groundwater and the protection of human health around the Wugongshan area.

Hydrogeochemical signatures of spring water in geologically diverse terrains: a case study of Southern Western Ghats, India.

Out of 5 million Indian spring water systems, a few were characterised for hydrochemistry and freshwater potential. The present study focuses on analysing the hydrochemistry, discharge, and drinking/irrigation water quality of both cold and thermal spring clusters namely Southern Kerala Springs (SKS) and Dakshina Kannada Springs (DKS) of Southern Western Ghats, India. Currently, eleven springs from SKS and ten from DKS including one thermal spring (TS) with temperature ranges from 34 to 37 °C were considered. The study revealed that cold springs (CS) of SKS are Na-Cl type, while the thermal and cold-water springs in DKS are Na-HCO3 and mixing water type, respectively. Two distinct mechanisms predominantly define the hydro-chemical composition of the springs-SKS are influenced by precipitation, whereas DKS is likely by chemical weathering processes. While comparing the major ions and saturation indices of thermal springs (TS), it is evident that silicate minerals predominantly affect the chemical composition of water. CaCO3- is oversaturated in TS water and tends to precipitate as a scale layer. PCA showed that both geogenic and anthropogenic factors influence water chemistry. WQI categorized the CS in both the clusters are in the "Excellent" rank as compared to TS. Irrigation water quality signifies that the cold springs are only suitable for irrigation. Moreover, it is evident from the discharge that both SKS and DKS were rainfed in nature. Discharge monitoring designated that the CS could augment drinking water supplies in the nearby regions indicating the necessity of conservation and sustainable use considering future freshwater scarcity.

Tectonic and geological setting influence hot spring microbiology.

Hydrothermal systems form at divergent and convergent boundaries of lithospheric plates and within plates due to weakened crust and mantle plumes, playing host to diverse microbial ecosystems. Little is known of how differences in tectonic setting influence the geochemical and microbial compositions of these hydrothermal ecosystems. Here, coordinated geochemical and microbial community analyses were conducted on 87 high-temperature (>65°C) water and sediment samples from hot springs in Yellowstone National Park, Wyoming, USA (n = 41; mantle plume setting), Iceland (n = 41, divergent boundary), and Japan (n = 5; convergent boundary). Region-specific variation in geochemistry and sediment-associated 16S rRNA gene amplicon sequence variant (ASV) composition was observed, with 16S rRNA gene assemblages being nearly completely distinguished by region and pH being the most explanatory parameter within regions. Several low abundance ASVs exhibited cosmopolitan distributions across regions, while most high-abundance ASVs were only identified in specific regions. The presence of some cosmopolitan ASVs across regions argues against dispersal limitation primarily shaping the distribution of taxa among regions. Rather, the results point to local tectonic and geologic characteristics shaping the geochemistry of continental hydrothermal systems that then select for distinct microbial assemblages. These results provide new insights into the co-evolution of hydrothermal systems and their microbial communities.

Different sulfide to arsenic ratios driving arsenic speciation and microbial community interactions in two alkaline hot springs.

Arsenic (As) is ubiquitous in geothermal fluids, which threatens both water supply safety and local ecology. The co-occurrence of sulfur (S) and As increases the complexity of As migration and transformation in hot springs. Microorganisms play important roles in As-S transformation processes. In the present study, two Tibetan alkaline hot springs (designated Gulu [GL] and Daba [DB]) with different total As concentrations (0.88 mg/L and 12.42 mg/L, respectively) and different sulfide/As ratios (3.97 and 0.008, respectively) were selected for investigating interactions between As-S geochemistry and microbial communities along the outflow channels. The results showed that As-S transformation processes were similar, although concentrations and percentages of As and S species differed between the two hot springs. Thioarsenates were detected at the vents of the hot springs (18% and 0.32%, respectively), and were desulfurized to arsenite along the drainage channel. Arsenite was finally oxidized to arsenate (532 µg/L and 12,700 µg/L, respectively). Monothioarsenate, total As, and sulfate were the key factors shaping the changes in microbial communities with geochemical gradients. The relative abundances of sulfur reduction genes (dsrAB) and arsenate reduction genes (arsC) were higher in upstream portions of GL explaining high thiolation. Arsenite oxidation genes (aoxAB) were relatively abundant in downstream parts of GL and at the vent of DB explaining low thiolation. Sulfur oxidation genes (soxABXYZ) were abundant in GL and DB. Putative sulfate-reducing bacteria (SRB), such as Desulfuromusa and Clostridium, might be involved in forming thioarsenates by producing reduced S for chemical reactions with arsenite. Sulfur-oxidizing bacteria (SOB), such as Elioraea, Pseudoxanthomonas and Pseudomonas, and arsenite-oxidizing bacteria (AsOB) such as Thermus, Sulfurihydrogenibium and Hydrogenophaga, may be responsible for the oxidation of As-bound S, thereby desulfurizing thioarsenates, forming arsenite and, by further abiotic or microbial oxidation, arsenate. This study improves our understanding of As and S biogeochemistry in hot springs.

Metagenome-assembled genomes reveal carbohydrate degradation and element metabolism of microorganisms inhabiting Tengchong hot springs, China.

A hot spring is a distinctive aquatic environment that provides an excellent system to investigate microorganisms and their function in elemental cycling processes. Previous studies of terrestrial hot springs have been mostly focused on the microbial community, one special phylum or category, or genes involved in a particular metabolic step, while little is known about the overall functional metabolic profiles of microorganisms inhabiting the terrestrial hot springs. Here, we analyzed the microbial community structure and their functional genes based on metagenomic sequencing of six selected hot springs with different temperature and pH conditions. We sequenced a total of 11 samples from six hot springs and constructed 162 metagenome-assembled genomes (MAGs) with completeness above 70% and contamination lower than 10%. Crenarchaeota, Euryarchaeota and Aquificae were found to be the dominant phyla. Functional annotation revealed that bacteria encode versatile carbohydrate-active enzymes (CAZYmes) for the degradation of complex polysaccharides, while archaea tend to assimilate C1 compounds through carbon fixation. Under nitrogen-deficient conditions, there were correspondingly fewer genes involved in nitrogen metabolism, while abundant and diverse set of genes participating in sulfur metabolism, particularly those associated with sulfide oxidation and thiosulfate disproportionation. In summary, archaea and bacteria residing in the hot springs display distinct carbon metabolism fate, while sharing the common energy preference through sulfur metabolism. Overall, this research contributes to a better comprehension of biogeochemistry of terrestrial hot springs.

Distribution of Acidophilic Microorganisms in Natural and Man-made Acidic Environments.

Acidophilic microorganisms can thrive in both natural and man-made environments. Natural acidic environments comprise hydrothermal sites on land or in the deep sea, cave systems, acid sulfate soils and acidic fens, as well as naturally exposed ore deposits (gossans). Man-made acidic environments are mostly mine sites including mine waste dumps and tailings, acid mine drainage and biomining operations. The biogeochemical cycles of sulfur and iron, rather than those of carbon and nitrogen, assume centre stage in these environments. Ferrous iron and reduced sulfur compounds originating from geothermal activity or mineral weathering provide energy sources for acidophilic, chemolithotrophic iron- and sulfur-oxidizing bacteria and archaea (including species that are autotrophic, heterotrophic or mixotrophic) and, in contrast to most other types of environments, these are often numerically dominant in acidic sites. Anaerobic growth of acidophiles can occur via the reduction of ferric iron, elemental sulfur or sulfate. While the activities of acidophiles can be harmful to the environment, as in the case of acid mine drainage, they can also be used for the extraction and recovery of metals, as in the case of biomining. Considering the important roles of acidophiles in biogeochemical cycles, pollution and biotechnology, there is a strong need to understanding of their physiology, biochemistry and ecology.

The Effect of Spring Water Geochemistry on Copper Proteins in Tengchong Hot Springs, China.

Copper (Cu) is an essential trace metal cofactor for a variety of proteins; however, excess Cu is toxic to most organisms. Cu homeostasis is maintained by a complex machinery of Cu binding proteins that control the uptake, transport, sequestration, and efflux of Cu ions. Despite the importance of Cu binding proteins in electron transfer, substrate oxidation, superoxide dismutation, and denitrification, little information exists about microbial Cu utilization in extreme environments, where the geochemical conditions may affect Cu bioavailability. Using metagenomic data from 9 hot springs in Tengchong, China, which range in temperature from 42°C to 96°C and in pH from 2.3 to 9, the effects of pH, temperature, and spring geochemistry on the distribution of Cu binding domains of proteins and oxidoreductases were studied. Dissolved Cu and Cu binding domains were detected across all temperature and pH gradients. Cu binding domains of cytochrome c oxidase subunits, heavy-metal-associated domains, and nitrous oxide reductase were detected at all sites. DoxB, a quinol oxidase, and other quinol oxidase subunits were the dominant Cu binding oxidoreductase subunits present at low-pH and high-temperature sites, whereas cbb3-type cytochrome c oxidase subunits were dominant at high-pH and high-temperature sites. Additionally, aa3-type cytochrome c oxidase was more prominent than cbb3-type cytochrome c oxidase under circumneutral-pH conditions. This suggests that the type of cytochrome c oxidase pathway and the Cu proteins employed by microbes to carry out important functions such as energy acquisition and efflux of excess Cu are affected by the physicochemical conditions of the springs.IMPORTANCE Copper is present in a variety of proteins and is required to carry out essential functions by all organisms. However, in hot spring environments, copper availability may be limited due to the high temperatures and the wide range in pH. The significance of our research is in relating the physicochemical environment to the distribution of copper proteins across hot spring environments, which provides increased understanding of primary functions and adaptions in these environments.

Young «oil site¼ of the Uzon Caldera as a habitat for unique microbial life.

BACKGROUND: The Uzon Caldera is one of the places on our planet with unique geological, ecological, and microbiological characteristics. Uzon oil is the youngest on Earth. Uzon oil has unique composition, with low proportion of heavy fractions and relatively high content of saturated hydrocarbons. Microbial communities of the «oil site¼ have a diverse composition and live at high temperatures (up to 97 °C), significant oscillations of Eh and pH, and high content of sulfur, sulfides, arsenic, antimony, and mercury in water and rocks. RESULTS: The study analyzed the composition, structure and unique genetics characteristics of the microbial communities of the oil site, analyzed the metabolic pathways in the communities. Metabolic pathways of hydrocarbon degradation by microorganisms have been found. The study found statistically significant relationships between geochemical parameters, taxonomic composition and the completeness of metabolic pathways. It was demonstrated that geochemical parameters determine the structure and metabolic potential of microbial communities. CONCLUSIONS: There were statistically significant relationships between geochemical parameters, taxonomic composition, and the completeness of metabolic pathways. It was demonstrated that geochemical parameters define the structure and metabolic potential of microbial communities. Metabolic pathways of hydrocarbon oxidation was found to prevail in the studied communities, which corroborates the hypothesis on abiogenic synthesis of Uzon hydrothermal petroleum.

The effect of vehicle on skin absorption of Mg2+ and Ca2+ from thermal spring water.

OBJECTIVE: Thermal spring waters (TSW) are commonly used as active ingredients in cosmetics. Their biological activities directly depend on the ionic composition of the spring. However, in order to exhibit beneficial properties, the minerals need to reach viable skin layers. The present study addresses the incorporation of marketed TSW in model cosmetic formulations and the impact of the formulation on skin absorption of magnesium and calcium ions that are known to improve skin barrier function. METHODS: Marketed TSW was introduced into five formulations. Liposomes were prepared using saturated or unsaturated phospholipids mixed with cholesterol by the thin layer evaporation technique. Emulsions water-in-oil (W/O), oil-in-water (O/W) or double: water-in-oil-in-water (W/O/W) were prepared by high-shear mixing. Skin absorption of Mg2+ and Ca2+ from those formulations was studied in vitro using static Franz diffusion cells under infinite dose condition and under occlusion of the apparatus. RESULTS: Mg2+ and Ca2+ penetrate skin samples from TSW. Encapsulating TSW into double emulsion (TSW/O/W) increased skin absorption of both cations of interest and kept the Ca2+ /Mg2+ ratio equal to that of TSW in each skin layer. The dermal absorption of Mg2+ from the double emulsion departs from both single emulsions. Application of liposome suspension improved the skin absorption of Ca2+ while keeping constant that of Mg2+ , leading to unbalanced Ca2+ /Mg2+ ratio inside skin. CONCLUSION: The beneficial effects of TSW are not only due to their action on the skin surface. Their active components, especially Ca2+ and Mg2+ cations, reach viable skin layers in a formulation-dependent manner. The distribution of ions inside skin depends on the type of formulation.

OBJECTIFS: Les eaux thermales sont couramment utilisées comme substances actives dans les formulations cosmétiques. Leurs activités biologiques dépendent directement de leur composition en ions. L'action des ions s'exerce à différents niveaux dans la peau, mais bien souvent dans les couches profondes, au-delà du stratum corneum, qu'ils doivent donc atteindre. L'objectif de cet article est d'étudier l'absorption des ions magnésium et calcium, reconnus pour leur effet bénéfique sur la fonction barrière de la peau, depuis différentes formes galéniques formulées avec une eau thermale. METHODES: Une eau thermale commerciale a été utilisée comme phase aqueuse dans 5 formulations différentes : des liposomes formulés avec des phospholipides saturés et insaturés et du cholestérol ; des émulsions de différents sens, eau thermale/huile (TSW/O) et huile/eau thermale (O/TSW) ; une émulsion multiple eau thermale/huile/eau (TSW/O/W). L'absorption cutanée du calcium et du magnésium a été étudiée depuis ces différentes formulations, en utilisant la méthode des cellules de Franz, en dose infinie, et en fermant les cellules pour prévenir toute évaporation. RESULTATS: Les ions magnésium et calcium pénètrent dans la peau depuis l'eau thermale, utilisée comme contrôle. L'encapsulation de l'eau thermale dans les gouttelettes internes de l'émulsion double (TSW/O/W) permet de promouvoir la pénétration des deux ions d'intérêt dans chaque couche de la peau tout en respectant le rapport Ca2+ /Mg2+ obtenu avec l'eau thermale, contrairement aux émulsions simples. Les liposomes augmentent la pénétration cutanée des ions calcium, tandis que celle des ions magnésium reste constante, ce qui conduit à des rapports Ca2+ /Mg2+ élevés dans la peau. CONCLUSION: Les effets thérapeutiques des eaux thermales ne sont pas seulement dus à une action de surface. Les ions comme le calcium et le magnésium pénètrent dans la peau et exercent une action en profondeur qui dépend de la formulation dans laquelle ils sont formulés. En effet, leur distribution ions dépend de la formulation qui les contient.

Geologic legacy spanning >90 years explains unique Yellowstone hot spring geochemistry and biodiversity.

Little is known about how the geological history of an environment shapes its physical and chemical properties and how these, in turn, influence the assembly of communities. Evening primrose (EP), a moderately acidic hot spring (pH 5.6, 77.4°C) in Yellowstone National Park (YNP), has undergone dramatic physicochemical change linked to seismic activity. Here, we show that this legacy of geologic change led to the development of an unusual sulphur-rich, anoxic chemical environment that supports a unique archaeal-dominated and anaerobic microbial community. Metagenomic sequencing and informatics analyses reveal that >96% of this community is supported by dissimilatory reduction or disproportionation of inorganic sulphur compounds, including a novel, deeply diverging sulphate-reducing thaumarchaeote. When compared to other YNP metagenomes, the inferred functions of EP populations were like those from sulphur-rich acidic springs, suggesting that sulphur may overprint the predominant influence of pH on the composition of hydrothermal communities. Together, these observations indicate that the dynamic geological history of EP underpins its unique geochemistry and biodiversity, emphasizing the need to consider the legacy of geologic change when describing processes that shape the assembly of communities.

Probing the geological source and biological fate of hydrogen in Yellowstone hot springs.

Hydrogen (H2 ) is enriched in hot springs and can support microbial primary production. Using a series of geochemical proxies, a model to describe variable H2 concentrations in Yellowstone National Park (YNP) hot springs is presented. Interaction between water and crustal iron minerals yields H2 that partition into the vapour phase during decompressional boiling of ascending hydrothermal fluids. Variable vapour input leads to differences in H2 concentration among springs. Analysis of 50 metagenomes from a variety of YNP springs reveals that genes encoding oxidative hydrogenases are enriched in communities inhabiting springs sourced with vapour-phase gas. Three springs in the Smokejumper (SJ) area of YNP that are sourced with vapour-phase gas and with the most H2 in YNP were examined to determine the fate of H2 . SJ3 had the most H2 , the most 16S rRNA gene templates and the greatest abundance of culturable hydrogenotrophic and autotrophic cells of the three springs. Metagenomics and transcriptomics of SJ3 reveal a diverse community comprised of abundant populations expressing genes involved in H2 oxidation and carbon dioxide fixation. These observations suggest a link between geologic processes that generate and source H2 to hot springs and the distribution of organisms that use H2 to generate energy.

New archaeal viruses discovered by metagenomic analysis of viral communities in enrichment cultures.

Viruses infecting hyperthermophilic archaea of the phylum Crenarchaeota display enormous morphological and genetic diversity, and are classified into 12 families. Eight of these families include only one or two species, indicating sparse sampling of the crenarchaeal virus diversity. In an attempt to expand the crenarchaeal virome, we explored virus diversity in the acidic, hot spring Umi Jigoku in Beppu, Japan. Environmental samples were used to establish enrichment cultures under conditions favouring virus replication. The host diversity in the enrichment cultures was restricted to members of the order Sulfolobales. Metagenomic sequencing of the viral communities yielded seven complete or near-complete double-stranded DNA virus genomes. Six of these genomes could be attributed to polyhedral and filamentous viruses that were observed by electron microscopy in the enrichment cultures. Two icosahedral viruses represented species in the family Portogloboviridae. Among the filamentous viruses, two were identified as new species in the families Rudiviridae and Lipothrixviridae, whereas two other formed a group seemingly distinct from the known virus genera. No particle morphotype could be unequivocally assigned to the seventh viral genome, which apparently represents a new virus type. Our results suggest that filamentous viruses are globally distributed and are prevalent virus types in extreme geothermal environments.

Ecological Divergence with Gene Flow in a Thermophilic Cyanobacterium.

How ecological diversity is maintained and distributed within populations is a longstanding question in microbial ecology. In the thermophilic cyanobacterium Synechococcus B', high observed levels of recombination are predicted to maintain ecological variation despite the simultaneous action of diverse selective pressures on different regions of the genome. To investigate ecological diversity in these bacteria, we directly isolated laboratory strains of Synechococcus B' from samples collected along the thermal gradients of two geothermal environments in Yellowstone National Park. Extensive recombination was evident for a multi-locus sequence data set, and, consequently, our sample did not exhibit the sequence clustering expected for distinct ecotypes evolving by periodic clonal selection. Evidence for local selective sweeps at specific loci suggests that sweeps may be common but that recombination is effective for maintaining diversity of unlinked genomic regions. Thermal performance for strain growth was positively associated with the temperature of the environment, indicating that Synechococcus B' populations consist of locally adapted ecological specialists that occupy specific thermal niches. Because this ecological differentiation is observed despite the absence of dispersal barriers among sites, we conclude that these bacteria may freely exchange much of the genome but that barriers to gene flow exist for loci under direct temperature selection.

Rhodobacter thermarum sp. nov., a novel phototrophic bacterium isolated from sediment of a hot spring.

An ovoid to rod-shaped, phototrophic, purple non-sulfur bacterium was isolated from a sediment sample of a hot spring in Tibet, China. Cells of strain YIM 73036T were Gram-stain negative, non-motile and multiplied by binary fission. Strain YIM 73036T grew optimally at pH 7.0-7.5 at 37-45 °C. Growth occurred in 0.5-3.5% (w/v) NaCl. Vitamins were not required for growth. The presence of photosynthesis genes pufL and pufM were shown and photosynthesis pigments were formed. Bacteriochlorophyll α, the bacteriopheophytin and carotenoids were present as photosynthetic pigments. Internal cytoplasmic membranes were of the lamellar type. The organism YIM 73036T was able to grow chemo-organoheterophically, chemo-lithoautotrophically and photo-organoheterotrophically but photo-lithoautotrophic and fermentative growth were not demonstrated. Phylogenetic analysis on the basis of 16S rRNA gene sequences showed that strain YIM 73036T is closely related to Rhodobacter blasticus ATCC 33485T (96.65% sequence similarity) and clustered with species of the genus Rhodobacter of the family Rhodobacteraceae. Whole-genome sequence analyses based on the average nucleotide BLAST identity (ANI < 82%) indicated that this isolate belongs to a novel species. The genomic DNA G+C content of organism YIM 73036T was determined to be 66.0 mol%. Strain YIM 73036T contained Q-10 as the predominant ubiquinone and C18:1ω7c, C18:1ω7c 11-methyl and C18:0 as the major fatty acids. The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and unidentified phospholipid. Differential phenotypic and chemotaxonomic properties, together with the phylogenetic distinctiveness, demonstrated that strain YIM 73036T is distinguishable from other species of the genus Rhodobacter. On the basis of the data presented, strain YIM 73036T is considered to represent a novel species of the genus Rhodobacter, for which the name Rhodobacter thermarum sp. nov. [type strain YIM 73036T (= KCTC 52712T = CCTCC AB 2016298T)] is proposed.

Arsenic-tolerant microbial consortia from sediments of Copahue geothermal system with potential applications in bioremediation.

Although arsenic (As) is recognized as a toxic element for living species, some microorganisms have the ability to tolerate and transform it; recent studies have proposed to take advantage of such capacity to develop sustainable bioremediation strategies. In this study, we evaluated the adaptation to increasing concentrations of As(III) and As(V) of three metabolically different microbial cultures (heterotrophic, autotrophic-acidophilic, and anaerobic) obtained from a sample with low-soluble As content from the Copahue geothermal system. At the end of the adaptation process, the heterotrophic culture was able to grow at 20 mM and 450 mM of As(III) and As(V), respectively; the autotrophic-acidophilic culture showed tolerance to 15 mM of As(III) and 150 mM of As(V), whereas the anaerobic culture only developed in As(V) at concentrations up to 50 mM. The most tolerant consortia were characterized by their growth performance, complexity, and the presence of genes related to As metabolism and resistance. Regarding the consortia complexity, the predominant genera identified were: Paenibacillus in both heterotrophic consortia, Acidithiobacillus in the autotrophic-acidophilic consortium tolerant to As(III), Acidiphilium in the autotrophic-acidophilic consortium tolerant to As(V), and Thiomonas and Clostridium in the anaerobic consortium. This study is the first report of As tolerance microorganisms obtained from Copahue and reasserts the versatility and flexibility of the community of this natural extreme environment; also, it opens the door to the study of possible uses of these consortia in the design of biotechnological processes where the As concentration may fluctuate.

Reactive transport of arsenic-enriched geothermal spring water into a sedimentary aquifer.

The movement of high-arsenic (As)-concentration Beitou geothermal spring water up to 4600 µg/L from the upstream area may affect the downstream Guandu plain and Guandu wetland. The major As pathway is via the subsurface flow. The study assesses the fate and transport of As-enriched geothermal spring water in the Beitou-Guandu area. The groundwater head and flow field velocity are first simulated by using HYDROGEOCHEM-fluid flow model. The steady state flow field is well-calibrated with root mean square error 1.73 m and R2 = 0.992. The spatial-temporal distributions of As in the Beitou-Guandu area are simulated by the HYDROGEOCHEM reactive transport model using the calibrated steady state flow field. The results show that high As concentration (250 µg/L) in groundwater of Guandu plain was caused by the movement of high As concentration from the Beitou geothermal spring water. In contrast, the low As concentration (5-50 µg/L) in Guandu wetland was mitigated by the tidal water dilution. The simulated As concentrations increase in the first 3 years, and then gradually decrease due to the adsorption of As on the iron oxide minerals ferrihydrite and iron sulfide minerals pyrite. Furthermore, the hydrogeochemical transport model is applied to assess the effect of bioaccumulation of As by the mangrove plants of Guandu wetland. The dominant mangrove plants, Kandelia obovata, can reduce about 5-30 µg/L As concentration in groundwater. It may be one of sinks of As in Guandu wetland. The inclusion of K. obovata can uptake the aqueous As and allow the simulated As concentration further close to the field measurement in the Guandu wetland. The study successfully models the reactive chemical transport of As by considering both geochemical reactions and biochemical uptakes in the Beitou-Guandu area. The result demonstrates that the complex biogeochemical transport can be quantified by the sophisticated HYDROGEOCHEM model. Moreover, the salient features of the biogeochemical reactions can be recovered and elucidated through a series of systematic simulation.

Microbiological studies of hot springs in India: a review.

The earliest microbiological studies on hot springs in India date from 2003, a much later date compared to global attention in this striking field of study. As of today, 28 out of 400 geothermal springs have been explored following both culturable and non-culturable approaches. The temperatures and pH of the springs are 37-99 °C and 6.8-10, respectively. Several studies have been performed on the description of novel genera and species, characterization of different bio-resources, metagenomics of hot spring microbiome and whole genome analysis of few isolates. 17 strains representing novel species and many thermostable enzymes, including lipase, protease, chitinase, amylase, etc. with potential biotechnological applications have been reported by several authors. Influence of physico-chemical conditions, especially that of temperature, on shaping the hot spring microbiome has been established by metagenomic investigations. Bacteria are the predominant life forms in all the springs with an abundance of phyla Firmicutes, Proteobacteria, Actinobacteria, Thermi, Bacteroidetes, Deinococcus-Thermus and Chloroflexi. In this review, we have discussed the findings on all microbiological studies that have been carried out to date, on the 28 hot springs. Further, the possibilities of extrapolating these studies for practical applications and environmental impact assessment towards protection of natural ecosystem of hot springs have also been discussed.

Marine-influenced microbial communities inhabit terrestrial hot springs on a remote island volcano.

Raoul Island is a subaerial island volcano approximately 1000 km northeast of New Zealand. Its caldera contains a circumneutral closed-basin volcanic lake and several associated pools, as well as intertidal coastal hot springs, all fed by a hydrothermal system sourced from both meteoric water and seawater. Here, we report on the geochemistry, prokaryotic community diversity, and cultivatable abundance of thermophilic microorganisms of four terrestrial features and one coastal feature on Raoul. Hydrothermal fluid contributions to the volcanic lake and pools make them brackish, and consequently support unusual microbial communities dominated by Planctomycetes, Chloroflexi, Alphaproteobacteria, and Thaumarchaeota, as well as up to 3% of the rare sister phylum to Cyanobacteria, Candidatus Melainabacteria. The dominant taxa are mesophilic to moderately thermophilic, phototrophic, and heterotrophic marine groups related to marine Planctomycetaceae. The coastal hot spring/shallow hydrothermal vent community is similar to other shallow systems in the Western Pacific Ocean, potentially due to proximity and similarities of geochemistry. Although rare in community sequence data, thermophilic methanogens, sulfur-reducers, and iron-reducers are present in culture-based assays.

Unexpected fungal communities in the Rehai thermal springs of Tengchong influenced by abiotic factors.

Fungal communities represent an indispensable part of the geothermal spring ecosystem; however, studies on fungal community within hot springs are still scant. Here, we used Illumina HiSeq 2500 sequencing to detect fungal community diversity in extremely acidic hot springs (pH < 4) and neutral and alkaline springs (pH > 6) of Tengchong-indicated by the presence of over 0.75 million valid reads. These sequences were phylogenetically assigned to 5 fungal phyla, 67 order, and 375 genera, indicating unexpected fungal diversity in the hot springs. The genera such as Penicillium, Entyloma, and Cladosporium dominated the fungal community in the acidic geothermal springs, while the groups such as Penicillium, Engyodontium, and Schizophyllum controlled the fungal assemblages in the alkaline hot springs. The alpha-diversity indices and the abundant fungal taxa were significantly correlated with physicochemical factors of the hot springs particularly pH, temperature, and concentrations of Fe2+, NH4+, NO 2-, and S2-, suggesting that the diversity and distribution of fungal assemblages can be influenced by the complex environmental factors of hot springs.

Microbial diversity in acidic thermal pools in the Uzon Caldera, Kamchatka.

Microbial communities of four acidic thermal pools in the Uzon Caldera, Kamchatka, Russia, were studied using amplification and pyrosequencing of 16S rRNA gene fragments. The sites differed in temperature and pH: 1805 (60 °C, pH 3.7), 1810 (90 °C, pH 4.1), 1818 (80 °C, pH 3.5), and 1807 (86 °C, pH 5.6). Archaea of the order Sulfolobales were present among the dominant groups in all four pools. Acidilobales dominated in pool 1818 but were a minor fraction at the higher temperature in pool 1810. Uncultivated Archaea of the Hot Thaumarchaeota-related clade were present in significant quantities in pools 1805 and 1807, but they were not abundant in pools 1810 and 1818, where high temperatures were combined with low pH. Nanoarchaeota were present in all pools, but were more abundant in pools 1810 and 1818. A similar abundance pattern was observed for Halobacteriales. Thermophilic Bacteria were less diverse and were mostly represented by aerobic hydrogen- and sulfur-oxidizers of the phylum Aquificae and sulfur-oxidising Proteobacteria of the genus Acidithiobacillus. Thus we showed that extremely acidic hot pools contain diverse microbial communities comprising different metabolic groups of prokaryotes, including putative lithoautotrophs using energy sources of volcanic origin, and various facultative and obligate heterotrophs.