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Biomedical subjects

K A Nikitina

Publications and source records attributed to K A Nikitina.

At least 19 recordsLinked to original sources
PubMedDate not supplied

[Changes in the ultrastructures of Anacystis nidulans cells at different temperatures].

If the cells of the blue-green alga Anacystis nidulans are put in the unfavourable conditions, the pairs of photosynthetic membranes separate, vacuoles are formed within thylakoids, and degradation of the photosynthetic apparatus occurs the earlier the sooner photosynthetic electron transport stops functioning: after 7--9 days in the dark, after 7--10 days in the light at 5 degrees C, after 5--7 days at 45 degrees C. If the cells are incubated at 5 and 45 degrees C, they become longer and form rods upto 10--12 mcm in length; at 45 degrees C, degradation takes place and the cell contents separate. The stationary phase of growth in the optimal conditions at 37 degrees C takes more time and the cells are degraded only after 45 days. If the temperature is lowered to 20 degrees C in the light, the cells remain viable for a long time and are degraded only after 60 days. In these conditions, invaginations of photosynthetic lamellae appear in the living cells, and the activity of TTC reduction in the light remains high for a long period of time. The cell wall remains intact upon degradation in remains high for a long period of time. The cell wall remains intact upon degradation in all the variants. Pigments are not destroyed both at a high (45 degrees C) and low (5 degrees C) temperature longer in the dark than in the light; therefore, photodestruction is involved in degradation of the lamellar apparatus in the light. The order in which pigments decompose differs depending on the conditions: chlorophyll is the first to be destroyed at 5 degrees C, phycocyanin at 45 degrees C, chlorophyll and phycocyanin at 37 degrees C; the rate of degradation of all pigments is almost the same at 20 degrees C. Apparently, additional pigments play different role in the processes of degradation occurring in the light.

Cyanobacteria↗
PubMedDate not supplied

[Morphologic heterogeneity under different conditions of living and destruction in Anabaena variabilis cyanobacteria].

The proportion between various morphological forms of the cyanobacterium Anabaena variabilis was studied under different conditions of its growth and destruction. When the cells lost viability at the stationary phase of cultural growth under the optimal conditions of illumination (1500--2000 lx), in the dark or when nitrogen was deficient, the filaments became shorter (4 to 2.2 cells per filament on the average), the cells larger, 4.5x6 microns). Under the conditions of nitrogen deficiency, the content of phycocyanin sharply decreased as well as that of chlorophyll. "Aging" under the conditions of optimal illumination was accompanied with "weighting" of the cells at the prolonged stationary phase and a gradual decrease in the content of phycocyanin and chlorophyll. When the cells were exhausted in the dark, the content of protein, RNA and phycocyanin decreased while that of chlorphyll hardly changed for a considerably long period of time. The most versatile morphological heterogeneity, when the cells were rapidly destroyed under the conditions of high light intensity, was as follows: both larger and more spherical as well as smaller and longer than in the control cells was found and catenuate cells were detected. The colour of the culture was light-brown or blue. When grown in a medium containing aspartic acid, the culture consisted of long filaments (ca. 18 cells per fragment instead of 4 cells in the control).

Chlorophyll↗
PubMedDate not supplied

[Blooming and destruction of cyanobacteria in the drainage bassin of the hydrogen sulfide spring of Staraya Matsesty].

The growth of cyanobacteria belonging to the genera Oscillatoria and Anabaena (up to 2.1 x 10(7) filaments per 1 g of wet sample) was found in a water reservoir with a high content of sulfides (up to 9 mM) in Staraya Matsesta throughout the year. The spots of Oscillatoria are located in the spring in more illuminated areas as compared to Anabaena. In the spring, not only spots of actively growing cells were detected, but also accumulations of Oscillatoria cells being destroyed (blue spots). Water-bloom spots in which Oscillatoria prevailed can transform into the spots of Anabaena. The main accompanying forms in the spots of Anabaena are long thin filaments of the flexibacterial type while short rods are found in the spots where Oscillatoria predominates. Heterotrophic enteric bacteria (48 x 10(4) cells per 1 g), Bacillus, Pseudomonas, and coryneform bacteria were also detected. Green bacteria (Chlorobium) and nonsulfur purple bacteria (Rhodomicrobium) were present in small quantities (16 x 10(3) cells per 1 g) as well as sulfate-reducing bacteria (5--15 x 10(2) cells per 1 g) and thiobacilli (40--60 cells per 1 g). In the spring, stones were covered with pink spots of spherical motile purple bacteria and with yellow-green spots of filamentous green bacteria. The cyanobacteria from the spots are capable of oxygenated photosynthesis. Fixation of CO2 by them in situ is 0.08 mcg per 1 g of dry sample per hour or 0.06 mcg per 10(6) cells per hour, and is inhibited by 10(-5) M DCMU by 70%.

Cyanobacteria↗
PubMedDate not supplied

[Age-related changes in the ultrastructure of Anabaena variabilis cells].

The growth and death of the obligate phototrophic cyanobacterium Anabaena variabilis Kütz, strain Lefevre, were studied under stationary conditions in the light. Each growth stage can be characterized by physiological and ultrastructural peculiarities. The following changes have been found in the cells with aging: the rate of oxygen evolution decreases, the photosynthetic lamellae untwist and separate with the formation of intrathylakoid vacuoles, the number of inclusions increases. Irreversible vesiculation of the parachromatophore was observed during the death of the cells. Lysis of the cells was found to be different in the light and in the dark.

Cyanobacteria↗