Microbial Formation of Imogolite(Clay-Biology Interface,Proceedings of the 13^<th> International Clay Conference)

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The interaction between clays and microbes was investigated from field on pumice and imogolite in volcanic ash soils collected from Kurayoshi Pumice in Tottori, Japan. In comparison to laboratory studies on microbial films of cultures derived from fresh water system were examined. Observation of DAPI stained films revealed that numerous microbes have found in the system. Optical and electron microscopic observations of microbes showed that the imogolite films encrusted with areas of the bacterial cells. XRD of the films showed a 1.4, 0.82, 0.55, and 0.33nm d-spacing consistent with a imogolite (OH)_3Al_2O_3SiOH. EDX analysis revealed that the films were mainly composed of Al, Si, and Fe elements. FT-IR analysis exhibited the characteristic adsorption bands of clays for O-H (3400cm^<-1>), H-O-H (1650cm^<-1>) and Si-O-Al (1000 and 950cm^<-1>) and organic materials for C-H-COOH (3000cm^<-1>) and CNH (1200 and 1500cm^<-1>). The imogolite films contain higher concentration of nitrogen (0.08 wt%), carbon (2.20 wt%), and sulfur (0.11 wt%) than that of pumice in the same volcanic ash soils, suggesting that the imogolite was closely associated with adhesive organics. Scanning electron microscopy (SEM) showed a variety of bacterial- like forms both in the natural volcanic ash soils and cultured water system. Transmission electron microscopy (TEM) revealed extensively mineralized bacterial cells with fibrous network structure of imogolite formed on both coccus and bacillus type bacterial cells, showing electron diffraction pattern of a diffuse halo at the initial stage. The well-developed bio-films show lattice images of dehydrated imogolite with 1.0-1.1nm d-spacings. The present investigation strongly suggests that imogolite was interacted with bacterial cohesion as a bio- organic clay product. The identity of the bacteria responsible for bio- imogolite formation is unknown, but microorganisms living in the films make an important role as a nucleation site for the formation of imogolite in volcanic ash soils. The bio-imogolite may have been formed from biochemical weathering products of cohesive materials, which subsequently controlled the formation of clay-organic complexes.
日本粘土学会の論文

Microbial Formation of Imogolite(Clay-Biology Interface,Proceedings of the 13^<th> International Clay Conference)

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