Immobilization of cyanobacteria and microalgae on polyethylenimine-based sorbents

Immobilization of phototrophic microogranisms: microalgae (MA) and cyanobacteria (CB) on polyethylenimine (PEI)-based sorbents was studied. For this purpose, 3 insoluble porous polymeric materials were synthesized by cross-linking of PEI with epichlorohydrine and immobilization of PEI on the surface of styrene–divinylbenzene copolymer. The sorbent on the basis of cross-linked PEI was also alkylated with hexadecyl bromide to achieve hydrophobicity of its surface. The analysis of kinetics and efficiency of immobilization assessed for the model MA and CB cultures revealed the significant difference in the sorption activity of different types of sorbents depending on their synthesis procedure, chemical composition and hydrophilic-hydrophobic properties of polymeric surface. The hydrophobic sorbent obtained by immobilization of PEI on the surface of styrene–divinylbenzene copolymer characterized by very low sorption activity towards CB and MA cells. The highest immobilization efficiency of phototrophic cells was achieved for the hydrophilic sorbent on the basis of PEI cross-linked with epichlorohydrine, which provided the attachment of 50–70% of cells during 3 h of incubation. The hydrophobic sorbent based on alkylated cross-linked PEI effectively immobilized CB cells, while the colonization of the polymer surface by MA cells was very scarce. The noticed effect is explained by difference in prokaryotic (CB) and eukaryotic (MA) types of surface structures organization. Assessment of photosynthetic activity of immobilized MA cells by pulse-modulated fluorometry showed that hydrophobic sorbents had no toxic effect on the cells, while toxicity of hydrophilic cross-linked PEI-based sorbent was observed only after long-term cultivation ofphototrophic cells with this sorbent.     

Heterocysts with Reduced Cell Walls in Populations of Cycad Cyanobionts

The ultrastructure of the cyanobionts of the greenhouse-grown cycads Cycas circinalis, Ceratozamia mexicana, and Encephalartos villosus was studied. In addition to heterocysts with the typical ultrastructure, the cyanobiont microcolonies also contained altered heterocysts with reduced cell walls, which might dominate in all regions of the coralloid roots. The altered heterocysts represented a protoplast enclosed in a heterocyst-specific envelope with additional layers. Some heterocysts contained an additional reticular protoplast-enclosing sheath below the heterocyst-specific envelope, whereas the other heterocysts contained an additional electron-opaque outer layer. The substance of the inner sheath of the former heterocysts resembled the polysaccharides of mucilage, which fills the intercellular space, whereas the electron-opaque outer layer of the latter heterocysts probably had a protein nature. The substances that constitute the sheath and the outer layer are likely to be synthesized intracellularly and then released with the aid of membrane-bounded vesicles or by ruptures in the cytoplasmic membrane.     

Immobilization of bacteria on polymer matrices for degradation of crude oil and oil products

Organic polymer materials (OPM) differing in sets of functional groups, fiber surface thickness and character, and density of fiber packing in fabric were synthesized. OPM were studied for assessing the possibility of their application as sorbents for oil spills in water bodies. The synthesized OPM were used for the creation of bio-hybrid materials as matrices for immobilization of bacteria of the genus Rhodococcus sp. capable of petroleum degradation. Actively dividing bacterial cells forming clusters were shown to be present at the surface of fibers. Active attachment of the cells to polymeric surface due to intrusion and/or excretion of extracellular biopolymeric matrix were detected. The modification of polymer sorbents was shown to influence bacterial immobilization. The peculiarity of growth and the specificity of cell morphology of bacterial culture were noted.     

Dichroic ratio as the characteristic of the functional condition of the system

The principal deviation between parameters of spectral characteristics of surface structures and whole cells of unicellular algae Dunaliella tertiolecta and Tetraselmis viridis before and after influence of electromagnetic field (EMF) has been determined. It was found that the dichroic ratio can characterize the degree of adaptation of the culture to changing conditions of the environment.     

Methodology for determination of the state of microbial culture by degree of spatial organization of whole cells and their external structures

The proposed methodology for determination of biosystems state is based on registration of changes in the space-time parameters of cells and their external structures in a population of microorganisms from different taxonomic groups by the method of noninvasive layer-by-layer analysis using internal reflection spectroscopy. The dependence between the state of an organism and the changes in spatial organization of whole cells and their surface layers have been revealed. The proposed method allows estimation of the character and degree of dynamics of biosystem variations irrespective of the kind of influence. This method can be used for assessing the state of other organisms by the differences between values A for the surface structures and cells of these organisms.     

Dialysis cultivation of microorganisms as the appropriate model of population control in ecosystem research

Opportunities for application of methods of ecological control of anthropogenic impact on ecosystems have been considered. The biotic approach based on dialysis cultivation of microorganism populations has been suggested in order to evaluate the ecological state of living systems. Dialysis cultures are characterized with a high level of biomass accumulation and considerable extension of exponential and stationary growth phases. The cell state at dialysis cultivation corresponds to the state of the organisms in native nature conditions. The method for analysis of responses from microbe cells on external factors’ influence has been suggested. The method is based on the registration of alterations of time-spatial parameters in cell populations by layer-by-ayer noninvasive analysis using the spectroscopy of internal reflection.