Sodium transport in filamentous nitrogen fixing cyanobacteria

Two filamentous, nitrogen fixing cyanobacteria were examined for their salt tolerance and sodium (Na⁺) transport.Anabaena torulosa, a saline form, grew efficiently and fixed nitrogen even at 150 mM salt (NaCl) concentration while,Anabaena L-31, a fresh water cyanobacterium, failed to grow beyond 35 mM NaCl.Anabaena torulosa showed a rapidly saturating kinetics of Na⁺ transport with a high affinity for Na⁺ (K _m, 0.3 mM).Anabaena L-31 had a much lower affinity for Na⁺ (K_m, 2.8 mM) thanAnabaena torulosa and the pattern of uptake was somewhat different. BothAnabaena spp. exhibited an active Na⁺ extrusion which seems to be mediated by a Na⁺-K⁺ ATPase and aided by oxidative phosphorylation.Anabaena L-31 was found to retain much more intracellular Na⁺ thanAnabaena torulosa. The results suggest that the saline form tolerates high Na⁺ concentrations by curtailing its influx and also by an efficient Na⁺ extrusion, although these alone may not entirely account for its success in saline environment.     

氮磷营养盐对四种淡水丝状蓝藻生长的影响

通过设定不同的氮、磷营养盐浓度,在实验室条件下研究了不同浓度的氮和磷对4种淡水丝状蓝藻:皮质颤藻、尖细颤藻、蛇形颤藻和坑形细鞘丝藻生长的影响.结果表明,皮质颤藻和坑形细鞘丝藻对高浓度的氮、磷有着较强的适应能力,在硝态氮浓度0.016mg·mL^-1～2.0mg·mL、磷浓度1.36mg·mL^-1～13.6μg·mL时生长较好.4株藻在只存在氨态氮的情况下生长都受到抑制.     

The production of biomass and phycobiliprotein pigments in filamentous cyanobacteria: the impact of light and carbon sources

Cyanobacteria are recognized as producers of bioactive substances and phycobiliproteins, whose medicinal and functional food properties have led to increased interest in recent years. In the present study, the biomass production and phycobiliprotein content in cyanobacterial strains belonging to Anabaena, Nostoc and Spirulina genera were investigated under the conditions of continuous illumination and mixotrophic nutrition. The results showed that biomass production was strongly stimulated by continuous light in Spirulina strains (4.5-fold), and by organic carbon sources in N₂-fixing strains (2.1–2.8-fold). The strategy of cells to accumulate primarily blue pigment phycocyanin and bluish green allophycocyanin was revealed under tested conditions. Furthermore, in the case of Spirulina S1 grown with glycerol, the culture medium became dense and changed its colour to pink, which may indicate the release of compounds including pigment(s) outside the cell, the phenomenon that seem to be rare among cyanobacteria. Moreover, under continuous light, in this strain the highest biomass level of 4.0 mg/mL was achieved, wherein phycocyanin and allophycocyanin content was increased 12- and 16-fold, respectively, which indicates the high potential of this strain for further investigation.     

Cell-cell communication in filamentous cyanobacteria

Although cytoplasmic bridges between adjacent cells in the filaments of nitrogen-fixing cyanobacteria have been known for decades, the existence also of a continuous periplasm along the filaments raised the possibility that alternative modes of communication between cells could be utilized. The latter hypothesis was investigated by using GFP fusions to proteins whose expression is cell-specific and engineered to be transported into the periplasm. Two groups have recently obtained contradictory results, one supporting periplasmic transport of GFP from cell to cell, the other not. A third effort, involving members of the first group, used a smaller, soluble fluorophore and found rapid communication via the cytoplasmic bridges between cells. The dilemma of periplasmic diffusion remains unresolved.     

Antioxidant activity and phenolic content of the Indian wheat varieties

In this study, Indian wheat varieties grown under different agro-climatic zones were evaluated for their antioxidant potential. Different grain fractions (bran, flour, shorts) and the whole meal were tested using two free radicals (ABTS and DPPH) for their radical scavenging activities. More variation was observed in the antioxidant activities from different zones using DPPH assay. Irrespective of the method used, the whole meal and the bran of central zone varieties showed the highest and the north western plains zone varieties showed the lowest antioxidant activities. Within each growing zone, both the effect of genotype and environment was observed on the antioxidant activity. Both free and bound phenolic compounds were extracted from the bran of varieties representing different zones. Total phenolic content (TPC) varied from 2,900 to 5,650 μg Gallic acid equivalents/g of bran. Bound phenolic content was found to be more strongly correlated to the TPC than the free phenolic content. Highly significant genotypic differences were observed in the total phenolic content. This study therefore indicates that Indian wheat varieties have good antioxidant activity and high content of phenolic compounds and can be used further in breeding programmes to increase the content of phytochemicals responsible for antioxidant activity.     

Behavior of filamentous cyanobacteria in laboratory culture

The observations of a laboratory culture of filamentous cyanobacteria revealed a complex of behavioral responses of their community, which maintain their activity as an integrated entity. A number of structures formed in the course of filament regrouping were revealed and described; their possible structural and functional analogues in eukaryotic organisms were determined. It is assumed that the behavioral reactions of the filaments help to maintain the integrity of the community at the stage prior to the formation of the structural bonds between its elements.     

Morphogenesis in a community of filamentous cyanobacteria

Reversible differentiation was experimentally discovered in a community of modern filamentous cyanobacteria Oscillatoria terebriformis. Splitting of the initially uniform community into differentiated parts (strands, multiradiate aggregates, networks, etc.) occurs only for the duration of a function facilitating the activity of this community as an integral unit. The structures are formed as a result of regrouping of the filaments, without their specialization. A morphologically regulatory system (polygonal network) was found to develop under the impact of extreme factors. The levels of structural organization of filamentous cyanobacteria and multicellular eukaryotes were compared (individual cells in a filament—cell organelles; filaments—individual cells; community—organism), and the similarities and differences in morphogenesis of these groups were analyzed using the data on the embryonic regulation in multicellular eukaryotes. Spatial information in morphogenesis was shown to result not from direct realization of an inherited program but is created by the elements of integral organisms (cells and filaments) in the course of development.     

Behavior of filamentous cyanobacteria in laboratory culture

The observations of a laboratory culture of filamentous cyanobacteria revealed a complex of behavioral responses of their community, which maintain their activity as an integrated entity. A number of structures formed in the course of filament regrouping were revealed and described; their possible structural and functional analogues in eukaryotic organisms were determined. It is assumed that the behavioral reactions of the filaments help to maintain the integrity of the community at the stage prior to the formation of the structural bonds between its elements.     

Perforation patterns in the peptidoglycan wall of filamentous cyanobacteria

Ultrastructural studies were made on seven genera of filamentous cyanobacteria from Sections III and IV (in the Rippka classification): Oscillatoria limosa Ag. ex Gomont, Spirulina subsalsa Turp. ex Gomont, Crinalium epipsammum Crow, Nostoc commune Vaucher ex Born. et Flah., Anabaena variabilis Kützinger ex Born. et Flah., Arthrospira maxima Stizenb. ex Gomont, Arthrospira platensis Stizenb. ex Gomont, and Cyanospira rippkae Florenzano. Perforation types and their distribution in the peptidoglycan layer observed in Crinalium epipsammum Crow were similar to those in Oscillatoria limosa and two Arthrospira strains. In Cyanospira and Anabaena no junctional perforations in the peptidoglycan wall layer were observed; however, intracellular perforations were documented. Except for Spirulina , the perforations were organized in rows (up to 10) placed on both sides of the cross wall. In the Spirulina cross sections, perforations were found only in the thickened, inner part of the cell wall. The perforation patterns in Spirulina and Arthrospira strains were clearly different and justify the separation into different genera.     

Polyadenylated RNA in two filamentous cyanobacteria.

Polyadenylated RNA was detected in the cyanobacteria Nostoc sp. strain MAC and Anabaena variabilis by oligodeoxythymidylic acid-cellulose chromatography and by hybridization to [3H]polyuridylic acid. Polyadenylate tracts from A. variabilis were located at the 3' end of RNA chains and had an estimated length of 15 to 22 nucleotides.     

Propagation of electrical potential changes in filamentous cyanobacteria

Possible energy transmission along conjugating membranes was investigated. It was found by extracellular electrodes that under local illumination of blue-green algae Phormidium uncinatum the electrical current propagated along trichomes. The form and sign of the responses show that e. m. f. appears in the illumination region, which generates on the cellular membrane the potential difference with a negative charge inside the cell. The initiated transmembrane potential difference propagates along the filament of Ph, uncinatum like along a cable. The hypothesis concerning a cable structure of Ph, uncinatum was supported in the experiments with intersection of algae, and with intracellular injection of fluorescein showing the existence of direct diffusion exchange through cellular interfaces.     

Modification of the pII protein in response to carbon and nitrogen availability in filamentous heterocystous cyanobacteria

Abstract In the filamentous cyanobacterium Calothrix PCC 7504, which fixes N₂ aerobically, the modification state of the regulatory P_II protein (GlnB) was shown to depend on nitrogen and carbon availability, as observed in the unicellular non-fixing strain Synechococcus PCC 7942. However, the conditions for modifications, the time dependence of the process and the electrophoretic behavior of the native P_II isoforms differed somewhat between the two strains. In another strain, Calothrix PCC 7601, which has lost the capability to fix N₂, P_II was modified only if ammonia plus an inhibitor of glutamine synthetase were present. It is proposed that: (i) the behavior of the P_II proteins depends upon the physiological properties of the strains; and (ii) the modification system of P_II per se may differ between the two cyanobacterial genera.     

Antioxidant activity and phenolic profile of pistachio (Pistacia vera L., variety Bronte) seeds and skins

Pistachio (Pistacia vera L.; Anacardiaceae) is native of aride zones of Central and West Asia and distributed throughout the Mediterranean basin. In Italy, a pistachio cultivar of high quality is typical of Bronte (Sicily), an area around the Etna volcano, where the lava land and climate allow the production of a nut with intense green colour and aromatic taste, very appreciated in international markets. Pistachio nuts are a rich source of phenolic compounds, and have recently been ranked among the first 50 food products highest in antioxidant potential. Pistachio nuts are often used after removing the skin, which thus represents a significant by-product of pistachio industrial processing. The present study was carried out to better characterize the phenolic composition and the antioxidant activity of Bronte pistachios, with the particular aim to evaluate the differences between pistachio seeds and skins. The total content of phenolic compounds in pistachios was shown to be significantly higher in skins than in seeds. By HPLC analysis, gallic acid, catechin, eriodictyol-7-O-glucoside, naringenin-7-O-neohesperidoside, quercetin-3-O-rutinoside and eriodictyol were found both in pistachio seeds than in skins; furthermore, genistein-7-O-glucoside, genistein, daidzein and apigenin appeared to be present only in pistachio seeds, while epicatechin, quercetin, naringenin, luteolin, kaempferol, cyanidin-3-O-galactoside and cyanidin-3-O-glucoside are contained only in pistachio skins. The antioxidant activity of pistachio seeds and skins were determined by means of four different assays (DPPH assay, Folin-Ciocalteau colorimetric method and TEAC assay, SOD-mimetic assay). As expected on the basis of the chemical analyses, pistachio skins have shown to possess a better activity with respect to seeds in all tests. The excellent antioxidant activity of pistachio skins can be explained by its higher content of antioxidant phenolic compounds. By HPLC-TLC analysis, gallic acid, catechin, cyanidin-3-O-galactoside, eriodictyol-7-O-glucoside and epicatechin appeared to be responsible for the antioxidant activity of pistachio skin, together with other unidentified compounds. In conclusion, our work has contributed to clarify some particular characteristics of Bronte pistachios and the specific antioxidant power of pistachio skins. Introduction of pistachios in daily diet may be of undoubted utility to protect human health and well-being against cancer, inflammatory diseases, cardiovascular pathologies and, more generally, pathological conditions related to free radical overproduction. On the other hand, pistachio skins could be successfully employed in food, cosmetic and pharmaceutical industry.     

Survey of extrachromosomal DNA found in the filamentous cyanobacteria.

Cleared lysates of 13 species of filamentous cyanobacteria were examined for the presence of extrachromosomal DNA by using agarose gel electrophoresis and ethidium bromide staining. Seven of the 13 species contained extrachromosomal covalently closed circular DNA, and all but 1 species contained multiple elements. There was no correlation between the presence of extrachomosomal DNA and either the range of metabolic activities found in the cyanobacteria or the differentiated cell types or structures elaborated by the morphologically complex filamentous cyanobacteria.     

Membrane electrogenesis and sodium transport in filamentous nitrogen-fixing cyanobacteria

Transport of Na+ and its relationship with membrane potential (delta psi m) was examined in Anabaena L-31 (a fresh water cyanobacterium) and Anabaena torulosa (a brackish water cyanobacterium) which require Na+ for diazotrophic growth. The data on the effect of N,N'-dicyclohexylcarbodiimide indicated that delta psi m was generated by electrogenic proton extrusion predominantly mediated by ATPase(s). In addition, operation of a plasmalemmabound, non-ATP-requiring, H+-pumping terminal oxidase was suggested by the sensitivity of delta psi m to anaerobiosis, cyanide and azide, all of which inhibit aerobic respiration. The response of delta psi m to external pH and external Na+ or K+ concentrations indicated that a diffusion potential of Na+ or K+ may not contribute significantly to delta psi m. Kinetic studies showed that Na+ influx was unlikely to be a result of Na+/NA+ exchange but was a carrier-mediated secondary active transport insensitive to low concentrations (less than 10 mM) of external K+. There was a close correspondence between changes in delta psi m and Na+ influx; all the treatments which caused depolarisation (such as low temperature, dark, cyanide, azide, anaerobiosis, ATPase inhibitors) lowered Na+ influx whereas treatments which caused hyperpolarisation (such as 2,4-dinitrophenol, nigericin) enhanced Na+ influx. Remarkably low intracellular Na+ concentrations were maintained by these cyanobacteria by means of active efflux of the cation. The basic mechanism of Na+ transport in the fresh water and the brackish water cyanobacterium was similar but the latter demonstrated less influx, more efficient efflux, more affinity of carriers for Na+ and less accumulation of Na+, all attributes favouring salt tolerance.     

Antioxidant activity and metabolite profile of quercetin in vitamin-E-depleted rats

Dietary antioxidants interact in a dynamic fashion, including recycling and sparing one another, to decrease oxidative stress. Limited information is available regarding the interrelationships in vivo between quercetin and vitamin E. We investigated the antioxidant activity and metabolism of quercetin (Q) in 65 F-344 rats (n=13 per group) randomly assigned to the following vitamin E (VE)-replete and -deficient diets: (a) VE replete (30 mg alpha-tocopherol acetate/kg diet) control ad libitum (C-AL), (b) VE replete pair fed (C-PF), (c) VE replete+5.0 g Q/kg diet (R-VE+5Q), (d) VE deplete (<1 mg/kg total tocopherols)+5.0 g Q/kg diet (D-VE+5Q) and (e) D-VE. After 12 weeks, blood and tissue were collected for measurement of plasma vitamin E, quercetin and its metabolites, serum pyruvate kinase (PK), plasma protein carbonyls, malondialdehyde (MDA) and oxygen radical absorbance capacity. D-VE diets decreased serum alpha-tocopherol and increased PK activity in a time-dependent manner. The D-VE diet increased plasma protein carbonyls but did not affect MDA. Dietary quercetin supplementation increased quercetin and its metabolites in plasma and liver but did not affect D-VE-induced changes in plasma alpha-tocopherol, PK or protein carbonyls. Plasma isorhamnetin and its disposition in muscle were enhanced by the D-VE diet, as compared to the R-VE diet. Conversely, tamarixetin disposition in muscle was decreased by the D-VE diet. Thus, quercetin did not slow vitamin E decline in vivo; neither did it provide antioxidant activity in vitamin-E-depleted rats. However, vitamin E status appears to enhance the distribution of isorhamnetin into the circulation and its disposition in muscle.     

Miniprep DNA isolation from unicellular and filamentous cyanobacteria

A rapid miniprep method for isolation of DNA from 12 strains of cyanobacteria belonging to groups I, III, IV and V is described. The protocol is a modification of the methods of Boyle and Lew [Boyle, J.S., Lew, A.M., 1995. An inexpensive alternative to glassmilk for DNA purification. Trends Genet. 11, 8] and the cetyltrimethyl ammonium bromide (CTAB) extraction method of Sahgai-Maroof et al. [Sahgai-Maroof, M.A., Soliman, K.M., Jorgensen, R.A., Allard, R.W., 1984. Ribosomal DNA spacer-length polymorphisms in barley: Mendelian inheritance, chromosomal location and population dynamics. Proc. Natl. Acad. Sci. USA 81, 8014-80181. The new method is especially useful for obtaining cyanobacterial DNA from unicellular, filamentous and filamentous branched species. The method does not require phenol extraction and the product can be used directly for PCR amplification and restriction digestion.