Morphological characteristics of ammoniojarosite and argentojarosite formed through mediation of iron-oxidizing bacteria, Thiobacillus ferrooxidans, were studied, compared with those of chemical products. The scanning electron microscopic observations (SEM) indicated that biologically mediated ammoniojarosite and argentojarosite consisted of aggregates of many approximately squared-faced crystals with shape edges and submicrometric microintergrowths. They were very similar to morphologies of chemically formed ammoniojarosite with slow oxidation of Fe(II) ions. However, chemically formed argentojarosite (with rapid and slow oxidation of Fe(II) ions) and ammoniojarosite (with rapid oxidation of Fe(II) ions) consisted of several micrometric large particles with smooth surfaces, completely different from the biologically mediated products. It was found that the morphological characteristics of jarosite groups formed through biological mediation were dependent on slow oxidation of Fe(II) ions and slow crystallization of ammoniojarosite, not but on extracellular substances of T. ferrooxidans.

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Recently, biological techniques have been reported on the recovery and accumulation of gold from solutions containing auric complex ions. The Galvanic cell used aqueous and juicy solution of spinach leaves, a biological electric cell, was made out. In this preliminary report, the accumulation of gold by bacteria was recognized in a part of the experimental systems in which auric complex ions were gradually added into the spinach solutions. Pseudomonas putida was predominantly identified in a sample accumulating gold.

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The variation of iron chemical forms during the teeth formation of chiton was clarified by utilizing the fluorescence XAFS technique. Fe K-XANES spectra of the teeth of chiton in various maturation stages show a complex oxidation/reduction process of iron during the teeth formation. In the earliest stage of the maturation, an amorphous ferritin-like ferric compound accumulates in the teeth. Magnetite formation occurs abruptly in the next maturation stage, and the color of the teeth changes from reddish brown to gray. The spectra of the teeth in the latter maturation stages show that the edge-energy is higher than that of magnetite. These results suggest that the fully mineralized teeth are considered to be a mixture of magnetite and a ferric compound.

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Calcium phosphate is a main inorganic constituent of bone, which can be interpreted as a composite material of calcium phosphate and collagen. This calcium phosphate shows a similar chemical composition with hydroxyapatite (HAP). Many devices with HAP have been developed for medical use because of its excellent biocompatibility. The hardness of HAP is adequate to supportive and protective functions in the skeleton and it also plays an important roll as homeostatic regulator of Ca and PO₄ in the blood and other body fluids. The regulation process is closely connected to the remodeling of bone. Bone is renewed and reconstructed throughout the lifetime of the individual and therefore, HAP as biomaterial should be compatible to this dynamic remodeling process. We developed a new technology to control the pore size in HAP. The size of pore was controlled by applying HAP powder of nm-size and nylon- and acryl-monofilaments. The HAP processed with nylon-monofilament (f=80μm) showed the similar micro-pores to those of the Haversian canal in the natural bone. This porous HAP can be applied to a biofilter and a drug-delivery system.

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Algal biomineralization prevails in low temperature environmental condition. Microbial mats taken from the Lake Vanda and Onyx river at Victoria Land, Antarctica, showed the presence of nanometer sized barite (BaSO₄) crystals with alga. The temperature measured at the surface of water was 3°C and at 70 m depth was 20°C. Acidity increased gradually with depth in Lake Vanda, with pH ranging from 8.0 at the surface to 6.0 at the bottom. The bottom sediments contains up to 11.2 mg, kg^-1 H₂S. An Eh calculated from the redox couple SO₄/H₂S at 70 m depth is-0.13V, suggesting that the measured Eh of -0.1 V is reasonable, assuming that there is sufficient algal reduction of SO₄. TEM, SEM and EDX studies reveal the mechanisms of crystal growth of barite associated with alga. TEM photographs show the embryonic matter coated with hydrated thin films is essentially crystalline, having layer spacings characteristic of barite. These phenomena depend upon the low pH condition and the activites of alga. SO₄ transport from the solution into the algal cell walls are remarkable for their ability to produce barite. Microbial mats are an important agent in the algal biomineralization. The sedimentary distribution of barite following deposition was controlled by the presence of the mats at the sediment-water interface. The stimulation of algal activities causes preservation of the colonial forms as minerals. When the mats die, barite grains are released to the sediment pore waters. We can actually determine whether the mineral is biogenic or not, based on the chemistry, the mineralogical structure, the shape and the surface morphology, even where there is much less direct evidences that microorganisms are present.

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Laboratory experimental simulation under natural conditions show that activity of microorganisms involved in precipitation of iron and manganese minerals. Brown or black precipitates were experimentally formed on the slide glass which was kept in a beaker with the water and sediment from the Omma Formation. These precipitates were examined by optical microscope, scanning electron microscope, energy dispersive X-ray spectrometer, transmission electron microscope, and X-ray powder diffractometer. These precipitates were identified as iron mineral and buserite accumulated by microorganisms. This study revealed that precipitation of iron and manganese minerals were closely related to microbiological activity, and was useful to understand formation processes of these deposit.

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The silica sinter of the Nakabusa Hot Spring in Nagano Prefecture, Central Japan, represents the morphology of stromatolite. Filamentous bacteria are living in the hot spring water. Some silica sinter was formed by silica sticking to the filamentous bacteria. No photosynthetic activities were at work in the filamentous bacteria. So, it is suggested that the morphology of stromatolite is not enough proof of its formation at the shallow bottom of the sea, where living bodies could photosynthesize with sunlight. Even when developed stromatolite structures are found, it is necessary to discuss whether those structures are biogenic or abiotic, and in the case of biogenic structures, photosynthetic or non-photosynthetic.

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The damage by upheaval of the residential land of houses built on the mudstone of the Miocene has been reported in Iwaki-city area, Fukusima prefecture, Japan. The present studies were performed intending to clarify the reasons why the land was upheaved. When the fresh mudstone was added to the culture medium for Thiobacillus novellus supplemented with sodium sulfide, the pH of the medium decreased from 8 to 3.2 during 7 day-cultivation at 28°C. When the mudstone was added to the medium for Thiobacillus ferrooxidans in which ferrous sulfate was replaced by powdered pyrite and pH was adjusted to 7, the pH of the medium decreased from 7 to 2, and the concentrations of ferrous and ferric ions in the medium greatly increased. When the mudstone sterilized at 121°C for 20 min was used, neither the decrease of the pH nor the increase in the concentrations of ferrous and ferric ions was observed. Therefore, the microorganisms, sulfur oxidizing and acidophilic iron oxidizing bacteria, in the mudstone seemed to have oxidized pyrite to form sulfuric acid if sulfide was available, even though the initial pH of the mudstone was 7 - 8. Sulfuric acid thus formed will form gypsum which seems to be one of the causes of upheaval of the ground.

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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.

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Bacterial biomineralization of clay minerals was studied by SEM-EDX and TEM. Two kinds of samples obtained from Kutani glaze and the deep sea sediment of Iheya Basin, Okinawa Trough. Halloysite particles were observed on the cell wall of cyanobacteria in the Kutani glaze solution. Halloysite was introduced from feldspar in the processes of biomineralization by cyanobacteria. On the other hand, iron rich nontronite was formed with bacterial extraction of Mg and Al ions in the deep sea sediments, Iheya Basin. These results indicate that the formation of clay minerals depends on not only physical precipitation but also the processes of bacterial biomineralization associated with extraction of specific elements.

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Iron ores and mineral spring water from Gumma Iron Mine were examined mainly by TEM. Biomineralization was found on diatom and bacteria in the spring water, and also on living moss. Aggregates of cyanobacteria-like fossils were found in some iron ore which is composed of goethite and jarosite. They were examined by EPMA and TEM (lattice imaging). The formation mechanism of iron ore was discussed and biogenic contribution to the ore formation was suggested.

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The growing stromatolitic structures which were composed of amorphous Mn minerals were found in Yunokoya hot springs, Gumma Prefecture, Japan. These stromatolitic structures are black and brittle. The form of these structures are hemispherical. Many bacteria that were coated with amorphous Mn minerals were found on these structures. It is suggested that the formation of these structures are related to the activities of bacteria coated with amorphous Mn minerals.

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Periodic precipitation well known as the Liesegang ring has been studied for understanding the formation of periodic pattern in chemical system. On the other hand, various types of tree-like aggregates of crystals have been widely studied experimentally. Although so far these two diffusion-precipitation patterns have been separately studied based on different experiments and theories, both of them have a common nature of diffusion and crystallization. We report an interesting experiment showing a coexistence of periodic precipitation and tree-like aggregate and the transition between them. While the Liesegang band experiment using potasium iodide and lead nitrate yields periodic precipitation of lead iodide near the contact surface, tree-like aggregates appear suddenly at some distance from the contact and grow away from the contact. The position of transition varies with the agar concetration, suggesting that nucleation and growth rates as functions of agar concentration are controlling factors. This experiment will provide a new example for understanding of the transition mechanism between aperiodic pattern and a disordered pattern in nature.

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Understanding the coevolution of life and the earth's environments is one of the important subjects of the Decoding the Earth Evolution Program, a grant-in-aid scientific research for the priority areas, Ministry of Education, Japan. A large amount of stromatolites and banded iron formations has been collected for this purpose. Although many of them have been regarded as remnants of microbial mats, quite few direct evidence for microbial communities, their biogeochemical roles, or ecological settings has been preserved. Here we argue that recent microbial mats and stromatolitic structures observed in many active hot springs may provide important clues for modeling stromatolite formation processes as well as Precambrian biosphere. We present some results of chemical mapping of microbial mat sampled from hot springs in central Japan. The scanning X-ray analytical microscope we introduced here provides new and important information on the morphological and chemical structures of microbial mats.

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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.

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Except for metal-free chlorophylls (pheophytins) functioning as primary electron acceptors in purple bacteria and in photosystem II of higher plants, all the naturally occurring chlorophylls have been believed to be magnesium complexes. To clarify the reason for the choice of Mg as the central metal of chlorophylls, we have systematically studied the absorption, fluorescence and redox properties of metallo-substituted chlorophylls, and concluded that Zn-substituted chlorophylls may act as both antenna and primary electron donor of photosystems. Quite recently, we discovered novel photosynthesis using Zn-containing bacteriochlorophyll a in an acidophilic bacterium Acidiphilium rubrum. This finding indicates an unexpectedly wide variability of photosynthesis.

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