Acidic Hot Springs Research Articles

Isolation and characterization of a thermophilic sulfur- and iron-reducing thaumarchaeote from a terrestrial acidic hot spring

A deep-branching clade of Thaumarchaeota, conventionally called Terrestrial hot spring creanarchaeotic group (THSCG), is a missing link between thaumarchaeotic ammonia oxidizers and the deeper-branching non-ammonia oxidizers, such as Crenarchaeota and Candidatus Korarchaeota. Here, we report isolation of the first cultivated representative from the THSCG, named as NAS-02. Physiological characterization demonstrated that the isolate was a thermoacidophilic, sulfur- and iron-reducing organoheterotroph, which was supported by gene contents encoded in its complete genome. There was no evidence for ammonia oxidation by the isolate. Members in THSCG are likely thermophiles, and may play roles in degrading cell debris as a scavenger and in biogeochemical cycling of sulfur and iron in the hot environments, as suggested by the physiological characteristics of the isolate and the geographical distribution of the 16S rRNA gene sequences of THSCG in terrestrial hot springs and marine hydrothermal fields. Phylogenetic analysis suggests that the THSCG lineage represented by NAS-02 has gained the ability of sulfur reduction via horizontal gene transfer. Based on the phylogeny and physiology, we propose the name Conexivisphaera calidus gen. nov., sp. nov. to accommodate the isolate.

Subaerial sulfate mineral formation related to acid aerosols at the Zhenzhu Spring, Tengchong, China

AbstractThe Zhenzhu Spring, located in the Tengchong volcanic field, Yunnan, China, is an acid hot spring with high SO42−concentrations and intense acid aerosol generation. In order to understand the formation mechanism of sulfate minerals at the Zhenzhu Spring and provide a better insight into the sulfur isotope geochemistry of the associated Rehai hydrothermal system, we investigated the spring water hydrochemistry, mineralogy and major-element geochemistry of sulfate minerals at the Zhenzhu Spring together with the sulfur-oxygen isotope geochemistry of sulfur-containing materials at the Rehai geothermal field and compared the isotope results with those in other steam-heated environments. Subaerial minerals include a wide variety of sulfate minerals (gypsum, alunogen, pickeringite, tamarugite, magnesiovoltaite and a minor Mg–S–O phase) and amorphous SiO2. The δ34S values of the subaerial sulfate minerals at the Zhenzhu Spring varied subtly from –0.33 to 1.88‰ and were almost consistent with the δ34S values of local H2S (–2.6 to 0.6‰) and dissolved SO42−(–0.2 to 5.8‰), while the δ18O values (–8.94 to 20.1‰) were between that of the spring waters (–10.19 to –6.7‰) and atmospheric O2(~23.88‰). The results suggest that most of the sulfate minerals are derived from the oxidation of H2S, similar to many sulfate minerals from modern steam-heated environments. However, the rapid environmental change (different ratio of atmospheric and water oxygen) at the Zhenzhu Spring accounts for the large variation of δ18O. The formation of subaerial sulfate minerals around the Zhenzhu Spring is related to acid aerosols (vapour and acid water droplets). The intense activity of spring water around vents supply the aerosol with H2SO4(H2S oxidation and acid water droplets formed by bubble bursting) and few cations. Deposition of the acid sulfate aerosol forms the acid condensate, which attacks the underlying rocks and releases many cations and anions to form subaerial sulfate minerals at the Zhenzhu Spring.

Tungsten from typical magmatic hydrothermal systems in China and its environmental transport

Tungsten is of extraordinarily high concentrations in the geothermal waters discharging from several representative Tibetan magmatic hydrothermal systems (up to 1103 μg/L), which are also characterized by exceptionally high W/Mo molar ratios (up to 1182). The geochemical origins of the tungsten in these geothermal waters were investigated, with a comparison to those from Rehai, the sole magmatic hydrothermal system in Yunnan, which is another major part of the Yunnan-Sichuan-Tibet Geothermal Province of China. The results show that the lithology of reservoir host rocks is the primary factor controlling the tungsten concentrations of the geothermal waters, although the contribution of magmatic fluid input cannot be ruled out. In this study, the geothermal waters are generally rich in sulfide, and therefore the molybdenum in the reservoir fluids has been substantially precipitated as the form of molybdenite; in contrast, the reservoir fluids are well undersaturated with respect to tungstenite which is much more soluble than molybdenite. Thus the neutral/alkaline hot springs, i.e. the evolved reservoir fluids, have high W/Mo molar ratios as well. In the hot spring sediments, the distribution pattern of tungsten is quite different. The concentrations of tungsten are the highest in the sediments with high iron concentrations collected from the acid hot spring vents and outflow channels. The adsorption of aqueous tungsten onto iron-bearing minerals, like goethite or pyrite, is favorable at acid pH values and thereby responsible for the very high tungsten concentrations of these acid hot spring sediments. The proportions of thiotungstates in total tungsten are quite low for all the hot springs, as indicated by thermodynamic calculations, suggesting that thiolation of tungstate has little impacts on the environmental transport and fate of geothermal tungsten in the investigated hydrothermal areas. This is the first study to report the tungsten geochemistry of hot springs in mainland China.

Monitoring of the Palladium Concentration in River Water and Sediment at an Acidic Hot Spring Spa Area in Gunma Prefecture.

In an effort to elucidate the deposition pathway of Pd in river sediments, we analyzed the amount of Pd in the river water and sediments of the Yukawa and Yazawa rivers, as well as in the sediments of the Shinaki dam-lake of the Kusatsu hot-spring area, which is located northwest in Gunma Prefecture of Japan. The crystal structures and elemental compositions of the river sediment samples differed significantly before and after neutralization. This was attributed to the lime input, which also affected the Pd abundance ratio obtained by the sequential extraction procedure. Additionally, the low leachability of Pd in the sediment suggested possible difficulties in its recovery. Considering the analysis of the Pd variation in the environments, it was concluded that the Pd content in the sediment of the Shinaki dam-lake was mainly supplied by the Yukawa river water inflowing the surrounding tributary rivers and hot-spring waters before neutralization, rather than the lime input.

Sulfurisphaera javensis sp. nov., a hyperthermophilic and acidophilic archaeon isolated from Indonesian hot spring, and reclassification of Sulfolobus tokodaii Suzuki et al. 2002 as Sulfurisphaera tokodaii comb. nov.

A novel hyperthermophilic, acidophilic and facultatively anaerobic archaeon, strain KD-1T, was isolated from an acidic hot spring in Indonesia and characterized with the phylogenetically related species Sulfurisphaera ohwakuensis Kurosawa et al. 1998, Sulfolobus tokodaii Suzuki et al., 2002 and Sulfolobus yangmingensis Jan et al. 1999. Cells of KD-1T were irregular cocci with diameters of 0.9-1.3 µm. The strain grew at 60-90 °C (optimum 80-85 °C), pH 2.5-6.0 (optimum pH 3.5-4.0) and 0-1.0 % (w/v) NaCl concentration. KD-1T grew anaerobically in the presence of S0 (headspace: H2/CO2) and FeCl3 (headspace: N2). Under aerobic conditions, chemolithoautotrophic growth occurred on S0, pyrite, K2S4O6, Na2S2O3 and H2. This strain utilized various complex substrates, such as yeast extract, but did not grow on sugars and amino acids as the sole carbon source. The main core lipids were calditoglycerocaldarchaeol and caldarchaeol. The DNA G+C content was 30.6 mol%. Analyses of phylogenetic trees based on 16S rRNA and 23S rRNA genes indicated that KD-1T formed an independent lineage near Sulfurisphaera ohwakuensis TA-1T, Sulfolobus tokodaii 7T and Sulfolobus yangmingensis YM1T. On the basis of the results of morphological, physiological, chemotaxonomic and phylogenetic analyses, KD-1T represents a novel species of the genus Sulfurisphaera Kurosawa et al. 1998, for which the name Sulfurisphaera javensis sp. nov. is proposed. The type strain is KD-1T (=JCM 32117T=InaCC Ar81T). Based on the data, we also propose the reclassification of Sulfolobus tokodaii Suzuki et al., 2002 as Sulfurisphaera tokodaii comb. nov. (type strain 7T=JCM 10545T=DSM 16993T).

Description of Alicyclobacillus montanus sp. nov., a mixotrophic bacterium isolated from acidic hot springs.

Three morphologically similar thermo-acidophilic strains, USBA-GBX-501, USBA-GBX-502 and USBA-GBX-503T, were isolated from acidic thermal springs at the National Natural Park Los Nevados (Colombia). All isolates were spore-forming, Gram-stain-positive and motile, growing aerobically at 25-55 °C (optimum ~45 °C) and at pH 1.5-4.5 (optimum pH ~3.0). Phylogenetic analysis of the 16S rRNA gene sequences of these isolates showed an almost identical sequence (99.0 % similarity) and they formed a robust cluster with the closest relative Alicyclobacillus tolerans DSM 16297T with a sequence similarity of 99.0 %. Average similarity to other species of the genus Alicyclobacillus was 93.0 % and average similarity to species of the genus Effusibacillus was 90 %. In addition, the level of DNA-DNA hybridization between strain USBA-GBX-503T and Alicyclobacillus tolerans DSM 16297T was 31.7 %. The genomic DNA G+C content of strain USBA-GBX-503T was 44.6 mol%. The only menaquinone was MK-7 (100.0 %). No ω-alicyclic fatty acids were detected in strain USBA-GBX-503T, and the major cellular fatty acids were C18 : 1ω7c, anteiso-C17 : 0 and iso-C17 : 0. Based on phenotypic and chemotaxonomic characteristics, phylogenetic analysis and DNA-DNA relatedness values, along with low levels of identity at the whole genome level (ANIb and ANIm values of <67.0 and <91.0 %, respectively), it can be concluded that strain USBA-GBX-503T represents a novel species of the genus Alicyclobacillus, for which the name Alicyclobacillus montanus sp. nov. is proposed. The type strain is USBA-GBX-503T (=CMPUJ UGB U503T=CBMAI1927T).

Archaeal Viruses from High-Temperature Environments

Archaeal viruses are some of the most enigmatic viruses known, due to the small number that have been characterized to date. The number of known archaeal viruses lags behind known bacteriophages by over an order of magnitude. Despite this, the high levels of genetic and morphological diversity that archaeal viruses display has attracted researchers for over 45 years. Extreme natural environments, such as acidic hot springs, are almost exclusively populated by Archaea and their viruses, making these attractive environments for the discovery and characterization of new viruses. The archaeal viruses from these environments have provided insights into archaeal biology, gene function, and viral evolution. This review focuses on advances from over four decades of archaeal virology, with a particular focus on archaeal viruses from high temperature environments, the existing challenges in understanding archaeal virus gene function, and approaches being taken to overcome these limitations.

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.

Novel Sulfolobus Virus with an Exceptional Capsid Architecture.

A novel archaeal virus, denoted Sulfolobus ellipsoid virus 1 (SEV1), was isolated from an acidic hot spring in Costa Rica. The morphologically unique virion of SEV1 contains a protein capsid with 16 regularly spaced striations and an 11-nm-thick envelope. The capsid exhibits an unusual architecture in which the viral DNA, probably in the form of a nucleoprotein filament, wraps around the longitudinal axis of the virion in a plane to form a multilayered disk-like structure with a central hole, and 16 of these structures are stacked to generate a spool-like capsid. SEV1 harbors a linear double-stranded DNA genome of ∼23 kb, which encodes 38 predicted open reading frames (ORFs). Among the few ORFs with a putative function is a gene encoding a protein-primed DNA polymerase. Sixfold symmetrical virus-associated pyramids (VAPs) appear on the surface of the SEV1-infected cells, which are ruptured to allow the formation of a hexagonal opening and subsequent release of the progeny virus particles. Notably, the SEV1 virions acquire the lipid membrane in the cytoplasm of the host cell. The lipid composition of the viral envelope correlates with that of the cell membrane. These results suggest the use of a unique mechanism by SEV1 in membrane biogenesis.IMPORTANCE Investigation of archaeal viruses has greatly expanded our knowledge of the virosphere and its role in the evolution of life. Here we show that Sulfolobus ellipsoid virus 1 (SEV1), an archaeal virus isolated from a hot spring in Costa Rica, exhibits a novel viral shape and an unusual capsid architecture. The SEV1 DNA wraps multiple times in a plane around the longitudinal axis of the virion to form a disk-like structure, and 16 of these structures are stacked to generate a spool-like capsid. The virus acquires its envelope intracellularly and exits the host cell by creating a hexagonal hole on the host cell surface. These results shed significant light on the diversity of viral morphogenesis.

Fundamental Study of Behaviors of Rare Metals, Arsenic and Lead with Neutralization of Acid Hot Spring by Using Crushed Mafic Rocks

Fundamental Study of Behaviors of Rare Metals, Arsenic and Lead with Neutralization of Acid Hot Spring by Using Crushed Mafic Rocks

Reduction of structural Fe(III) in nontronite by thermophilic microbial consortia enriched from hot springs in Tengchong, Yunnan Province, China

Iron redox cycling provides one of the most important energy sources supporting microorganisms in terrestrial hot springs. In order to understand microbial Fe(III) reduction processes in hot springs, Fe(III)-reducing bacterial consortia were successfully retrieved from seven acidic hot springs in Tengchong County, Yunnan Province, China (a temperature range from 40.6°C to 74.7°C and a pH range from 2.64 to 4.72). These Fe(III)-reducing consortia were mainly composed of sulfate reducing bacteria (SRB, including Desulfotomaculum, Thermodesulfobacterium and Desulfomicrobium) and organic matter fermenting bacteria (Thermoanaerobacterium and Thermoanaerobacter), with each consortia having specific composition depending on the physio-chemical conditions of the studied hot springs. The obtained consortia were capable of dissimilatory reduction of Fe(III) in nontronite NAu-2 (ferruginous smectite) with 20.8% to 29.8% reduction extent and initial reduction rate of 0.011–0.023mMFe(III)/gNAu-2/h. These extents and rates were comparable to those by mesophilic Fe-reducers in the presence of electron shuttles. Both high temperature and the possible presence of electron-shuttles in hot springs may have accounted for these observed high reduction extents and rates. Various secondary minerals formed during NAu-2 bioreduction, including Fe sulfides and oxides, silicates, and silica. In one spring, illitization and kaolinization of smectite were observed, suggesting that Fe-reducers play important roles in mineral transformation in geothermal environments.

Microbial mat ecosystems: Structure types, functional diversity, and biotechnological application

Microbial mats are horizontally stratified microbial communities, exhibiting a structure defined by physiochemical gradients, which models microbial diversity, physiological activities, and their dynamics as a whole system. These ecosystems are commonly associated with aquatic habitats, including hot springs, hypersaline ponds, and intertidal coastal zones and oligotrophic environments, all of them harbour phototrophic mats and other environments such as acidic hot springs or acid mine drainage harbour non-photosynthetic mats. This review analyses the complex structure, diversity, and interactions between the microorganisms that form the framework of different types of microbial mats located around the globe. Furthermore, the many tools that allow studying microbial mats in depth and their potential biotechnological applications are discussed.

Isolation and Characterization of Metallosphaera Turreted Icosahedral Virus, a Founding Member of a New Family of Archaeal Viruses.

Our understanding of archaeal virus diversity and structure is just beginning to emerge. Here we describe a new archaeal virus, tentatively named Metallosphaera turreted icosahedral virus (MTIV), that was isolated from an acidic hot spring in Yellowstone National Park, USA. Two strains of the virus were identified and were found to replicate in an archaeal host species closely related to Metallosphaera yellowstonensis Each strain encodes a 9.8- to 9.9-kb linear double-stranded DNA (dsDNA) genome with large inverted terminal repeats. Each genome encodes 21 open reading frames (ORFs). The ORFs display high homology between the strains, but they are quite distinct from other known viral genes. The 70-nm-diameter virion is built on a T=28 icosahedral lattice. Both single particle cryo-electron microscopy and cryotomography reconstructions reveal an unusual structure that has 42 turret-like projections: 12 pentameric turrets positioned on the icosahedral 5-fold axes and 30 turrets with apparent hexameric symmetry positioned on the icosahedral 2-fold axes. Both the virion structural properties and the genome content support MTIV as the founding member of a new family of archaeal viruses.IMPORTANCE Many archaeal viruses are quite different from viruses infecting bacteria and eukaryotes. Initial characterization of MTIV reveals a virus distinct from other known bacterial, eukaryotic, and archaeal viruses; this finding suggests that viruses infecting Archaea are still an understudied group. As the first known virus infecting a Metallosphaera sp., MTIV provides a new system for exploring archaeal virology by examining host-virus interactions and the unique features of MTIV structure-function relationships. These studies will likely expand our understanding of virus ecology and evolution.

MUDPOTS AT STEFANOS HYDROTHERMAL CRATER OF NISYROS VOLCANO. AN INSIGHT AT THE HYDROTHERMAL PROCESSES OF AN ACTIVE VOLCANO

On Nisyros island as a result of the volcanic activity and active tectonic, a hydrothermal system develops and it is expressed by 5 types of surface manifestations: i) thermal springs, ii) fumaroles iii) hydrothermal craters, iv) hot grounds and v) mudpots. In general, a mudpot could be described as an acidic hot spring and fumarole with limited water which it is formed in high temperature geothermal areas. Water sample and depositions of mudpots collected, analyzed and studied from Stefanos hydrothermal crater, which is the only site on Nisyros Island, where mudpots occur. Mudpots water is very acidic (pH=2.4), with high sulfate concentration (1375mg/L), due to the H2S(gas) and temperature near the boiling point. As a result, elemental sulfur is found inside the depositions alongside with products of the hydrothermal alteration of the surrounding rocks. In the water and in the depositions were found high concentrations in several elements (e.g. in water: 55mg/L Fe; 19.5mg/L Zn, in depositions: 430mg/Kg Pb; 72mg/Kg Cu; 60mg/Kg Cr) reflecting the alterations processes which are taking place.

Meiofaunal Richness in Highly Acidic Hot Springs in Unzen-Amakusa National Park, Japan, Including the First Rediscovery Attempt for Mesotardigrada.

Extreme environments sometimes support surprisingly high meiofaunal diversity. We sampled runoff from the acidic hot springs of Unzen, Japan. This is the type locality of Thermozodium esakii Rahm, 1937, the only tardigrade in the class Mesotardigrada, which remains contentious in the absence of corroboration or supporting specimens. Our sampling revealed at least three species of arthropods, four rotifers, and five nematodes living in the hot (ca. 40°C) and acidic (ca. pH 2.5) water, but no tardigrades.

Biomediated Precipitation of Calcium Carbonate in a Slightly Acidic Hot Spring, Yunnan Province

A slightly acidic hot spring named Female Tower (t=73.5 degrees C, pH=6.64) is located in the Jifei Geothermal Field, Yunnan Province, southwestern China. The precipitates in the hot spring are composed of large amounts of calcite, aragonite and sulfur. Scanning electron microscopy (SEM) analyses reveal that the microbial mats were formed from various coccoid or rod-shaped filamentous microbes. Transmission electron microscopy (TEM) shows that the intracellular sulfur granules are commonly associated with these microbes. A culture-independent molecular phylogenetic analysis demonstrates that the majority of the bacteria in the spring are sulfur-oxidizing bacteria. In the spring water, H2S concentration is up to 60 ppm, while SO(4)(2-)concentration is only about 10 ppm. We speculate that H2S might derive from sulfur-oxidizing bacteria in this hot spring water, leading to the intracellular formation of sulfur granules. Meanwhile, this reaction increased the pH in the micron-scale microdomains, which fosters the precipitation of calcium carbonate in the microbial mats. The results of this study indicate that the sulfur-oxidizing bacteria might play an important role in calcium carbonate precipitation in slightly acidic hot spring environments.

Geochemical Genesis of Arsenic in the Geothermal Waters from the Rehai Hydrothermal System, Southwestern China

The geothermal waters from the Rehai magmatic hydrothermal system, located in the Tengchong volcanic region, south-western China, are characterized by diversified hydrochemical types and a wide range of pH values. The neutral hot springs in Rehai generally have much higher arsenic concentrations than the acid hot springs. Further inspection shows that the acid, sulfate-rich springs are essentially locally-perched groundwaters heated by H2S-rich steam separated from deep geothermal fluid. Hence, the dissolution of near-surface rocks at moderate temperatures is the sole source of arsenic in the steam-heated acid springs. In comparison, the arsenic in the neutral hot springs, which represent the deep-circulating geothermal fluids, comes from long-term water-rock interactions at much higher reservoir temperatures. Moreover, the possibility that magmatic fluid is a potential arsenic source for the neutral springs in Rehai cannot be ruled out.

Microbial diversity and autotrophic activity in Kamchatka hot springs.

Microbial communities of Kamchatka Peninsula terrestrial hot springs were studied using molecular, radioisotopic and cultural approaches. Analysis of 16S rRNA gene fragments performed by means of high-throughput sequencing revealed that aerobic autotrophic sulfur-oxidizing bacteria of the genus Sulfurihydrogenibium (phylum Aquificae) dominated in a majority of streamers. Another widely distributed and abundant group was that of anaerobic bacteria of the genus Caldimicrobium (phylum Thermodesulfobacteria). Archaea of the genus Vulcanisaeta were abundant in a high-temperature, slightly acidic hot spring, where they were accompanied by numerous Nanoarchaeota, while the domination of uncultured Thermoplasmataceae A10 was characteristic for moderately thermophilic acidic habitats. The highest rates of inorganic carbon assimilation determined by the in situ incubation of samples in the presence of 14C-labeled bicarbonate were found in oxygen-dependent streamers; in two sediment samples taken from the hottest springs this process, though much weaker, was found to be not dependent on oxygen. The isolation of anaerobic lithoautotrophic prokaryotes from Kamchatka hot springs revealed a wide distribution of the ability for sulfur disproportionation, a new lithoautotrophic process capable to fuel autonomous anaerobic ecosystems.

Cultivation of Acidophilic Algae Galdieria sulphuraria and Pseudochlorella sp. YKT1 in Media Derived from Acidic Hot Springs.

Microalgae possess a high potential for producing pigments, antioxidants, and lipophilic compounds for industrial applications. However, the cultivation of microalgae comes at a high cost. To reduce the cost, changes from a closed bioreactor to open pond system and from a synthetic medium to environmental or wastewater-based medium are being sought. However, the use of open pond systems is currently limited because of contamination by undesirable organisms. To overcome this issue, one strategy is to combine acidophilic algae and acidic drainage in which other organisms are unable to thrive. Here, we tested waters from sulfuric acidic hot springs (Tamagawa, pH 1.15 and Tsukahara, pH 1.14) in Japan for the cultivation of the red alga Galdieria sulphuraria 074G and the green alga Pseudochlorella sp. YKT1. Both of these spring waters are rich in phosphate (0.043 and 0.145 mM, respectively) compared to other environmental freshwater sources. Neither alga grew in the spring water but they grew very well when the waters were supplemented with an inorganic nitrogen source. The algal yields were ∼2.73 g dry weight/L for G. sulphuraria and ∼2.49 g dry weight/L for P. sp. YKT1, which were comparable to those in an autotrophic synthetic medium. P. sp. YKT1 grew in the spring waters supplemented either of NH4+, NO3- or urea, while G. sulphuraria grew only when NH4+ was supplemented. For P. sp. YKT1, the spring water was adjusted to pH 2.0, while for G. sulphuraria, no pH adjustment was required. In both cases, no additional pH-buffering compound was required. The phycocyanin of the thermophilic G. sulphuraria is known to be more thermostable than that from the Spirulina platensis currently used in phycocyanin production for commercial use. The phycocyanin content in G. sulphuraria in the Tsukahara water supplemented with NH4+ was 107.42 ± 1.81 μg/mg dry weight, which is comparable to the level in S. platensis (148.3 μg/mg dry weight). P. sp. YKT1 cells in the Tamagawa water supplemented with a nitrogen source formed a large amount of lipid droplets while maintaining cellular growth. These results indicate the potential of sulfuric hot spring waters for large-scale algal cultivation at a low cost.

Life Cycle Characterization of Sulfolobus Monocaudavirus 1, an Extremophilic Spindle-Shaped Virus with Extracellular Tail Development.

We provide here, for the first time, insights into the initial infection stages of a large spindle-shaped archaeal virus and explore the following life cycle events. Our observations suggest that Sulfolobus monocaudavirus 1 (SMV1) exhibits a high adsorption rate and that virions adsorb to the host cells via three distinct attachment modes: nosecone association, body association, and body/tail association. In the body/tail association mode, the entire virion, including the tail(s), aligns to the host cell surface and the main body is greatly flattened, suggesting a possible fusion entry mechanism. Upon infection, the intracellular replication cycle lasts about 8 h, at which point the virions are released as spindle-shaped tailless particles. Replication of the virus retarded host growth but did not cause lysis of the host cells. Once released from the host and at temperatures resembling that of its natural habitat, SMV1 starts developing one or two tails. This exceptional property of undergoing a major morphological development outside, and independently of, the host cell has been reported only once before for the related Acidianus two-tailed virus. Here, we show that SMV1 can develop tails of more than 900 nm in length, more than quadrupling the total virion length. Very little is known about the initial life cycle stages of viruses infecting hosts of the third domain of life, Archaea This work describes the first example of an archaeal virus employing three distinct association modes. The virus under study, Sulfolobus monocaudavirus 1, is a representative of the large spindle-shaped viruses that are frequently found in acidic hot springs. The results described here will add valuable knowledge about Archaea, the least studied domain in the virology field.