Russian Journal of Biological Research

Number 2 (8), 2016

48-68
Studying the Process of Formation of Precambrian Period Limestone Fossils of Stromatolites in Hot Mineral Water Interacting with Caco3

Authors: Ignat Ignatov, Oleg Mosin

Abstract

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We studied the conditions of formations of stromatolites in hot mineral water. Studying these formations are very important and interesting as stromatolites store information about nascent life on earth and organic part of the first living organisms - numerous colonies of cyanobacteria, blue-green algae and bacteria, encountered in strata of limestone and dolomite in the crater of extinct volcanoes and thermal sources. For this aim were performed experiments with hot mineral and seawater from Bulgaria using IR and DNES spectroscopy. There were discussed the reactions of condensation and dehydration occurring in alkaline aqueous solutions at 65–95 0C and рН = 9–10, resulting in synthesis from separate molecules larger organic molecules as polymers and short polipeptides. It was shown that hot alkaline mineral water with temperature from +65 0C to +95 0C and pH value from 9 to 11 is more suitable for the origination of life and living matter than other analyzed water samples. The pH value of seawater on contrary is limited to the range of 7,5 to 8,4 units. In hot mineral waters the local maximums in IR spectra are more manifested compared to the local maximums obtained in IR-spectra of the same water at a lower temperature. The difference in the local maximums from +20 0C to +95 0C at each +5 0C according to Student t-criterion – p < 0,05. These data indicate that the origination of first organic forms of life depends on the structure and physical chemical properties of water, as well as its temperature and pH value. Also it was demonstrated the role of limestone and silica in the formation of the first organic life forms.

69-79
Optimization of Process Parameters for Effective Bioremediation of Chromium Contaminated Soil by Trichoderma Pseudokoningii

Authors: Rina Rani Ray, Debpali Sur

Abstract

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Release of hexavalent chromium in environment is usually the outcome of anthropogenic activities. Apart from its carcinogenicity, hexavalent chromium also contributes damage to the gastrointestinal, respiratory, reproductive and immunological systems. Hence removal of this toxic metal is very essential for the safety of both humans and animals. Microbial bioreduction of Cr (VI) to less toxic Cr (III) has proved to be an ecological and economical option for chromate detoxification. In this paper, we report the conversion of hexavalent chromium by the chromium reducing fungal strain of Trichoderma pseudokoningii, isolated from tannery effluent enriched soil near Kolkata. The study reveals that the isolated strain could grow well at a concentration of 1000 mg/L chromium, but spore formation became scanty as the concentration increased. Removal of hexavalent chromium was found to be accomplished through bio reduction rather than biosorption or bioaccumulation since no membrane bound and intracellular fraction bound Cr (VI) could be traced. Extra cellular chromium reduction was found to be highest when the culture medium (pH = 7) was supplemented with 0.5 % (w/v) pure dextrose and 0.09 % peptone as sole carbon and nitrogen source respectively. Reduction of potassium dichromate Cr (VI) at a concentration of 220 mg/L was highest after 144 hours of inoculation, i.e. at the stationary phase of growth of the strain. The reduction rate was enhanced in presence of cystine and DTT which might be due to the increased rate of activity of chromium reductase enzyme having thiol groups at its active site. Addition of acid treated human hair and feather in the culture medium boosted the power of chromate reduction by the strain. The gradual chromate reduction by the strain in soil kept in near natural conditions was confirmed by the data of atomic absorption spectroscopy which indicated the prospective role of the strain in successful bioremediation.