RESUMO
For heterotrophic microorganisms (44 strains) isolated-from the surface film of Lake Baikal, iden- tification was carried out and their. physiological and biochemical characteristics were determined. Com- pared to the water column, diversity of cultured heterotrophs was low, indicating formation of stable micro- bial communities at the air-water interphase interface. Heterotrophic bacteria isolated from the surface mi- crolayer exhibited the enzymatic activity comparable to that for strains form other biofilm associations. Deinococcusfi6us strain NA202 'vas the most active component of the community, capable of utilization of the broadest spectrum of mono- and disaccharides,'sugars, and amino acids. This strain possessed the highest diversity of extracellular enzymes and was the most resistant to UV radiation. The physiological and bio- chemical properties of this strain may-be responsible for its adaptation to survival in extreme conditions of the surface microlayer. Our results improve our understanding of occurrence of UV-resistant strains in freshwater ecosystems.
Assuntos
Deinococcus/metabolismo , Processos Heterotróficos/fisiologia , Lagos/microbiologia , Consórcios Microbianos/fisiologia , Filogenia , RNA Ribossômico 16S/genética , Alphaproteobacteria/classificação , Alphaproteobacteria/genética , Alphaproteobacteria/isolamento & purificação , Alphaproteobacteria/efeitos da radiação , Aminoácidos/metabolismo , Bacteroidetes/classificação , Bacteroidetes/genética , Bacteroidetes/isolamento & purificação , Bacteroidetes/efeitos da radiação , Betaproteobacteria/classificação , Betaproteobacteria/genética , Betaproteobacteria/isolamento & purificação , Betaproteobacteria/efeitos da radiação , Biodiversidade , Deinococcus/classificação , Deinococcus/isolamento & purificação , Deinococcus/efeitos da radiação , Deltaproteobacteria/classificação , Deltaproteobacteria/genética , Deltaproteobacteria/isolamento & purificação , Deltaproteobacteria/efeitos da radiação , Dissacarídeos/metabolismo , Ecossistema , Firmicutes/classificação , Firmicutes/genética , Firmicutes/isolamento & purificação , Firmicutes/efeitos da radiação , Gammaproteobacteria/classificação , Gammaproteobacteria/genética , Gammaproteobacteria/isolamento & purificação , Gammaproteobacteria/efeitos da radiação , Processos Heterotróficos/efeitos da radiação , Consórcios Microbianos/efeitos da radiação , Monossacarídeos/metabolismo , Proteobactérias/classificação , Proteobactérias/genética , Proteobactérias/isolamento & purificação , Proteobactérias/efeitos da radiação , Sibéria , Propriedades de Superfície , Raios UltravioletaRESUMO
The survival rate of bacteria of the genera Pseudomonas and Enterococcus isolated from Baikal Lake, exposed to different concentration of calcium hypochlorite used as a main agent for drinking water disinfection, was studied. Experimental studies have shown that chlorination was imperfect as this method is not always effective against Enterococci.
Assuntos
Compostos de Cálcio/química , Desinfecção/métodos , Água Potável/normas , Enterococcus/efeitos dos fármacos , Lagos/microbiologia , Purificação da Água/métodos , Enterococcus/crescimento & desenvolvimento , Enterococcus/isolamento & purificação , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Federação Russa , Microbiologia da Água/normas , Qualidade da ÁguaRESUMO
Diatoms significantly differ from other groups of heterokont algae in the diversity of chloroplast forms, their number, and location in a cell and in the structure of pyrenoids. The information on the fine structure of chloroplast is recognized to be important for taxonomic and phylogenetic studies of diatoms. Six species of diatoms belonging to different classes have been examined using transmission electron microscopy. New data on the structure of chloroplast have been obtained and characteristics of pyrenoid ultrastructure of diatoms belonging to different phylogenetic clades have been specified. The results enlarge the data obtained earlier and specify a set of features of chloroplast ultrastructure for different phylogenetic clades of diatoms.
Assuntos
Cloroplastos/ultraestrutura , Diatomáceas/ultraestrutura , Diatomáceas/classificação , Água Doce/microbiologia , Microscopia Eletrônica de Transmissão , SibériaRESUMO
A diatom Synedra acus subsp. radians (Kütz.) Skabitsch. has been studied by transmission electron microscopy. Examination of ultrathin sections demonstrated that silica dissolution in ammonium fluoride pH 5 under mild conditions leaves the key ultrastructural elements intact. The ultrastructure and arrangement of the cell organelles was studied during ontogeny. Silicalemma-surrounded silica deposition vesicles (SDVs) with maturating daughter valves and forming girdle bands have been identified. This method of SDV visualization offers considerable advantages over the standard approach without silica dissolution.
