München, Techn. University, Diss., 2000.

Univ., Diss.--Regensburg, 1996.

Objetivo: Determinar la composición química y actividad antioxidante in vitro del extracto acuoso liofilizado de Nostoc sphaericum (Cushuro) de la laguna Cushurococha, Junín. Materiales y métodos: Estudio de enfoque cuantitativo; con diseño, descriptivo, observacional, transversal, la muestra biológica fue el extracto acuoso liofilizado de Nostoc sphaericum (Cushuro) que se recolectó de la laguna Cushurococha en el departamento de Junín. Se utilizaron los métodos Lowry, Antrona, Folin-Ciocalteu, el ensayo de captación de ABTS.+. Resultados: La cantidad, por muestra liofilizada, de proteínas solubles fue de 15.1mg/g, carbohidratos totales 949ug/g, polifenoles totales 2.98mg EAG/g; así también, el porcentaje de inhibición del radical ABTS.+ a una concentración de 0.15mg/mL de muestra liofilizada fue de 52%, un valor de IC50 entre 10-15 ug/mL y una capacidad antioxidante equivalente a trolox (TEAC-ABTS) igual a 0.384 ugEq. Trolox/ mg extracto de muestra seca. Conclusiones: El extracto acuoso liofilizado de Nostoc sphaericum constituye una buena fuente natural de antioxidantes.

Nostoc punctiforme is a nitrogen-fixing, symbiotic/free-living cyanobacterium. There has been a great deal of research conducted on the genomic nature of N. punctiforme as it pertains to its ecologically important role in the nitrogen cycle in varied environments around the world. My study concentrated on the dormant cell type known as the akinete. Increasing concentrations of NaCl were used to follow the growth phases from germination to akinete formation (lag phase-logarithmic growth phase-stationary phase). I found that increased salt concentrations caused N. punctiforme to form akinetes faster when compared to the control. Germination rates were not greatly increased or shortened by salt concentrations at or below 40 mM NaCl. Damage to cells due to NaCl was observed between 105 mM and 500 mM. Physiological studies, such as this one, enable better quantifiable field research since the organism’s limitations under laboratory conditions are known. This research allows researcher to more accurately plan and pick study sites, develop field studies and gives a solid basis for comparison to the natural environment.

Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 7 uppsatser.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 89-92). Also available via the Internet.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [135]-151).

The molecular biology of desiccation tolerance was investigated in the cyanobacteria with emphasis on Nostoc commune. Analysis of DNA from 41 samples of desiccated Nostoc spp. of varied age and global distribution led to the amplification of 43 independent tRNALEU(UAA) group 1 intron sequences. Phylogenetic analysis of the entire data set made it possible to define the form species Nostoc commune. The synthase (spsA) and phosphatase (sppA) genes required for the synthesis of sucrose were isolated from cyanobacterium Synechocystis sp. strain PCC 6803 and overexpressed in E. coli in two different vector constructions. Transformants had a marked increased capacity for desiccation tolerance. Sucrose synthesis was confirmed through thin layer chromatography (TLC) analysis of cell extracts from transformants. Long-term stability of DNA in desiccated Nostoc samples was demonstrated by the ability to amplify selected gene loci from samples stored dry for decades. Successful amplification in some samples was possible only after treatment with phenacylthiazolium bromide, a reagent that disrupts covalent cross-links; indicating that the DNA was modified by cross-links that occurred between reducing sugars and the primary amines on the DNA. Abundant superoxide dismutase was released following rehydration of desiccated field material N. commune CHEN after 13 years in the dry state. sodF mRNA was present in the dry material but was turned over within 15 min of rehydration. mRNA levels then rose and appeared to reach steady state levels after 3 hours and remained abundant after 24 hours of rehydration. / Master of Science

Filaments of the desiccation-tolerant cyanobacterium Nostoc commune are embedded within, and distributed throughout, a dense glycan sheath. Analysis of the glycan of field materials and of pure cultures of N. commune DRH1 through light and electron microscopy, immunogold-labelling and staining with dyes, revealed changes in the pattern of differentiation in glycan micro-structure, as well as localized shifts in pH, upon rehydration of desiccated field material. A Ca/Si rich external (pellicular) layer of the glycan acts as a physical barrier on the surface of N. commune colonies. A purified fraction (> 12 kDa) of an aqueous extract of the glycan from desiccated field material contained glucose, N -acetylglucosamine, glucosamine, mannose and galactosamine with ratios of 3.1 : 1.4 : 1 : 0.1 : 0.06, respectively. Ethanol extracts of N. commune contained trehalose and sucrose and the levels of both became undetectable following cell rehydration. Elemental analysis of glycan extracts showed a flux in the concentrations of salts in the glycan matrix following rehydration of desiccated colonies. Intracellular cyanobacterial trehalase was identified using immunoblotting and its synthesis was detected upon rehydration of desiccated field cultures. Water-stress proteins (Wsp; molecular masses of 33, 37, and 39 kDa are the most abundant proteins in glycan), a water soluble UV-AlB-absorbing pigment, the lipid-soluble UV-protective pigment scytonernim, as well as two unidentified cyanobacterial glycoproteins (75 kDa and 110 kDa), were found within the glycan matrix. No evidence was found for either glycosylation, phosphorylation or acylation of Wsp polypeptides. NH2-terminal sequence analysis of the three proteins of Wsp were identical: Ala-Leu-Tyr-Gly-Tyr-Thr-Ile-Gly-Glu-Gln-X-Ile-Gln- Asn-Pro-Ser-Asn-Pro-Ser-Asn-Gly-Lys-Gln. An unidentified 68-kDa protein, the second most abundant protein in aqueous extracts of the glycan, was isolated and its N-terminal sequenced was determined: Ala-Phe-lle-Phe-Gly-Thr-Ile-Ser-Pro-Asn-Asn-Leu-Ser-Gly- Thr-Ser-Gly-Asn-Ser-Gly-Ile-Val-Gly-Ser-Ala. Gene bank searches with these sequences, and an internal sequence ofWsp (Glu-Ala-Arg-Val-Thr-Gly-Pro-Thr-Thr-Pro-Ile-Asp), identified homologies with various carbohydrate-modifying enzymes. Purified Wsp polypeptides associate with 1,4-β-D-xylanxylanohydrolase activity that was inhibited specifically by Wsp antiserum. In the absence of salt, Wsp polypeptides, and the water-soluble UV -A/B-absorbing pigments, form multimeric complexes through strong ionic interactions. The role of the glycan, and the protein and pigments that reside within it, in the desiccation tolerance of N. commune is discussed with respect to structure/function relationships. / Ph. D.

The aim of the study was to investigate the morphology, ecology and phylogeny of cyanobacteria belonging to genera Nostoc and Desmonostoc in Lithuania. The detailed research of freshwater and terrestrial Nostoc and Desmonostoc species provided new data on taxonomy, biology and ecology of these cyanobacteria and the overall diversity of algae in Lithuania. 20 Nostoc species and two intraspecific taxa, and 18 taxa to the Nostoc genus level were identified. Twelve Nostoc species and intraspecific taxa, Desmonostoc genus including two taxa were recorded for the first time in Lithuania. A check list was compiled of all identified species with original morphological and ecological data as well as pictures. An applied research by different types of Nostoc and Desmonostoc species samples was valuable in morphological analysis – suitability for identification and stability of diagnostic morphological features in species was identified. The highest diversity of Nostoc and Desmonostoc species were recorded in lentic ecosystems and 14 species were found in terrestrial habitats. A wide genetic and morphological diversity of Nostoc and Desmonostoc species was identified while performing fingerprint TGGE and morphological analyses of cyanobacterial natural populations. The morphological and phylogenetic analyses of Nostoc and Desmonostoc strains showed morphological and phylogenetic heterogenity of Nostoc species and differences of the same types between Desmonostoc and Nostoc species. / Darbo tikslas – atlikti Lietuvos Nostoc ir Desmonostoc genčių melsvabakterių morfologijos, ekologijos ir filogenijos tyrimus. Pirmą kartą Lietuvoje atlikti išsamūs gėlųjų vandenų ir sausumos Nostoc ir Desmonostoc genčių melsvabakterių tyrimai papildo žinias apie dumblių rūšių įvairovę Lietuvoje bei suteikia naujos informacijos apie šių melsvabakterių taksonomiją, biologiją ir ekologiją. Identifikuota 22 Nostoc genties rūšys ir vidurūšiniai taksonai, 18 Nostoc taksonų identifikuota iki genties rango. Pirmą kartą Lietuvoje identifikuota 12 Nostoc genties rūšių ir vidurūšinių taksonų, dvi Desmonostoc genties rūšys. Rūšių konspekte pateikiami originalūs rūšių aprašymai su nuotraukomis ir ekologijos duomenys. Nostoc ir Desmonostoc genčių rūšių morfologinėje analizėje taikytas skirtingo tipo pavyzdžių tyrimas pasitvirtino – įvertintas rūšių diagnostinių morfologinių požymių stabilumas ir identifikacinis tinkamumas. Didžiausia Nostoc ir Desmonostoc genčių rūšių įvairovė identifikuota lentinėse ekosistemose, o sausumos buveinėse konstatuota 14 rūšių. Melsvabakterių gamtinių populiacijų molekulinių žymenų TGGE ir morfologinės analizių metu nustatyta gana didelė Nostoc ir Desmonostoc genčių rūšių genetinė ir morfologinė įvairovė. Nostoc ir Desmonostoc genčių padermių morfologinė ir filogenetinė analizės atskleidė Nostoc genties rūšių morfologinį ir filogenetinį heterogeniškumą bei Desmonostoc ir Nostoc genčių rūšių tokių tipų tarpusavio skirtumus.