Biomolecules such as nucleic acids, enzymes, antibiotics participate in a variety of biochemical processes and play vital roles in life activities or microbial community relating to genetic transfer, disease control, and transformation of nutrients and pollutants. In terrestrial environments like soil, biomolecules usually interact intimately with clay minerals which are the finest and the most active inorganic components. The binding of biomolecules on clay minerals have profound influences on their activity and fate in the environments. Significant progresses have been made over the past decades with respect to the adsorption and activity of DNA, enzymes and antibiotics on clay minerals and soil clays. The influences of clay minerals are dependent on the nature and the type of minerals as well as biomolecules. In order to obtain a thorough understanding of clay-biomolecule interactions, some advanced techniques such as atomic force microscopy, isothermal microcalorimetry, synchrotron radiation are expected to shed new lights on the mechanisms of the formation of soil clay-biomolecule complexes at the molecular level. More researches on natural soil clays are needed and studies that are directed to applied fields deserve close attention.

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The smectite-illite (SI) reaction is a ubiquitous process in siliciclastic sedimentary environments. For the last 4 decades the importance of smectite to illite (S-I) reaction was described in research papers and reports, as the degree of the (S-I) reaction, termed "smectite illitization", is linked to the exploration of hydrocarbons, and geochemical/petrophysical indicators. The S-I transformation has been thought that the reaction, explained either by layer-by-layer mechanism in the solid state or dissolution/reprecipitation process, was entirely abiotic and to require burial, heat, and time to proceed, however few studies have taken into account the bacterial activity. Recent laboratory studies showed evidence suggesting that the structural ferric iron (Fe(III)) in clay minerals can be reduced by microbial activity and the role of microorganisms is to link organic matter oxidation to metal reduction, resulting in the S-I transformation. In abiotic systems, elevated temperatures are typically used in laboratory experiments to accelerate the smectite to illite reaction in order to compensate for a long geological time in nature. However, in biotic systems, bacteria may catalyze the reaction and elevated temperature or prolonged time may not be necessary. Microbes and clay minerals coexist in shales, siltstones, and sandstones under diagenetic conditions. Metal reducing microbes have been discovered in sedimentary rocks from great depths (2,700 meters below the land surface) and in various hot environments (up to 90-100℃). These are similar conditions under which clay minerals undergo transformations. Under these conditions, thermophilic and hyperthermophilic bacteria can "witness" and actively participate in clay diagenesis. Abundant and viable microbes (10^4-10^5 cells/g) have been found inorganic-rich shales. Microbes may be more abundant and active in shales at the onset of clay diagenesis and in shales under the "overpressure" condition, where there exists significant porosity and permeability. Microbially promoted S-I conversion represents a previously unidentified mechanism. The role of microbes, therefore, should be considered in the study of clay mineral diagenesis. Despite the important role of microbe in S-I reaction, factors that control the reaction mechanism are not clearly addressed yet. This paper, therefore, overviews the current status of microbially mediated smectite-to-illite reaction studies and characterization techniques.

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Palygorskite was found as a clay vein in the Futamata area in northeastern Hokkaido, Japan. A light yellowish pink palygorskite vein was observed within a vertical joint in conglomerate of the Upper Eocene-Lower Oligocene Rikubetsu Formation in the Futamata landslide area. The palygorskite is considered to have crystallized from a low-temperature hydrothermal solution related to the volcanic activity of the Lower Oligocene Futamata Andesites.

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The adsorption of formaldehyde by sepiolite-amino acid complex (sepiolite combined with an amino acid) was studied in comparison with that of the aldehyde by mere sepiolite. The formaldehyde adsorption isotherms were measured at 25℃ in ambient atmosphere. The adsorptivity of sepiolite-amino acid complex was about 10 times greater than that of mere sepiolite at a low equilibrium concentration (< 1 ppm). However, amino acid itself did not react with formaldehyde. Adsorbents such as sepiolite and activated carbon also have a very small formaldehyde adsorption capacity. We have developed a formaldehyde adsorbent sheet, which is made of a mixture of pulp and sepiolite-amino acid complex. The sheet have put into practical use globally as a scavenger to remove formaldehyde in ambient air.

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