Saturday, 15 July 2006

Role of Algobacterial Associations in Soil Forming Process.

Elena O. Omarova1, Galina M. Zenova1, Natalia P. Chizhikova2, and Vladimir K. Orleanskii3. (1) Moscow State Univ, Faculty of Soil Science, Vorob'evy gory, 119899, Moscow, Russia, (2) Dokuchaev Soil Science Institute, Pyzhevskii per. 7, 117019, Moscow, Russia, (3) Institute of Microbiology, Russian Academy of Sciences, pr. 60-letiya Oktyabrya 7, 117312, Moscow, Russia

Algobacterial associations with cyanobacteria are widespread in the places of primary soil formation and developed soils. The algobacterial associations in which actinomycetes formed dominating components of the prokaryotic complex were found in the places of primary soil formation on sedimentary rocks. The task was set in this work to study the biological aspects of coexistence of two groups of organisms, blue-green algae (cyanobacteria) and actinomycetes, and the changes in the lattices of kaoline components under the impact of growing algobacterial association. The objects of the investigation were represented by algologically pure cultures of alga (cyanobacterium) Oscillatoria terebriformis (Ag.) Elenk. emend., which were isolated from the natural algobacterial mat of Kamchatkan thermal spring, and a culture of actinomycetes Streptomyces odorifer, isolated from accumulating culture of cyanobacterium Oscillatoria terebriformis.The method was developed to study the interactions between the streptomycete and blue-green alga Oscillatoria terebriformis. The following parameters were used to judge the interaction between the cultures of the streptomycete and alga: (1) the presence of a positive tropism of the streptomycete to the alga; (2) stimulation of the algal growth in the associated culture with the streptomycete when the inoculate was placed on the surface and into clay minerals montmorillonite, kaolinite, and bentonite; (3) the occurrence of the streptomycete on the surface and in deep layers of the algobacterial mat constructed in the laboratory from the accumulating culture of O. terebriformis (Ag.) Elenk. emend. and streptomycete S. odorifer; (4) the increase of the photosynthetic activity of the alga in the associated culture with the streptomycete; and (5) the change of the antimicrobial properties of the associated culture in comparison with its components: streptomycete and alga. It was demonstrated that actinomycetes and blue-green algae (cyanobacteria) can coexist and mutually stimulate each other in the mixed culture. Analysis of changes in the lattices of kaoline components under the impact of growing algobacterial association consisting of blue-green alga Oscillatoria terebriformis and actinomycetes Streptomyces odorifer was carried out. The mineral phase was represented by kaolin (the clay deposit). The mineral composition of the kaolin was analyzed by x-ray diffractometry using a multipurpose Carl Zeiss Yena (Germany) XZC x-ray diffractometer. The initial kaolin sample consists of kaolinite (above 96 %) with an insignificant admixture of hydromicas, chlorite, and quartz. The identification of the kaolinite clay mineral is based on registering of reflections of d001 = 7.1485 and d002 = 3.5715 in the air-dry samples. The well-marked triplets at 4.4524, 4.3544, and 4.1613 fitting hkl 020, 110 and 111 in the specimens testify to the high degree of the kaolinite lattice perfection.The hydromyca is identified in the initial rock sample according to the reflections d001 = 10.0 , d002 = 4.9761 and d003 = 3.33 . The last hydromica reflection is overlapped by the quartz reflection d = 4.26 hkl 101. Both the mineralogical composition and crystallochemical structure of the kaoline changed after the cultivation of the algobacterial association for two months. The transformation of the prevailing kaolinite was registered by the altered intensities of the triplet at 4.4524, 4.3544, and 4.1613 . The reflection intensities were lower (though insignificantly) which, to some extent, pointed to a certain disorder in the lattice of the predominating mineral. The intensity of the hydromyca reflections decreased considerably. Three phases were identified: hydromyca (in the area of 10.0 ), residual chlorite (14.0 ) and a new formed swelling chlorite-smectite mixed-layered mineral ( about 19.0 ). These transformation of clay minerals, which were pronounced to a variable extent, are widespread in soils. The clay minerals in any rock (even such low-productive rocks as kaoline clay) undergo transformations under the influence of microorganisms over a shot period of time.

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