Biomineralization of Layer Silicates and Hydrated Fe/Mn Oxides In Microbial Mats: An Electron Microscopical Study

Abstract

Abstract--The formation of layer silicates on capsuled bacterial cell walls was studied in freshwater microbial mats. The trends associated wtih A1, Si, Mn and Fe deposits with capsules are consistent with occurrence of layer silicates with 14, 10 and 7 A X-ray diffraction (XRD) patterns. Scanning electron microscope and transmission electron microscope (SEM and TEM) observations of the microbial mats revealed the presence of microcolonies of rod-and coccus-shaped bacteria with layer-silicate thin films. Field measurements of pH, temperature and Eh indicated that these conditions for bacterial crystallization of layer silicates and hydrated Fe/Mn oxides in freshwaters are as follows: pH 6.3 to 7.8, 12 to 20 ~ and Eh -24 to +200 mV. Glass slides kept for 3 weeks in the beakers with natural freshwater and river sediments were coated with brown materials. These materials were identified as layer silicates and colonized bacteria formed under photosynthetic conditions. The well-developed holdfasts on Leptothrix discophora bacterial cells are mainly associated with poorly crystalline layer silicates and hydrated Fe-Mn oxides. Semiquantitative elemental analyses of holdfasts using energy-dispersive X-rays (EDX) indicated that layer-silicate crystallization covers the cell at an early stage. Iron and manganese crystallization develops at a later stage, where aluminum substitution occurs in crystal structures. Laboratory experimental results indicated that layer silicates grew from a biochemical origin, rather than from inorganic origins in freshwater. Layer-silicate formation is linked with bacteria in microbial mats.

Mass occurrence of benthic coccoid cyanobacteria and their role in the production of Neoarchean carbonates of South Africa

“…It has been found (e.g. Ferris et al, 1987;Konhauser et al, 1994;Urrutia and Beveridge, 1994;Schultze-Lam et al, 1995;Fortin et al, 1997;Tazaki, 1997;Barker and Banfield, 1998;Douglas and Beveridge, 1998) that an array of authigenic minerals, including clay minerals, can nucleate and grow within the extracellular matrices. It is also significant for the present discussion, that microprobe analyses of calcified modern coccoid cyanobacterial mats forming huge, towerlike calcareous structures in the highly alkaline Lake Van, Turkey (Kempe et al, 1991) show elemental composition (Fig.…”

“…10) indicate that, as in the case of modern bacterial cells, they have been mineralized by Al-K-Fe silicates with an admixture of Fe oxides (Tazaki, 1997). It has been shown that bacterial surfaces are good sorption interfaces for Al-K-Fe silicate ions (Urrutia and Beveridge, 1994;Tazaki, 1997).…”

Microbial Formation of a Halloysite-Like Mineral

“…Theng and Orchard (1995) discussed the physical and chemical 4 interaction between microorganisms and soils in the ecosystems. Bio-mineralization of kaolinite, nontronite, and bentonite on living cells of microorganism in natural and cultivated systems have been reported (Tazaki, 1997;Ueshima et al, 2000;Asada and Tazaki, 2000;Tazaki, 2000). The degree of mineralization in these examples ranged from poorly crystalline granules to well oriented crystalline solids.…”

Formation of Banded Iron-Manganese Structures by Natural Microbial Communities

“…Widespread bacterial fixation of metallic ions contributes to immobilization of mineral-forming elements through a continuum of reactions involving sorption and authigenic mineral precipitation (Ferris et al, 1987;Emerson and Revsbech, 1994;Tazaki, 1997;Tazaki et al, 1998). Holden (1998) reported ancient zebra patterns in a 30 million year old limestone from Germany, and stated that inorganic processes could produce the magnificent patterns observed.…”