Iheya Ridge Research Articles

Mn‑carbonate deposition in a seafloor hydrothermal system (CLAM field, Iheya Ridge, Okinawa Trough): Insights from mineralogy, geochemistry and isotope studies

A seafloor hydrothermal system located at the Iheya Ridge (Okinawa Trough), named CLAM, deposits Mn‑carbonate chimneys that have no analogue found so far on the seafloor. The chimneys are composed of Mn-calcite and Ca-rhodochrosite. The crystallographic differences between these carbonates appear to control the rare earth elements (REE) partitioning between them that results in enrichment of the Ca-rhodochrosite in middle and heavy REE, and enrichment of the Mn-calcite in light REE. Chemistry of the CLAM hydrothermal fluids suggests: (1) low water/rock ratio of the hydrothermal system; (2) phase separation and dominance of low-chlorinity vapor phase; (3) sub-seafloor formation of Na-rich alteration minerals during fluid/rock reactions; (4) removal of some elements from the seawater to the host rocks during the seawater/rock interaction; (5) high Mn/Ca ratio of the basement rocks is responsible for the high Mn concentration in the hydrothermal fluids. C-O-isotope compositions of the CLAM Mn‑carbonates suggest they precipitated through binary mixing of end-member hydrothermal fluid and seawater accompanied by progressive degassing and cooling of the fluid. Mn-calcite precipitated from almost pure end-member hydrothermal fluid, whereas Ca-rhodochrosite precipitated from seawater-dominated vent fluid. Mg-isotope fractionation during Mn‑carbonate precipitation is assumed to depend on carbonate growth conditions and resulting carbonate mineralogy. S-isotope composition of the CLAM Mn‑carbonates suggests that the Ca-rhodochrosite precipitated in oxic conditions through rapid mixing of hydrothermal fluid and seawater, whereas the Mn-calcite precipitated in reduced conditions (thermochemical or microbial sulfate reduction) through slow mixing of hydrothermal fluid and seawater. Sr-isotope composition of the CLAM hydrothermal fluids is close to that of Okinawa Trough deep seawater. In contrast, Sr-isotopes in the CLAM Mn‑carbonates are more variable, indicating that Sr was derived from seawater, local lavas and sediments. Nd-isotope composition of the Mn‑carbonates indicates that Nd was derived from the local lavas and sediments. Pb in the majority of the CLAM Mn‑carbonates is of sedimentary origin (Pb isotope data), but involvement of anthropogenic Pb in the hydrothermal system is inferred for some Mn-calcite samples. Stability phase diagram modeling coupled with C-O-S-Sr-isotope data suggest that in the CLAM vent fluid the rhodochrosite is stable in a narrow Eh-pH range (6 < pH < 10; Eh > 0) and in a wide range of [Mn] and [Ca] activities, whereas calcite precipitates from a close to the end-member hydrothermal fluid in reduced conditions (Eh < 0).

Timescales of Magma Mixing Beneath the Iheya Ridge, Okinawa Trough: Implications for the Stability of Sub-Seafloor Magmatic Systems

Submarine volcanic eruptions can be destructive for marine environments and resources. Magma mixing is considered to be an important trigger for volcanic eruptions. Determining the magma residence time from mixing to eruption is conducive to assessing the stability of magmatic systems, especially beneath the seafloor where in situ volcano monitoring is inaccessible. Here, we estimated the timescale of magma mixing beneath the Iheya Ridge, Okinawa Trough, which is characterized by pervasive magma mixing. We focused on andesitic and rhyolitic magma generated by basalt–rhyolite mixing and rhyolite–rhyolite mixing, respectively. By taking advantage of the Mg diffusion chronometry, we showed that the andesitic magma resided in the magma chamber for very short time (~0.1–0.3 years), whereas the residence time of the rhyolitic magma was much longer (~80–120 years). The different times might be in part related to the different rheology of the mixed magmas. The short residence time of the andesitic magma suggested efficient magma mixing that allowed the andesites to be erupted, which may explain the appearance of scarce andesites in basalt–rhyolite dominant settings. However, the rapid mixing and eruption of magma is a disadvantage for the development and preservation of seafloor hydrothermal resources. Therefore, we suggest that the stability of sub-seafloor magma systems must be evaluated during the assessment of seafloor sulfide resources and mining prospects.

Integrated major and trace element study of clinopyroxene in basic, intermediate and acidic volcanic rocks from the middle Okinawa Trough: Insights into petrogenesis and the influence of subduction component

Magmatism is very common in the Okinawa Trough. However, the influence of magmatic processes, including fractional crystallization and magma mixing, on the petrogenesis of volcanic rocks is poorly understood. The in situ major and trace element compositions of clinopyroxene in co-genetic basalts, andesites, trachyandesites and rhyolites from the Iheya Ridge in the middle Okinawa Trough are examined to determine their petrogenesis and the influence of slab subduction. Regarding the types of mineral zoning, in basalt and andesite, clinopyroxene phenocrysts are unzoned. In trachyandesite, the clinopyroxene phenocrysts can be classified into three groups: normal zoned, oscillatory zoned and unzoned. Similarly, unzoned and reverse zoned clinopyroxene phenocrysts are the two main structures in rhyolites. According to the major element contents and distinct distribution patterns of rare earth elements (REEs), we identify various clinopyroxene domains in their host volcanic rocks. Type 1 clinopyroxene domains in basalts and trachyandesites are dark, have high Mg# values and are strongly depleted in light REEs (LREEs) with no significant Eu anomalies. The Type 2 clinopyroxene domains in basalts and trachyandesites and all clinopyroxene phenocrysts in andesites are bright, have low Mg# values and are strongly depleted in LREEs and have significant negative Eu anomalies. Clinopyroxene domains in rhyolites have significant negative Eu anomalies and can be divided into two types: Type 1 clinopyroxene domains are characterized by strong depletion in LREEs, Sr, P and high field strength elements (HFSEs), while Type 2 clinopyroxene domains are slightly depleted in LREEs and have small negative P anomalies. The continuously changing major element composition and parallel distribution of trace element spider diagrams suggest that all these clinopyroxene phenocrysts in the studied volcanic rocks were derived from co-genetic magmas and the compositional transition of clinopyroxene from basalts to rhyolites attributed to different extents of fractional crystallization of various minerals (e.g., clinopyroxene, orthopyroxene, plagioclase and apatite). The oscillatory zoned and reversed zoned clinopyroxene phenocrysts show that magma mixing and recharge events with co-genetic magmas are common in the middle Okinawa Trough magma system. The origin of clinopyroxene phenocrysts involves contributions from subducted sedimentary components of 2.5% sediment melts and 1.5% sediment fluids and is deduced based on the equilibrium melts of clinopyroxene phenocrysts in basalts. The geochemical study of clinopyroxene provides evidence for the contributions of magmatic processes and slab subduction to the petrogenesis of Okinawa Trough volcanic rocks.

Characterization of the Genome Feature and Toxic Capacity of a Bacillus wiedmannii Isolate From the Hydrothermal Field in Okinawa Trough

The Bacillus cereus group is frequently isolated from soil, plants, food, and other environments. In this study, we report the first isolation and characterization of a B. cereus group member, Bacillus wiedmannii SR52, from the hydrothermal field in the Iheya Ridge of Okinawa Trough. SR52 was isolated from the gills of shrimp Alvinocaris longirostris, an invertebrate species found abundantly in the ecosystems of the hydrothermal vents, and is most closely related to B. wiedmannii FSL W8-0169. SR52 is aerobic, motile, and able to form endospores. SR52 can grow in NaCl concentrations up to 9%. SR52 has a circular chromosome of 5,448,361 bp and a plasmid of 137,592 bp, encoding 5,709 and 189 genes, respectively. The chromosome contains 297 putative virulence genes, including those encoding enterotoxins and hemolysins. Fourteen rRNA operons, 107 tRNAs, and 5 sRNAs are present in the chromosome, and 7 tRNAs are present in the plasmid. SR52 possesses 13 genomic islands (GIs), all on the chromosome. Comparing to FSL W8-0169, SR52 exhibits several streaking features in its genome, notably an exceedingly large number of non-coding RNAs and GIs. In vivo studies showed that following intramuscular injection into fish, SR52 was able to disseminate in tissues and cause mortality; when inoculated into mice, SR52 induced acute mortality and disseminated transiently in tissues. In vitro studies showed that SR52 possessed hemolytic activity, and the extracellular product of SR52 exhibited a strong cytotoxic effect. These results provided the first insight into the cytotoxicity and genomic feature of B. wiedmannii from the deep-sea hydrothermal environment.

沖縄トラフ伊平屋北部海嶺からの腹足類 2 新種の追加

沖縄トラフ伊平屋北部海嶺からの腹足類 2 新種の追加

Geochemical and Sr-Nd-Pb isotopic compositions of volcanic rocks from the Iheya Ridge, the middle Okinawa Trough: implications for petrogenesis and a mantle source

As an active back-arc basin, the Okinawa Trough is located in the southeastern region of the East China Sea shelf and is strongly influenced by the subduction of the Philippine Sea Plate. Major element, trace element and Sr-Nd- Pb isotopic composition data are presented for volcanic rocks from the Iheya Ridge (IR), the middle Okinawa Trough. The IR rocks record large variations in major elements and range from basalts to rhyolites. Similar trace element distribution characteristics together with small variations in 87Sr/86Sr (0.703 862–0.704 884), 144Nd/143Nd (0.512 763–0.512 880) and Pb isotopic ratios, demonstrate that the IR rocks are derived from a similar magma source. The fractional crystallization of olivine, clinopyroxene, plagioclase, and amphibole, as well as accessory minerals, can reasonably explain the compositional variations of these IR rocks. The simulations suggest that approximately 60% and 75% fractionation of an evolved basaltic magma can produce trace element compositions similar to those of the intermediate rocks and acid rocks, respectively. The analysis of their Sr-Nd-Pb isotopic content ratios suggest that the source of the rocks from the IR is close to the depleted mantle (DM) but extends to the enriched mantle (EMII), indicating that the mantle source of these rocks is a mixture between the DM and EMII end members. The simulations show that the source of the IR volcanic rocks can be best interpreted as the result of the mixing of approximately 0.8%–2.0% subduction sediment components and 98.0%–99.2% mantlederived melts.

Comparative metagenomic analysis of the microbial communities in the surroundings of Iheya north and Iheya ridge hydrothermal fields reveals insights into the survival strategy of microorganisms in deep-sea environments

Abstract In this study, metagenomic analysis was performed to investigate the taxonomic compositions and metabolic profiles of the microbial communities inhabiting the sediments in the surroundings of Iheya North and Iheya Ridge hydrothermal fields. The microbial communities in four different samples were found to be dominated by bacteria and, to a much lesser extent, archaea belonging to the phyla Proteobacteria, Actinobacteria, Planctomycetes, Firmicutes, Deinococcus-Thermus, and Nitrospirae, which play important roles in the cycling of carbon, nitrogen, and sulfur. All four microbial communities (i) contained chemoautotrophs and heterotrophs, the former probably fixed CO 2 via various carbon fixation pathways, and the latter may degrade organic matters using nitrate and sulfate as electron acceptors, (ii) exhibited an abundance of DNA repair genes and bacterial sulfur oxidation mediated by reverse sulfate reduction, and (iii) harbored bacteria and archaea involved in anaerobic methane oxidation via intra-aerobic denitrification and reverse methanogenesis, which were found for the first time in hydrothermal areas. Furthermore, genes involved in DNA repair, reductive acetyl-CoA pathway, and ammonia metabolism were possibly affected by distance to the vent fields. These findings facilitate our understanding of the strategies of the microbial communities to adapt to the environments in deep sea areas associated with hydrothermal vents.

Characteristics of the cultivable bacteria from sediments associated with two deep-sea hydrothermal vents in Okinawa Trough.

In this study, different culture-dependent methods were used to examine the cultivable heterotrophic bacteria in the sediments associated with two deep-sea hydrothermal vents (named HV1 and HV2) located at Iheya Ridge and Iheya North in Okinawa Trough. The two vents differed in morphology, with HV1 exhibiting diffuse flows while HV2 being a black smoker with a chimney-like structure. A total of 213 isolates were identified by near full-length 16S rRNA gene sequence analysis. Of these isolates, 128 were from HV1 and 85 were from HV2. The bacterial community structures were, in large parts, similar between HV1 and HV2. Nevertheless, differences between HV1 and HV2 were observed in one phylum, one class, 4 orders, 10 families, and 20 genera. Bioactivity analysis revealed that 25 isolates belonging to 9 different genera exhibited extracellular protease activities, 21 isolates from 11 genera exhibited extracellular lipase activities, and 13 isolates of 8 genera displayed antimicrobial activities. This is the first observation of a large population of bacteria with extracellular bioactivities existing in deep-sea hydrothermal vents. Taken together, the results of this study provide new insights into the characteristics of the cultivable heterotrophic bacteria in deep-sea hydrothermal ecosystems.

Microbial diversity in the deep-sea sediments of Iheya North and Iheya Ridge, Okinawa Trough

In this study, we analyzed the bacterial and archaeal diversities of the deep-sea sediments in Iheya North and Iheya Ridge, Okinawa Trough, using the high-throughput sequencing technology of Illumina MiSeq 2500 platform. Four samples (IN1, IN2, IR1 and IR2) were used in this study, of which IN1 and IN2 were located at regions close to and distant, respectively, from the active hydrothermal vents in Iheya North, while IR1 and IR2 were located at regions close to and distant, respectively, from the active hydrothermal vents in Iheya Ridge. The four samples were rich in different metal elements. Sequence analysis based on the V3–V4 regions of 16S rDNA gene obtained 170,363 taxon tags, including 122,920 bacterial tags and 47,433 archaeal tags, which cover 31 phyla, 50 classes, 59 orders, 87 families, and 138 genera. Overall, the microbial communities in all samples were dominated by bacteria, in which Proteobacteria was the largest phylum, followed by Chloroflexi, Firmicutes, Acidobacteria, Actinobacteria, Gemmatimonadetes, and Nitrospirae, which together accounted for 64.6% of the total taxon tags. In contrast to the high bacterial diversities, the archaeal diversity was low and dominated by Thaumarchaeota, which accounted for 22.9% of the total taxon tags. Comparative analysis showed that (i) IN2 and IR2 exhibited more microbial richness than IN1 and IR1, (ii) IR1 and IR2 exhibited higher microbial diversities than IN1 and IN2, (iii) samples from Iheya Ridge and Iheya North fell into two groups based on principle component analysis. Furthermore, microbes potentially involved in sulfur, nitrogen, and metal metabolism and cycling were detected in all samples. These results provide for the first time a comparative picture of the microbial diversities in the sediments of Iheya North and Iheya Ridge and indicate that geological features and distance from active hydrothermal vents likely play important roles in the shaping of microbial community structure.

Genomics of deep‐sea and sub‐seafloor microbes

Over two‐thirds of the surface of the earth is covered by oceans, which have an average depth of about 3800 m. As each drop of ocean water contains > 105 cells, the > 1030 microbial cells in the ocean represent the largest reservoir of microbes on earth (Whitman et al., 1998). Communities of bacteria, archaea, protists and unicellular fungi account for most of the oceanic biomass and metabolism. Marine microbes are known to play an essential role in the global cycling of nitrogen, carbon, oxygen, phosphorous, iron, sulfur and trace elements (Karl, 2007).

Rhodotorula pacifica sp. nov., a novel yeast species from sediment collected on the deep-sea floor of the north-west Pacific Ocean

A novel species of the genus Rhodotorula was isolated from sediments collected on the deep-sea floor in the north-west Pacific Ocean. Strains SY-96T, isolated from the Yap Trench, and SY-246, isolated from the Iheya Ridge, had almost identical nucleotide sequences for their internal transcribed spacers and their 5.8S rDNA. Their physiological characteristics were also almost identical. The strains were assumed to be related to Rhodotorula mucilaginosa and Rhodotorula dairenensis based on sequence similarities in the D1/D2 region of the 26S rDNA. The low DNA-DNA relatedness and sequence similarity between strain SY-96T and related species revealed that strains SY-96T and SY-246 represent a hitherto unknown species. As ballistoconidia and sexual reproduction were not observed in strains SY-96T and SY-246, these strains are described as Rhodotorula pacifica sp. nov. The type strain is SY-96T (= JCM 10908T = CBS 10070T).

Spongicoloides Iheyaensis, a New Species of Deep-Sea Sponge-Associated Shrimp from the Iheya Ridge, Ryukyu Islands, Southern Japan (Decapoda: Stenopodidea: Spongicolidae)

A new species of the deep-sea sponge-associated shrimp genus Spongicoloides Hansen, 1908, S. iheyaensis, is described and illustrated on the basis of 6 specimens (3 sexual pairs) collected from the North Knoll of the Iheya Ridge at depths of 988-1051 m, Ryukyu Islands, southern Japan. This is the fourth species of the genus known from the Pacific Ocean. The new species is similar to S. hawaiiensis from Hawaii and S. novaezelandiae from New Zealand, but is distinguished by the differences in spination of carapace, sixth pleonal somite, and third pereiopod. It is suggested that the egg number of the new species is greater than that of other congeneric species. Sexually dimorphic characters are discussed. A key to the Pacific species of Spongicoloides is provided.

TEM Observations of Chemosynthetic Bacteria in the Deep-sea Hydrothermal Vents and Seep Organisms

Symbiosis of chemoautrophic bacteria with the members of hydrothermal vent and cold seep communities in the deep-sea were examined by histology using transmission electron microscopy; Bathymodiolus spp. from Sagami Bay, the Iheya Ridge and the North Fiji Basin; and Ifremeria nautilei from the North Fiji Basin. Two species of Bathymodiolus, each from Sagami Bay and the Iheya Ridge harbored methane-oxidizing symbionts within their gill tissues. Vent gastropod Ifremeria nautilei from the hydrothermal vents of the North Fiji Basin housed two types of symbionts; one sulfur-oxidizing type and the other methane-oxidizing type. The occurrence of chemosynthetic symbionts in these organisms were expected before-hand based on the ecological observations of their habit. The other members of these groups from world oceans and the recent advances in the symbiosis of the vent and seep communities were reviewed.

Methanothermococcus okinawensis sp. nov., a thermophilic, methane-producing archaeon isolated from a Western Pacific deep-sea hydrothermal vent system.

A novel thermophilic, methane-producing archaeon was isolated from a deep-sea hydrothermal vent chimney at the Iheya Ridge, in the Okinawa Trough, Japan. The cells were highly motile, irregular cocci, with a polar bundle of flagella. Growth was observed between 40 and 75 degrees C (optimum 60-65 degrees C; 30 min doubling time) and between pH 4.5 and 8.5 (optimum pH 6.7). The isolate was a strictly anaerobic autotroph capable of using hydrogen and carbon dioxide as sole sources of energy and carbon. Formate can serve as an alternative energy source. The G+C content of the genomic DNA was 33.5 mol%. Phylogenetic analysis based on 16S rDNA sequences and DNA-DNA hybridization analysis indicated that the isolate was closely related to members of the genera Methanococcus and Methanothermococcus. This isolate, however, could be differentiated from the previously described species of these genera on the basis of its physiological and molecular properties. The name Methanothermococcus okinawensis sp. nov is proposed, with the type strain IH1T (=JCM 11175T=DSM 14208T).

Oceanobacillus iheyensis gen. nov., sp. nov., a deep-sea extremely halotolerant and alkaliphilic species isolated from a depth of 1050 m on the Iheya Ridge

An extremely halotolerant and alkaliphilic bacterium was isolated previously from deep-sea sediment collected at a depth of 1050 m on the Iheya Ridge. The strain, designated HTE831 (JCM 11309, DSM 14371), was Gram-positive, strictly aerobic, rod-shaped, motile by peritrichous flagella, and spore-forming. Strain HTE831 grew at salinities of 0–21% (w/v) NaCl at pH 7.5 and 0–18% at pH 9.5. The optimum concentration of NaCl for growth was 3% at both pH 7.5 and 9.5. The G+C content of its DNA was 35.8%. Low level (12–30%) of DNA–DNA relatedness between strain HTE831 and the species of these genera was found, indicating that HTE831 could not be classified as a member of a new species belonging to known genera. Based on phylogenetic analysis using 16S rDNA sequencing, chemotaxonomy, and the physiology of strain HTE831, it is proposed that this organism is a member of a new species in a new genus, for which the name Oceanobacillus iheyensis is proposed.

Rare earth element geochemistry of hydrothermal deposits and Calyptogena shell from the Iheya Ridge vent field, Okinawa Trough.

Although the rare earth element (REE) geochemistry of hydrothermal systems have intensively been investigated at mid-oceanic ridges, studies are relatively few at the converging plate zones like the Okinawa Trough. The “chimney” deposits obtained by using submersible “SHINKAI 2000” from the Iheya Ridge site, Okinawa Trough are largely composed of massive carbonates and silicates with minor amounts of sulfides, and appear black and white depending upon their composition. The concentrations of REEs are 2–3 orders of magnitude higher in the sulfide-rich black portion than in the white portion. Both deposits show a pronounced positive Eu anomaly and the light REE enrichment which are characteristic of the high-temperature fluids venting from sediment-free oceanic ridges. Whilst the Okinawa Trough REE data are unique in the hydrothermal vent systems in having a flat chondrite-normalized pattern for the REEs heavier than Tb. The Eu-anomaly is greater in the white deposit than in the black deposit, suggesting that Eu2+ is more mobile (resistant to scavenging by sulfides) than stricktly trivalent REEs in the hydrothermal solution and may be incorporated into the former by substitution of Sr2+ in the calcite lattice. The Calyptogena shell shows the REE pattern typical for seawater without any positive Eu anomaly, suggesting that the influence of hydrothermal solution is negligible. Although the light REE concentrations are comparable, the heavy REEs are significantly higher in the shell than in the white deposit. This suggests that the concentrations of the heavy REEs in the carbonate-forming hydrothermal solution may be lower than those of ambient seawater. Thus, the hydrothermal system in the Okinawa Trough may not be a source but a sink for dissolved REEs in seawater.

Submersible Observations of the Hydrothermal Vent Communities on the Iheya Ridge, Mid Okinawa Trough, Japan

During the Dives Nos. 409, 410, 480 and 481 of the Japanese submersible Shinkai 2000, conducted on June 10 and 11, 1989 and on May 16 and 17, 1990, several hydrothermal vents and prosperous vent associated biological communities were found on the northern slope of the Iheya Ridge in the Mid-Okinawa Trough (27°32.5′ N, 126°58.5′ E: depth 1,400 m). The first site we found, the “Calyptogena Site”, was characterized by a relatively thick blanket of sediments, pleated and/or laminated lava flows, with occasional lobate pillows and white and yellow stains. Although no remarkable shimmering water and thermal anomalies were detected during the observations, the extraordinarily dense community must be related to hydrothermal activities. The community was dominated by the giant white clam, Calyptogena okutanii, in biomass, and by Neolepas-type primitive scalpellids and slender vestimentiferan tube-worms in number. The second site, the “Pyramid Site”, situated only 200 m northward from the Calyptogena Site has typical clear smokers emitting hot water over 200°C, and is characterized by a hard substratum of volcanic rocks and hydrothermal slabs. No noteworthy succession was perceived at the Calyptogena Site over a year. Many of the vent members occurred at both sites. However, Calyptogena okutanii, which were confined to the sediment bottom, Neolepas spp. and larger vestimentiferan tube-worms were found to thrive only at the Calyptogena Site, being only minor elements in the Pyramid Site. The global distribution of several groups of organisms is discussed preliminarily in zoogeographical terms based on comparison with other submersible missions and surveys done by surface vessels.

Gastropod Fauna of a Thermal Vent Site on the North Knoll of Iheya Ridge, Okinawa Trough

Gastropod Fauna of a Thermal Vent Site on the North Knoll of Iheya Ridge, Okinawa Trough

伊平屋海嶺に見られる針状鉱物について

Dive #857 by “SHINKAI 2000” was carried out at Iheya Ridge of Okinawa Trough in April of 1996 to collect deepsea sediments and rocks. Some rocks collected near hydrothermal vents were covered by white microbial mats. Detailed studies by optical microscope, scanning electron microscope, fluorescence microscope, energy dispersion X-ray analysis and X-ray diffraction analysis showed that the white microbial mats consisted of a lot of needle-like quartz crystals and spherical materials . The spherical materials existed around quartz crystals. It can be considered that they influence the formative period of these crystals.

伊平屋海嶺熱水噴出孔に棲息する微生物

Electron microscopic studies were undertak en in order to observe microorganisms on the basis of the both current hydrothermal fluid and a dead sulfides chimney's samples collected at the North Knoll of Iheya Ridge, Okinawa Trough by “Shinkai 2000” dives. As a result, both adhesive cocci and bacilli were observed in isolated or connected situation by SEM, which were recognized to adsorb S by EDX. Other studies with SEM-EDX recognized cocci and bacilli floating in the hydrothermal fluids acknowledged as “clear smokers”. These bacteria were crystallised with the elements of S and Ba. Further studies with TEM identified that bacteria adsorbed barite on the cell membrane. A range of results of microscopy sug-gest that bacteria which are considered to be S-Oxidizing Bacteria, are offering the site of producing barite.