Involvement of optical methods for condition assessment of cyanobacteria cells under the action of TiO2

Abstract

Under optimal conditions, the division of unicellular cyanobacteria lasts 6-12 hours, so during the growing season there is an avalanche of reproduction. It also leads to increased exports of their metabolites to the environment. The toxins of Cyanobacterial after the destruction of these cells enter the aquatic environment and cause poisoning of aquatic organisms and animals and people who consume poisoned water. To avoid the release of toxins, it is necessary to control the rate of accumulation of cyanobacterial biomass. It is proposed to use titanium oxide (IV) as an adsorbent to regulate the number of cyanobacteria. TiO2 has a number of advantages: chemical and biological inertness, non-toxicity, high photostability. The aim of the work was to involve methods of microscopy of native and stained drugs to assess the physiological state of Microcystis pulverea (H.C. Wood) Forti under the action of TiO2. Microcystis pulverea was grown on Fitzgerald medium in the modification of Zender and Gorham №11, at a temperature of 21 ° C and a 16-hour photoperiod in a climatic room. To the cell biomass (4.5 x 106 cells / ml) was made white powder TIO2 in different concentrations: 0.5%, 1%, 2.5%, 5%. To assess the condition of M. pulverea cells after exposure to titanium (IV) oxide, microscopy of objects was performed. Native cells were analyzed for the presence of protective mu-cous formations. The localization of mucous formations on the surface of TiO2 was evaluated. Differential staining was used to determine the presence of living and dead cells and the number of metabolically active cells. These indicators make it possible to assess the condition of cyanobacterial cells under the influence of various environmental factors. To deter-mine the number of dead cells, the cells were stained with vital dyes (methylene blue and neutral red - 1: 5000). To determine the number of physiologically active cells and cytochrome oxidase test were performed according to standard methods. In both cases, cells were counted using a Fuchs-Rosenthal camera and a Micromed XS-3300 trinocular microscope. In samples with high concentrations of titanium dioxide, the cells remained unprotected. It is noted that the mucus was adsorbed around TIO2. The lowest degree of adsorption was characterized by samples containing 0.5% TiO2, and the highest degree - with 5% TiO2. When using TiO2, more than 2.5% can completely release cells of cyanobacteria in the aqueous medium from the mucous that protects their cells, and then use other drugs for lysis. An increase in the number of dead cells was observed in cyanobacterial culture. In M. pulverea culture, the number of metabolically active cells decreases sharply with increasing concentration of TiO2. Incubation with TiO2 led to a gradual decrease in the number of metabolically active cells: from 96% (in the control sample) to about 9% in the presence of 5% TiO2. Although this culture remains relatively alive, but loses the ability to actively metabolize. It can be predicted that over time the number of M. pulverea cells will decrease sharply, which will lead to the death of the culture as a whole.