Diversity of Chrysophycean Stomatocysts in the Steppe Zone of the South Urals.

Diversity of chrysophycean stomatocysts was studied in the steppe zone of the South Urals. A total of 14 stomatocyst morphotypes were identified, of which four were for the first time observed in Russia. Two morphotypes were described as novel. Morphological descriptions, scanning electron microscopic (SEM) images, and geographical locations were provided for all stomatocysts. High diversity of chrysophycean stomatocysts points to significant development of the chrysophyte flora in reservoirs of the steppe zone of the South Urals, making further research relevant.

[Antagonistic activity of novel green microalgae strain].

AIM: Screening of novel microalgae strains for the presence of pronounced antagonistic (antibacterial) activity against opportunistic bacteria. MATERIALS AND METHODS: 11 pure cultures of green unicellular algae isolated from fresh and salt basins of Orenburg region were studied for the presence of antagonistic activity against 4 test-strains of opportunistic bacteria by a photometric method. The effect of water extracts of microalgae Astermonas gracilis on the speed of self-purification of brine from Escherichia coli as well as antibacterial activity of peloid were evaluated under co-cultivation conditions. RESULTS: Pure cultures of green unicellular algae Scenedesmus obliquus (Turpin) Kütz, Scenedesmus magnus Meyen var. magnus, Pediastru duplex Meyen var. duplex, Chlorella vulgaris Bory, Monoraphidium arcuatum (Korschikov) Hindak (=Ankistrodesmus arcuatus Korschikov), Dictyosphaerium sp. had the most pronounced antagonistic activit against opportunistic bacteria. Water extract ofA. gracilis microalgae accelerated brine self-purification fro E. coli due to antibacterial effect. Peloid containing extracts of microorganism cells had a pronounced antibacterial effect against opportunistic bacteria. CONCLUSION: Antagonistic substances localized inside cells of microalgae increased the speed of allochthonic microorganism elimination that is one of the mechanisms of self-purification of a basin and antibacterial effect of peloid. The novel green microalgae strains studied due to the presence of pronounced antagonistic activity may have a wide practical application.

[Regulation of symbiotic interactions in algobacterial associations].

AIM: To study mechanisms of survival and regulation of natural algobacterial associations. MATERIALS AND METHODS: Lysozyme, antilysozyme, catalase and antagonistic activity as well as hydrogen peroxide production were determined in algobacterial associations formed by green algae or cyanobacteria and satellite bacteria. For assessment of reactions of microbial interactions, derivates of Escherichia coli, which differ on the presence of antilysozyme and catalase signs, were used. RESULTS: Multidirectional effects of symbionts in biocenosis were revealed. Involvement of functional systems lysozyme-antilysozyme and hydrogen peroxide-catalase in regulation of associative interactions in algae-bacterial biocenosis was established. In conditions of antibacterial action of algae's hydrogen peroxide, catalase activity of associate bacteria provides survival of microorganisms in association with algae, whereas high level of catalase activity promotes domination of associate bacteria in algobacterial communities. Antagonistic activity allows the microalgae to suppress growth of undesirable microorganisms and regulate their number in algobacterial cenosis. CONCLUSION: Functional systems lysozyme-antilysozyme, hydrogen peroxide-catalase as well as antagonistic activity of symbionts form the basis for regulation of symbiotic interactions in associations of water microorganisms, which has ecological and sanitary-hygienic implications.