Molecular phylogeny is one of the important methods for understanding the pattern and process of biological evolution independently of morphological data. Molecular phylogenetic analysis, however, provides no sufficient information on phylogenetical changes of morphology throughout the geological time. It is generally difficult to select the most optimum tree among various kinds of molecular phylogenetic trees described with a variety of techniques, and is also difficult to demonstrate directly the phylogenetic relation between ancestors and descendants simply in molecular phylogenetic analysis. Therefore, the stratigraphical information and morphological one are indispensable for the evolutional comprehension of morphological changes.

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 Electron microscopic observations of green biomats and deposits from the Kotelnikovsky Hot Springs (pH 8.0) located on the northwest coast of Lake Baikal, Russia, showed variety of fossilized microorganisms. The energy dispersive X-ray fluorescence (ED-XRF), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) microspectroscopy, and scanning electron microscopy equipped with energy dispersive X-ray (SEM-EDX) analyses revealed that the biomats and deposits were rich in silicon and calcium suggesting fossilization processes. The XRD analysis identified the amorphous silica with diffused peak at 4.1Å associated with quartz (SiO₂) with main peaks at 3.34 and 4.25Å, calcite (CaCO₃) with main peak at 3.04Å, and fluorite (CaF₂) with main peaks at 3.15, 1.92-1.93, and 1.65Å. The SEM-EDX analyses successfully detected fossilized microorganisms in the hot spring biomats and deposits. The content of sulfur as well as Ca/K and P/S ratios considerably differed between the bacterial cells and amorphous particles. The SEM-EDX analyses of green biomats showed Ca/K ratio could be shifted during fossilization process, because the ratio was found to be 0.7 for the bacterial cells and 2.1 for fossilized microorganisms. The FT-IR results indicated the fossilization process of bacteria from green biomats to deposits, decreasing organic compounds (C-H, C-N-H, N-H bonds) and increasing silica-organic bonding (Si-O-Si and Si-O). Silicification and calcification of the microorganisms extensively appeared in the biomats and deposits under pH 8.0 hydrothermal conditions.

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