The aim of the study was to investigate the transformations of clay minerals at the laboratory experiments under the growth and fossilization of alkaline cyanobacteria. The clays incubation with cyanobacteria resulted in different trends of their transformations. The direction and intensity of transformation depends on type of clay mineral. The observed processes were fast and completed within the first 10-60 days of experiments. Cyanobacteria most actively influenced the processes of mineral dissolution and the transformations during the stage of their photosynthesis. Formation of carbonate in the experiments with palygorskite, bentonite, and kaolinite was observed at the stage of cyanobacteria fossilization.

Capacity for growth in water suspensions of volcanic ashes was shown for two oscillatorian cyanobacterial isolates from different environments. Growth dynamics depended on the physicochemical characteristics of the ashes and on pH of the medium. During cyanobacterial growth, some elements were leached, which either stimulated or inhibited growth. These solubilized elements could be adsorbed on the mucous sheaths, mineralizing the trichomes. The extracellular polysaccharides excreted by cyanobacteria facilitated adhesion between the ash particles and the changes in their composition. These results suggest an analogy between the processes in the modern volcanogenic areas and the biological weathering on volcanic soils during the early period of life on Earth.

The cyanobacterium Oscillatoria terebriformis was shown to exhibit resistance to high manganese concentrations, remaining viable at 2.5 mM MnCl2 in the medium. Cyanobacterial cells were capable of considerable manganese consumption from the medium. The dynamics of Mn sorption by the cells were the same in all experimental variants, independent of the manganese concentration. Manganese concentration in the biomass peaked after 2–3 days and depended on Mn2+ concentration in the medium and on the amount of biomass introduced. In the case of O. terebriformis, manganese removed from the medium may be subdivided into Mn absorbed by the cell, Mn bound to the cell wall, Mn absorbed by the glycocalix, and chemically precipitated Mn. Of the total 21.25 ± 1.0 mg of consumed manganese, biological absorption and chemical precipitation were responsible for 11.78 ± 0.98 and 9.2 ± 0.8 mg, respectively. In the presence of cyanobacteria, Mn removal from the medium was 2.28 times higher than in the control. This process depended considerably on Mn sorption by exopolysaccharides. At 1.3 mM Mn2+, a lamellar mat was formed with interlayers of manganese carbonate.

The mechanism of formation of specific biosiliceous lamellar deposits characteristic only for a single hot springs was investigated in the Thermofilny spring in Volcano Uzon's caldera. It is shown that the formation of such deposits is a result of the influence of three factors: the high content of silicon in water (up to 400 mg/L); the growing algobacterial mat in the spring flow, and an accumulation of gas bubbles underneath the algobacterial mats in the bed of flow. Gas bubbles from the punctures the mat layers, forming protrusions over the flow of the stream, desiccating over time. In such conditions, mat layers function as a pump, contributing to the evaporation of source water (the principle of the wick). As a result of this process, a local accumulation of flint in the raised section of the mat layers takes place (due to evaporation of water and biota fossilization), followed by a lowering of the silicified layer or its fragments to the spring bottom. The process can be repeated several times. The observed thickness of the sedimentary bio-mineral structures reached about 30 cm in the range of the hot spring. Authors propose the name "biosilicite" for a rock filled with biota.

A novel method, laser interference microscopy, has been developed for studying the morphofunctional state of bacterial cells and the structure of bacterial communities. The following potentialities of the method are shown: rapid determination of the cell structure and subcellular structures (nucleus zone, vacuoles, lamellar structures) and the physiological state of the cell, as well as the study of the structure of bacterial communities (biofilm). The method does not require any additional preparation of cells before the investigation (fixation, staining, treatment with contrasting substances), which reduces the possible appearance of artifacts to a minimum and enables one to use laser interference microscopy for in vivo investigations.

The ultrastructure of the haloalkaliphilic endoevaporite cyanobacterium ‘Euhalothece natronophila’ Z-M001 from the soda Lake Magadi was investigated during the initial stages of fossilization in a model experimental system. The cyanobacterium was cultivated in concentrated carbonate solution supplemented with calcium chloride. It was revealed that the amorphous CaCO3 formed under these conditions could interact with the cell wall during the first stages of ‘E. natronophila’ calcification. Evidence is presented that the surface layer of the ‘E. natronophila’ envelope, presumably containing polysaccharide and/or (glyco)protein components, can be involved in the adsorption and subsequent crystallization of CaCO3 with the formation of a massive “shell” embedding the morphologically intact cells. It was established that the ultrastructure of the cell wall and the intrathylakoid space changed during CaCO3 mineralization. During the later fossilization stages, cells covered by the calcium-containing “shell” were apparently mummified, and mostly retained their original shape. The encapsulation of cyanobacteria in the trona globule was characterized by a different pattern. It probably involved tight binding of the growing crystal to the glycocalyx components that are anchored in the outer membrane. This may result in its detachment from the underlying peptidoglycan layer. The peptidoglycan was retained, and the protoplasts were ultrastructurally similar to the intact ones. Cyanobacteria incorporated in large trona crystals underwent degradation, deformation, and destruction. This accounts for the fact that massive trona deposits of Lake Magadi lack cyanobacterial fossils that are abundant in calcium-containing strata.

Laboratory simulation of fossilization of cyanobacterial cells in the high-carbonate medium in the presence of calcium was carried out for the haloalkaliphilic natronophilic cyanobacterium ‘Euhalothece natronophila’ Z-M001. This organism was isolated from the Magadi soda lake, where the bioherms consisting of mineralized coccoid cyanobacteria were found in the Quaternary sediments. The structural and chemical heterogeneity of the minerals produced during this process was established, with calcium carbonate and trona being the main products. The differences in the process of cyanobacterial cell carbonatization in soda lakes and marine or freshwater systems were determined. Initial precipitation of calcium carbonate was shown to occur due to a chemical reaction not involving cyanobacteria. At the subsequent stages, amorphous CaCO 3 is sorbed and crystallized on the surface of some of the cells within a cyanobacterial population, resulting in formation of a shell-like mineral layer. The cells embedded in trona in the same system were shown to undergo deformation and destruction. In both cases the mineralized cells were shown to lose their photosynthetic activity.

Изучена ультраструктура галоалкалофильной эндоэвапоритовой цианобактерии ‘Еuhalothece natronophila Z-M001 из содового озера Магади на начальных стадиях фоссилизации в модельной экспериментальной системе, предусматривающей культивирование в концентрированном карбонатном рассоле при внесении хлористого кальция. Показано, что образующийся в этих условиях аморфный CaCO3 может взаимодействовать с клеточной оболочкой на первых этапах кальцификации ‘Е. natronophila. Получены данные, свидетельствующие о том, что поверхностный слой оболочки ‘Е. natronophila, предположительно включающий полисахаридные и/или (глико)протеиновые компоненты, может участвовать в адсорбции и дальнейшей кристаллизации CaCO3 с образованием массивной “скорлупы”, в которую заключаются морфологически неизмененные клетки. Установлено, что в процессе минерализации CaCO3 изменяется ультраструктура клеточной стенки и внутритилакоидного пространства. На последующих этапах фоссилизации клетки, заключенные в кальцийсодержащую “скорлупу”, очевидно, мумифицируются и, в основном, сохраняют форму. По-другому происходит включение цианобактерий в глобулу троны. Оно сопровождается, по-видимому, прочным связыванием вещества растущего кристалла с элементами гликокаликса, заякоренными в наружную мембрану, что может приводить к ее отрыву от подлежащего слоя пептидогликана. Последний при этом сохраняется, а протопласты остаются сходными по ультраструктуре с интактными. Цианобактерии, инкорпорированные в крупные кристаллы троны, подвергаются деградации, деформируются и разрушаются. Этим можно объяснить, почему в массовых залежах троны озера Магади не обнаруживают фоссилий цианобактерий, которые в избытке находят в кальцийсодержащих слоях.

Phototroph communities were studied in Crimean highly mineralized sulphate-chloride lakes of marine and continental origin, and athalassic carbonate lakes of Altai Region. The diversity of communities providing primary production in mineral water bodies include: cyanobacterial biofilms and mats, algobacterial communities, plant-bacterial mats, cyanobacteria vegetating under mineral deposits, and planktonic communities. Morphology of the first three types is universal; it is similar to phototroph communities of other mineral lakes. Deviations from such structure may be caused both by physical and chemical parameters of environment, and the organism-ediphicator. In Crimean lakes all types of communities mentioned above were recorded, while in the Tantar system of reservoirs - only biofilms and one-year old mats. Biomass of the communities measured by chlorophyll а content, varied from 10 mg chl./m2 up to 600 mg chl./m2 depending on organisms-ediphicators. Species composition of dominating cyanobacteria in studied lakes depends on the level of mineralization of lake and presence of invertebrates with pasture type of feeding.

Transformation of clay minerals (smectite-zeolite, illite, kaolinite, and bentonite) and admixtures of iron oxides (hydroxides) under the action of an alkaline cyanobacterial community was studied. The results demonstrate that the processes of transformation of clay minerals such as intensification of removal of exchange bases and dissolution of silicates and iron oxides occurred in the presence of the alkaliphilic cyanobacterial community. The main factor that determines resistance of a mineral to biochemical weathering is its composition. Transformations of clay minerals in the course of active cyanobacterial photosynthesis (up to 14 days) and at decomposition of organic matter (OM) (28–60 days) are different. For smectite-zeolite and illite, these processes are dissolution of silicates and oxides (removal of Si and Fe) and removal of exchange bases (K), which were observed at both the of biomass production and OM destruction stages. For two other clays, the processes of neosynthesis are more typical: formation of carbonates (most probably siderite for bentonite clay and Mg-calcite for kaolin clay) and transformation of ferrihydrite into the more thermodynamically stable goethite.

This work studies the diversity of cyanobacterial and algal-bacterial communities of saline water bodies in the Crimean Peninsula and Altai Region. Plant-bacterial communities are described for the first time. The dependence of the production and destruction on the season and salinity of the water body is shown. The development of planktonic cyanobacteria is related to the presence of zooplankton, the development of which is controlled by hydrogen sulfide. The high hydrogen sulfide tolerance of benthic cyanobacteria secures the integrity of cyanobacterial communities. Observations in nature and laboratory modeling show that the formation of mineral layers is restricted to conditions of supersaturation with mineral components. Carbonate precipitation can take place in cyanobacterial communities under conditions of mixing sea water enriched with Ca and Mg with continental water enriched with sodium carbonate. Cyanobacteria are able to form and transform various Ca-Mg-carbonates. Dolomite formation is a derived process that occurs in cyanobacterial mats in the presence of sulfate-reducing bacteria. Carbonatization of cyanobacterial cells is considered using the example of the unicellular halophilic-alkaliphilic cyanobacterium Euhalothece sp. The accomplished study is of certain interest for interpretation of geological and paleontological data in the context of the supposed analogy between cyanobacterial mats and ancient stromatolites.

The aim of the study was to investigate the transformations of bentonite, illite, kaolin and smectite–zeolite clay at the laboratory experiments under the growth and fossilization of alkaline cyanobacteria Microcoleus Chthonoplastes. Cyanobacteria influenced the chemical properties of studied clays. It had no visible influence on the mineralogy of bentonite and kaolin. Whereas the development of more smectitic layers within the illite matrices in case of illite clay and defect ‘island’ layer in the interlayer space of montmorillonite in smectite–zeolite clay were found. Cyanobacteria affected the properties of iron compounds, which are present in all studied clays as impurities. Both dissolution and precipitation processes of iron compounds were observed. In the experiments with smectite–zeolite and kaolin an increase in magnetic susceptibility and magnetization values connected with the precipitation of Fe in the form of metastable ferrihydrite followed by the formation of goethite were found. This process correlated with the mineralization of organic matter, which plays the role of inhibitor and prevents goethite crystallization during the growth of cyanobacteria. In the case of bentonite a decrease in both magnetic susceptibility and magnetization values connected with oxidation of Fe2+ in the magnetite (maghemite) structure and precipitation of goethite took place. Ferrihydrite is a key mineral in the biogenic cycle of Fe.

Strain Z-M001 of a unicellular cyanobacterium, assigned by analysis of the 16S rRNA gene sequence to the phylogenetic group of the generic level Euhalothece, was isolated from soda Lake Magadi. It was shown that strain Z-M001, unlike all other known cultured and uncultured organisms of the Euhalothece group, is extremely natronophilic, and it was named accordingly "Euhalothece natronophila". In its ecophysiological characteristics, it is comparable to extremely alkaliphilic organotrophic natronobacteria, which is essential for soda ecosystems, because cyanobacteria belong to primary producers. "E. natronophila" exhibits considerable morphological variability depending on the concentration of carbonates in the medium. The polymorphism of "E. natronophila" is primarily connected to limitation by utilizable forms of carbon.