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Polysulfide is a candidate for the redox pairs for thermocell devices; however, its aqueous solution has never been investigated. Polysulfides are in complex equilibria in an aqueous system, and the open-circuit potential of the solution is made of their mixed potential; thus, the dominant redox equilibrium determines its thermoelectric property. In this paper, an aqueous polysulfide thermocell was fabricated, and the underlying mechanism of the polysulfide thermocell was investigated by electrochemical studies, UV-vis spectroscopy at various temperatures, and thermodynamic calculations.A thermocell consisting of redox-active polysulfide in an aqueous NaCl solution was investigated. Spectroelectrochemical measurements reveal the existence of various polysulfide species and polysulfur radical anions. The Seebeck coefficient was associated with the mixing potential of the various redox equilibrium between these polysulfur species. This system could be a low-cost candidate for an aqueous thermocell.

Electroautotrophic microorganisms have attracted great attention since they exhibit a new type of primary production. Here, in situ electrochemical cultivation was conducted using the naturally occurring electromotive forces at a deep-sea hydrothermal vent. The voltage and current generation originating from the resulting microbial activity was observed for 12 days of deployment, with fluctuation in response to tidal cycles. A novel bacterium belonging to the genus Thiomicrorhabdusdominated the microbial community specifically enriched on the cathode. Metagenomic analysis provided the draft genome of the bacterium and the gene repertoire indicated that the bacterium has the potential for thio-autotrophic growth, which is a typical physiological feature of the members of the genus, while the bacterium had a unique gene cluster encoding multi-heme cytochrome cproteins responsible for extracellular electron transfer. Herein, we propose this bacterium as a new species, specifically enriched during electricity generation, as ‘CandidatusThiomicrorhabdus electrophagus’. This finding suggests the natural occurrence of electrosynthetic microbial populations using the geoelectricity in deep-sea hydrothermal environments.

In microbiology, cultivation is a central approach for uncovering novel physiology, ecology, and evolution of microorganisms, but conventional methods have left many microorganisms found in nature uncultured. To overcome the limitations of traditional methods and culture indigenous microorganisms, we applied a two-stage approach: enrichment/activation of indigenous organisms by using a continuous-flow down-flow hanging sponge bioreactor and subsequent selective batch cultivation. Here, we provide a protocol for this bioreactor-mediated technique using activation of deep marine sediment microorganisms and downstream isolation of a syntrophic co-culture containing an archaeon closely related to the eukaryote ancestor (CandidatusPromethearchaeum syntrophicum strain MK-D1) as an example. Both stages can easily be tailored to target other environments and organisms by modifying the inoculum, feed solution/gases, attachment material and/or cultivation media. We anaerobically incubate polyurethane sponges inoculated with deep-sea methane seep sediment in a reactor at 10 °C and feed anaerobic artificial seawater medium and methane. Once phylogenetically diverse and metabolically active microorganisms are adapted to synthetic conditions in the reactor, we transition to growing community samples in glass tubes with the above medium, simple substrates and selective compounds (e.g., antibiotics). To accommodate for the slow growth anticipated for target organisms, primary cultures can be incubated for ≥6–12 months and analyzed for community composition even when no cell turbidity is observed. One casamino acid- and antibiotic-amended culture prepared in this way led to the enrichment of uncultured archaea. Through successive transfer in vitro combined with molecular growth monitoring, we successfully obtained the target archaeon with its partner methanogen as a pure syntrophic co-culture.

The scaly-foot snail (Chrysomallon squamiferum) inhabiting deep-sea hydrothermal vents in the Indian Ocean relies on its sulphur-oxidising gammaproteobacterial endosymbionts for nutrition and energy. In this study, we investigate the specificity, transmission mode, and stability of multiple scaly-foot snail populations dwelling in five vent fields with considerably disparate geological, physical and chemical environmental conditions. Results of population genomics analyses reveal an incongruent phylogeny between the endosymbiont and mitochondrial genomes of the scaly-foot snails in the five vent fields sampled, indicating that the hosts obtain endosymbionts via horizontal transmission in each generation. However, the genetic homogeneity of many symbiont populations implies that vertical transmission cannot be ruled out either. Fluorescence in situ hybridisation of ovarian tissue yields symbiont signals around the oocytes, suggesting that vertical transmission co-occurs with horizontal transmission. Results of in situ environmental measurements and gene expression analyses from in situ fixed samples show that the snail host buffers the differences in environmental conditions to provide the endosymbionts with a stable intracellular micro-environment, where the symbionts serve key metabolic functions and benefit from the host’s cushion. The mixed transmission mode, symbiont specificity at the species level, and stable intracellular environment provided by the host support the evolutionary, ecological, and physiological success of scaly-foot snail holobionts in different vents with unique environmental parameters.

Electroautotrophic microorganisms have attracted great attention since they exhibit a new type of primary production. Here, in situ electrochemical cultivation was conducted using the naturally occurring electromotive forces at a deep-sea hydrothermal vent. The voltage and current generation originating from the resulting microbial activity was observed for 12 days of deployment, with fluctuation in response to tidal cycles. A novel bacterium belonging to the genus Thiomicrorhabdusdominated the microbial community specifically enriched on the cathode. Metagenomic analysis provided the draft genome of the bacterium and the gene repertoire indicated that the bacterium has the potential for thio-autotrophic growth, which is a typical physiological feature of the members of the genus, while the bacterium had a unique gene cluster encoding multi-heme cytochrome cproteins responsible for extracellular electron transfer. Herein, we propose this bacterium as a new species, specifically enriched during electricity generation, as ‘CandidatusThiomicrorhabdus electrophagus’. This finding suggests the natural occurrence of electrosynthetic microbial populations using the geoelectricity in deep-sea hydrothermal environments.

ABSTRACTNDP-forming type acyl-CoA synthetase superfamily proteins are known to have six essential subdomains (1, 2, 3, a, b, c) of which partition and order are varied, suggesting yet-to-be-defined subdomain rearrangement happened in its evolution. Comparison in physicochemical and biochemical characteristics between the recombinant proteins which we made from fragmented subdomains and wild-type protein, acetate-CoA ligase in a hyperthermophilic archaeon, consisting of two distinct subunits (α1-2-3 and βa-b-c) provided a clue to the mystery of its molecular evolutionary passage. Although solubility and thermostability of each fragmented subdomain turned out to be lower than that of wild-type, mixture of the three synthetic subunits of α1-2, α3, and βa-b-c had quaternary structure, thermostability, and enzymatic activity comparable to those of the wild-type. This suggests that substantial independence and mobility of subdomain 3 have enabled rearrangement of the subdomains; and thermostability of the subdomains has constrained the composition of the subunits.

Some deep-sea chemosynthetic invertebrates and their symbiotic bacteria can use molecular hydrogen (H2) as their energy source. However, how much the chemosynthetic holobiont (endosymbiont-host association) physiologically depends on H2oxidation has not yet been determined. Here, we demonstrate that the Campylobacterotaendosymbionts of the gastropod Alviniconcha marisindicain the Kairei and Edmond fields (kAlv and eAlv populations, respectively) of the Indian Ocean, utilize H2in response to their physical and environmental H2conditions, although the 16S rRNA gene sequence of both the endosymbionts shared 99.6% identity. A thermodynamic calculation using in situ H2and hydrogen sulfide (H2S) concentrations indicated that chemosynthetic symbiosis could be supported by metabolic energy via H2oxidation, particularly for the kAlv holobiont. Metabolic activity measurements showed that both the living individuals and the gill tissues consumed H2and H2S at similar levels. Moreover, a combination of fluorescence in situ hybridization, quantitative transcript analyses, and enzymatic activity measurements showed that the kAlv endosymbiont expressed the genes and enzymes for both H2- and sulfur-oxidations. These results suggest that both H2and H2S could serve as the primary energy sources for the kAlv holobiont. The eAlv holobiont had the ability to utilize H2, but the gene expression and enzyme activity for hydrogenases were much lower than for sulfur-oxidation enzymes. These results suggest that the energy acquisitions of A. marisindicaholobionts are dependent on H2- and sulfur-oxidation in the H2-enriched Kairei field and that the mechanism of dual metabolism is controlled by the in situ H2concentration.

Hadal trench bottom (>6000 m below sea level) sediments harbor higher microbial cell abundance compared with adjacent abyssal plain sediments. This is supported by the accumulation of sedimentary organic matter (OM), facilitated by trench topography. However, the distribution of benthic microbes in different trench systems has not been well explored yet. Here, we carried out small subunit ribosomal RNA gene tag sequencing for 92 sediment subsamples of seven abyssal and seven hadal sediment cores collected from three trench regions in the northwest Pacific Ocean: the Japan, Izu-Ogasawara, and Mariana Trenches. Tag-sequencing analyses showed specific distribution patterns of several phyla associated with oxygen and nitrate. The community structure was distinct between abyssal and hadal sediments, following geographic locations and factors represented by sediment depth. Co-occurrence network revealed six potential prokaryotic consortia that covaried across regions. Our results further support that the OM cycle is driven by hadal currents and/or rapid burial shapes microbial community structures at trench bottom sites, in addition to vertical deposition from the surface ocean. Our trans-trench analysis highlights intra- and inter-trench distributions of microbial assemblages and geochemistry in surface seafloor sediments, providing novel insights into ultradeep-sea microbial ecology, one of the last frontiers on our planet.

The origin of eukaryotes remains unclear1–4. Current data suggest that eukaryotes may have emerged from an archaeal lineage known as ‘Asgard’ archaea5,6. Despite the eukaryote-like genomic features that are found in these archaea, the evolutionary transition from archaea to eukaryotes remains unclear, owing to the lack of cultured representatives and corresponding physiological insights. Here we report the decade-long isolation of an Asgard archaeon related to Lokiarchaeota from deep marine sediment. The archaeon—‘CandidatusPrometheoarchaeum syntrophicum’ strain MK-D1—is an anaerobic, extremely slow-growing, small coccus (around 550 nm in diameter) that degrades amino acids through syntrophy. Although eukaryote-like intracellular complexes have been proposed for Asgard archaea6, the isolate has no visible organelle-like structure. Instead, Ca. P. syntrophicum is morphologically complex and has unique protrusions that are long and often branching. On the basis of the available data obtained from cultivation and genomics, and reasoned interpretations of the existing literature, we propose a hypothetical model for eukaryogenesis, termed the entangle–engulf–endogenize (also known as E3) model.

Here, Takai et al. researched the function of discoidin domain receptor 1 (DDR1), a member of the subfamily of receptor tyrosine kinases activated by collagens that is overexpressed in breast and other carcinoma cells. Using bioinformatics analysis, breast cancer cell lines, and knockout mice, they demonstrate that DDR1 ablation leads to aggressive breast cancer, and their findings suggest that the absence of DDR1 provides a growth and adhesion advantage that favors the expansion of basal cells, potentiates fibrosis, and enhances necrosis/hypoxia and basal differentiation of transformed cells to increase their aggression and metastatic potential.

Rich animal and microbial communities have been found at deep-sea hydrothermal vents. Although the biogeography of vent macrofauna is well understood, the corresponding knowledge about vent microbial biogeography is lacking. Here, we apply the multilocus sequence analysis (MLSA) to assess the genetic variation of 109 Sulfurimonas strains with ⩾98% 16S rRNA gene sequence similarity, which were isolated from four different geographical regions (Okinawa Trough (OT), Mariana Volcanic Arc and Trough (MVAT), Central Indian Ridge (CIR) and Mid-Atlantic Ridge (MAR)). Sequence typing based on 11 protein-coding genes revealed high genetic variation, including some allele types that are widespread within regions, resulting in 102 nucleotide sequence types (STs). This genetic variation was predominantly due to mutation rather than recombination. Phylogenetic analysis of the 11 concatenated genes showed a clear geographical isolation corresponding to the hydrothermal regions they originated from, suggesting limited dispersal. Genetic differentiation among Sulfurimonas populations was primarily influenced by geographical distance rather than gas composition of vent fluid or habitat, although in situ environmental conditions of each microhabitat could not be examined. Nevertheless, Sulfurimonas may possess a higher dispersal capability compared with deep-sea hydrothermal vent thermophiles. This is the first report on MLSA of deep-sea hydrothermal vent Epsilonproteobacteria, which is indicative of allopatric speciation.

Rich animal and microbial communities have been found at deep-sea hydrothermal vents. Although the biogeography of vent macrofauna is well understood, the corresponding knowledge about vent microbial biogeography is lacking. Here, we apply the multilocus sequence analysis (MLSA) to assess the genetic variation of 109 Sulfurimonasstrains with ?98% 16S rRNA gene sequence similarity, which were isolated from four different geographical regions (Okinawa Trough (OT), Mariana Volcanic Arc and Trough (MVAT), Central Indian Ridge (CIR) and Mid-Atlantic Ridge (MAR)). Sequence typing based on 11 protein-coding genes revealed high genetic variation, including some allele types that are widespread within regions, resulting in 102 nucleotide sequence types (STs). This genetic variation was predominantly due to mutation rather than recombination. Phylogenetic analysis of the 11 concatenated genes showed a clear geographical isolation corresponding to the hydrothermal regions they originated from, suggesting limited dispersal. Genetic differentiation among Sulfurimonaspopulations was primarily influenced by geographical distance rather than gas composition of vent fluid or habitat, although in situenvironmental conditions of each microhabitat could not be examined. Nevertheless, Sulfurimonasmay possess a higher dispersal capability compared with deep-sea hydrothermal vent thermophiles. This is the first report on MLSA of deep-sea hydrothermal vent Epsilonproteobacteria, which is indicative of allopatric speciation.

Subseafloor microbes beneath active hydrothermal vents are thought to live near the upper temperature limit for life on Earth. We drilled and cored the Iheya North hydrothermal field in the Mid-Okinawa Trough, and examined the phylogenetic compositions and the products of metabolic functions of sub-vent microbial communities. We detected microbial cells, metabolic activities and molecular signatures only in the shallow sediments down to 15.8?m below the seafloor at a moderately distant drilling site from the active hydrothermal vents (450?m). At the drilling site, the profiles of methane and sulfate concentrations and the d13C and dD isotopic compositions of methane suggested the laterally flowing hydrothermal fluids and the in situmicrobial anaerobic methane oxidation. In situmeasurements during the drilling constrain the current bottom temperature of the microbially habitable zone to ~45?°C. However, in the past, higher temperatures of 106–198?°C were possible at the depth, as estimated from geochemical thermometry on hydrothermally altered clay minerals. The 16S rRNA gene phylotypes found in the deepest habitable zone are related to those of thermophiles, although sequences typical of known hyperthermophilic microbes were absent from the entire core. Overall our results shed new light on the distribution and composition of the boundary microbial community close to the high-temperature limit for habitability in the subseafloor environment of a hydrothermal field.

Abiotic reduction of nitrate/nitrite to ammonia in ancient ocean environments is essential for prebiotic chemical evolution and the early evolution of cellular metabolisms. Although Fe-bearing minerals have been extensively studied as reductants, the incompatibility of these reactions with the paleo-oceanic chemical conditions would have contributed only to low conversion rates. A recent model of prebiotic synthesis driven by geoelectricity suggests that less-abundant transition metals might have played a role in ammonia synthesis. Herein, we report that the electrochemical reduction of nitrate/nitrite to ammonia is effectively catalyzed by molybdenum sulfide over a wide pH range (pH 3–11). The pH dependence of the onset potential of the denitrification current indicates that this superior activity is due to the ability to induce concerted proton–electron transfer (CPET), contributing to a turnover frequency comparable to those of the extant Mo-dependent nitrate reductases. In a manner similar to biological dissimilatory denitrification, molybdenum sulfide catalyzes nitrite reduction to ammonia through NO and N2O intermediates, as revealed by online differential electrochemical mass spectroscopy. These findings demonstrate that molybdenum sulfide functions as a new family of bioinspired electrochemical denitrification catalysts and suggest that molybdenum, the indispensable element in extant denitrification enzymes, likely played an essential role in prebiotic ammonia synthesis with the continuous supply of geoelectrical current.

The Capitanian stage is characterized by marine anoxia possibly related to the extinction, although the global redox structure of the Capitanian ocean has not been constrained. We newly report a nitrogen isotope (δ15N) record from a paleo‐atoll limestone at the top of a mid‐Panthalassan seamount to constrain the spatial extent and duration of the Capitanian marine anoxia. The δ15N value of limestone after acid treatment is substantially high for ∼5‐Myr up to +28‰, the highest through the Phanerozoic oceans, suggesting that the nitrogen source (nitrate) was substantially enriched in 15N via denitrification within subsurface oxygen‐deficient zones (ODZs; O2< 5 µM). Numerical modeling of nitrogen isotope dynamics in the upwelling system along the seamount suggests that the possible minimum δ15N value of a global deep‐oceanic nitrate reservoir was ca. +9‰ in the Capitanian (∼4‰ higher than at the present). Furthermore, a redox‐dependent nitrogen isotope mass balance model constrained the global redox structure of the Capitanian superocean. Substantially reducing conditions (O2≤ 20 µM) prevailed at intermediate water depths (100–1,000 m), in association with expanded ODZs with anoxic/euxinic cores along continental margins (≥ ∼0.4% of global ocean volume), while the deep‐ocean remained to be more oxidizing (O2≤ 60 µM). The enhanced open‐ocean productivity associated with the low sea‐level and high nutrient flux to the ocean resulted in the global ocean deoxygenation during the cooling stage. Our model is consistent with previous geologic observations and with a possible link between the long‐term (∼5‐Myr) development of marine dysoxia and the extinction. The Capitanian stage is a peculiar stage characterized by several environmental changes including marine anoxia, possibly related to the large extinction. Previous studies reported the evidence for marine anoxia developed at least locally in the Capitanian, although the spatial extent and duration of anoxia in the superocean Panthalassa in the stage have been poorly constrained. Bioavailable nitrogen is essential for life and the nitrogen isotopic composition of sedimentary record is useful to reconstruct the global nitrogen cycle in association with oceanic redox condition in the past. We report a ∼5‐Myr‐long nitrogen isotope record from a shallow‐water limestone in the lost mid‐superocean during the Capitanian. This unique record reveals major changes in global nitrogen cycle in the stage, that is, the appearance of a substantially 15N‐enriched oceanic nitrate reservoir indicating enhanced anaerobic respiration under reducing conditions. Numerical modeling further constrains that the reducing water masses (O2< 20 μM) prevailed at intermediate water depths (100–1,000 m) in the superocean, in association with the expanded oxygen‐deficient zones with anoxic/euxinic cores developed along the continental margins (at least twice as much as in the modern oceans). Our new model is consistent with the scenario that the long‐term subsurface anoxia/euxinia contributed to the shelf extinction. N isotope record from the mid‐Panthalassa suggesting expanded oxygen‐deficient zones in mid‐water depths (>∼0.4% of global ocean volume)Substantially reducing ocean in association with the low sea‐level, high nutrient flux to the ocean, and enhanced open‐ocean productivityA possible link between the long‐term (∼5‐Myr) deep‐water anoxia/euxinia along the continental margins and the shelf extinction N isotope record from the mid‐Panthalassa suggesting expanded oxygen‐deficient zones in mid‐water depths (>∼0.4% of global ocean volume) Substantially reducing ocean in association with the low sea‐level, high nutrient flux to the ocean, and enhanced open‐ocean productivity A possible link between the long‐term (∼5‐Myr) deep‐water anoxia/euxinia along the continental margins and the shelf extinction

Organisms use various forms and orientations of chitin nanofibres to make structures with a wide range of functions, from insect wings to mussel shells. Lophotrochozoan animals such as snails and annelid worms possess an ancient ‘biomineralization toolkit’, enabling them to flexibly and rapidly evolve unique hard parts. The scaly-foot snail is a gastropod endemic to deep-sea hydrothermal vents, unique in producing dermal sclerites used as sites of sulfur detoxification. Once considered to be strictly proteinaceous, recent data pointed to the presence of chitin in these sclerites, but direct evidence is still lacking. Here, we show that β-chitin fibres (approx. 5% of native weight) are indeed the building framework, through a combination of solid-state nuclear magnetic resonance spectroscopy, wide-angle X-ray diffraction, and electron microscopy. The fibres are uniaxially oriented, likely forming a structural basis for column-like channels into which the scaly-foot snail is known to actively secrete sulfur waste—expanding the known function of chitinous hard parts in animals. Our results add to the existing evidence that animals are capable of modifying and co-opting chitin synthesis pathways flexibly and rapidly, in order to serve novel functions during their evolution.

Eight new strains of deep‐sea hyperthermophilic sulfur reducers were isolated from hydrothermal vent fields at 9°50′N East Pacific Rise (EPR) and at the Cleft and CoAxial segments along the Juan de Fuca Ridge (JdFR). 16S rRNA gene sequence analysis showed that each strain belongs to the genus Thermococcus. Restriction fragment length polymorphism patterns of the 16S/23S rRNA intergenic spacer region revealed that these isolates fell into three groups: those from the EPR, those from fluid and rock sources on the JdFR, and those isolated from Paralvinellaspp. polychaete vent worms from the JdFR. The optimum‐temperature specific growth rates and the temperature ranges for growth were significantly higher and broader for those strains isolated from worms relative to those isolated from low‐temperature diffuse hydrothermal fluids. Furthermore, the worm‐derived isolates generally produced a larger array of proteases and amylases based on zymogram analyses. The zymogram patterns also changed with growth temperature suggesting that these organisms alter their lytic protein suites in response to changes in temperature. This study suggests that there is significant phenotypic diversity in Thermococcusthat is not apparent from their highly conserved 16S rRNA nucleotide sequences.

Molecular phylogenetic survey of naturally occurring archaeal diversities in hot water environments was carried out by using the PCR‐mediated small subunit rRNA gene (SSU rDNA) sequencing. Mixed population DNA was directly extracted from the effluent hot water or sediment of a shallow marine hydrothermal vent at Tachibana Bay, or the acidic hot water of hot spring pools at Mt. Unzen, in Nagasaki Prefecture, Japan. Based on the partial rDNA sequences amplified with an Archaea‐specific primer set, the archaeal populations of hot water environments consisted of phylogenetically and physiologically diverse group of microorganisms. The archaeal populations were varied in each sample and subject to its environmental conditions. In addition, the large number of archaeal rDNA sequences recovered from hot water environments revealed the distant relationship not only to the rDNA sequences of the cultivated thermophilic archaea, but also to the sequences of unidentified archaeal rDNA clones found in other hot water environments. The findings extend our view of archaeal diversity in hot water environments and phylogenetic organization of these organisms.

An archaeal phosphoenolpyruvate carboxylase (PEPC) was purified from an acidophilic extreme thermophile, Sulfolobus acidocaldarius. The native enzyme was a homotetramer of 260±20 kDa molecular mass composed of 60±5 kDa subunits. The enzyme appeared to have a temperature optimum of 90°C and a pH optimum of 8.0. The activity of S. acidocaldariusphosphoenolpyruvate carboxylase was inhibited by l‐aspartate and l‐malate, but not enhanced by any metabolites. In comparison to the enzymatic and molecular properties of all other phosphoenolpyruvate carboxylases including another archaeal entity from the hyperthermophilic methanogen Methanothermus sociabilis, the archaeal phosphoenolpyruvate carboxylases were quite different from bacterial and eucaryal counterparts, and their small size and the lack of positively allosteric regulation were likely to be peculiar to the enzyme of the domain Archaea.

Phosphoenolpyruvate carboxylase (PEPC) was purified for the first time from hyperthermophilic archaeon Methanothermus sociabilis, growing autotrophically with an optimum at 88°C. The optimum temperature for enzyme activity was similar to that for growth and was 85°C. The native enzyme was a homotetramer of 240 kDa molecular mass and the subunit displayed an apparent molecular mass of 60 kDa. The archaeal PEPC was insensitive to various metabolites which are known as allosteric effectors for most bacterial and eucaryal counterparts. The enzyme showed extreme thermostability such that there remained 80% of the enzyme activity after incubation for 2 h at 80°C. These results implied that archaeal PEPC was significantly different from bacterial and eucaryal entities.

Some like it hot: Metal‐like electrical conduction and electrocatalytic function of a black smoker chimney point to a possible new form of energy transfer from hot, reductive hydrothermal fluid to cold, oxygenated seawater by electrical current generation in the sulfide chimney wall.

Seafloor cratering is an important process that records the impact history of the Earth, affects projectile survivability, and determines the mass of ejecta from benthic rock that is transported to the atmosphere. We report experimental hypervelocity impacts of chondrite and other projectiles (olivine, stainless‐steel, polycarbonate) on a water‐covered iron target to derive a scaling relationship for benthic cratering. In situ observations of 5‐km/s impacts quantify the deceleration of projectiles in the water column by shock‐induced deformation and fragmentation. The minimum water depths at which multiple craters appeared on the benthic target were two and four times the projectile diameter for chondrite and stainless steel, respectively. Based on the observed deceleration of projectiles in water, the cratering efficiency of a benthic target for a given impact velocity is predicted to follow an exponential decay law in terms of water depth normalized by projectile diameter (H/d), given by πv∝ exp(−(H/d)/κ), when a projectile of original mass collides with the target. Comparing the volume of the largest crater in the experiments and that derived from the scaling relation, mass ratios of the largest projectile fragment to original projectile in the 5‐km/s impact were calculated to be 0.1–0.3 (H/d= 2–6) and 1.0 ± 0.3 (H/d= 5.5) for chondrite and stainless steel, respectively. Using the scaling relationship, the volume of the transient crater on oceanic crust by an asteroid impact is estimated to be smaller than previously predicted by hydrocode simulation when the asteroid fragmentation in the water column controls seafloor cratering. The hypervelocity (measured in km/s) impact of extraterrestrial bodies in the marine environment is more common than that on land because ∼70% of the Earth's surface is covered by oceans. Seafloor cratering is important for recording Earth's impact history, driving environmental, biotic, and climatic perturbations by ejecting crustal materials into the atmosphere (e.g., the K‐T boundary event); impactors can also affect the fate of extraterrestrial organic matter and may have been key components of primitive life on early Earth (the so‐called panspermia hypothesis). Herein, we simulated the oceanic hypervelocity impacts of asteroids in a laboratory to derive a scaling relationship for benthic cratering. Our results suggest that deformation and fragmentation of projectiles occurs during the impact penetration of water at an initial impact velocity of 5 km/s, thereby controlling the water depth conditions that enable benthic cratering. The experimentally derived scaling relationship of benthic cratering permits the estimation of transient crater volume of oceanic crust in a given water depth by a chondrite impact. Oceanic hypervelocity impacts of asteroids were simulated in a laboratory settingDeformation and fragmentation of projectiles within the water column controlled benthic crateringBased on the experimental data, a scaling relation for benthic cratering is provided Oceanic hypervelocity impacts of asteroids were simulated in a laboratory setting Deformation and fragmentation of projectiles within the water column controlled benthic cratering Based on the experimental data, a scaling relation for benthic cratering is provided

Speciation of iron (Fe) precipitated on bacterial stalks was studied by Fe K-edge µ-XRF-XAFS. Micro-XRF analysis of the stalk samples showed that Fe is precipitated around the stalk. All the µ-XANES spectra at several Fe-accumulated parts showed similar spectra. This study indicated that synchrotron µ-XRF-XAFS is a powerful tool for chemical speciation of metals at single-cell level for bacteria bearing metal.

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Adult T-cell leukemia (ATL) is a highly aggressive neoplasm of helper T lymphocytes and is etiologically associated with human T-cell leukemia virus type I (HTLV-I). Although HTLV-I encoded Tax protein is thought to play a central role in the leukemogenesis of ATL, ATL cells frequently could not produce Tax protein by the somatic mutations, deletion and loss of 5′-LTR. Moreover, a long-term latent period (almost 60 years in Japan) precedes the onset of ATL, suggesting that multistep tumorigenesis is involved in development of ATL in addition to role of viral protein. Such transformation process is thought to include alterations of host genome: genetic and epigenetic changes. The epigenetic alteration, such as DNA methylation and histone modification, is commonly observed in various cancer cells. Recently, we reported that the aberrant expression of MEL1S gene, which is hypomethylated in ATL cells, confers resistance against transforming growth factor-beta.