Growth and photosynthetic performance of Nostoc linckia (formerly N. calcicola) cells grown in BG11 and BG110 media.

The biotechnological potential of Nostoc linckia as a biofertilizer and source of bioactive compounds makes it important to study its growth physiology and productivity. Since nitrogen is a fundamental component of N. linckia biomass, we compared the growth and biochemical composition of cultures grown in BG11 (i.e., in the presence of nitrate) and BG110 (in the absence of nitrate). Cultures grown in BG11 accumulated more cell biomass reaching a dry weight of 1.65 ± 0.06 g L-1, compared to 0.92 ± 0.01 g L-1 in BG110 after 240 h of culture. Biomass productivity was higher in culture grown in BG11 medium (average 317 ± 38 mg L-1 day-1) compared to that attained in BG110 (average 262 ± 37 mg L-1 day-1). The chlorophyll content of cells grown in BG11 increased continuously up to (39.0 ± 1.3 mg L-1), while in BG110 it increased much more slowly (13.6 ± 0.8 mg L-1). Biomass grown in BG11 had higher protein and phycobilin contents. However, despite the differences in biochemical composition and pigment concentration, between BG11 and BG110 cultures, both their net photosynthetic rates and maximum quantum yields of the photosystem II resulted in similar.

New Nostocyclophanes from Nostoc linckia.

Six new nostocyclophanes and four known compounds have been isolated from Nostoc linckia (Nostocaceae) cyanobacterial strain UTEX B1932. The new compounds, nostocyclophanes E-J (1-6), were characterized by NMR and MS techniques. The known compounds were nostocyclophanes B-D, previously isolated from this strain, and dedichloronostocyclophane D. Structural modifications on the new [7.7]paracyclophane analogs 1-5, isolated from the 80% methanol fraction, range from simple changes such as the lack of methylation or halogenation to more unusual modifications such as those seen in nostocyclophane H (4), in which the exocyclic alkyl chains are of different length; this is the first time this modification has been observed in this family of natural products. In addition, nostocyclophane J (6) is a linear analog in which C-20 is chlorinated in preparation for the presumed enzymatic Friedel-Craft cyclization needed to form the final ring structure, analogous to the biosynthesis of the related cylindrocyclophanes. Nostocyclophane D, dedichloronostocyclophane D, and nostocyclophanes E-J demonstrated moderate to weak growth inhibition against MDA-MB-231 breast cancer cells.

Biochemical changes in cyanobacteria during the synthesis of silver nanoparticles.

The methods of synthesis of silver (Ag) nanoparticles by the cyanobacteria Spirulina platensis and Nostoc linckia were studied. A complex of biochemical, spectral, and analytical methods was used to characterize biomass and to assess changes in the main components of biomass (proteins, lipids, carbohydrates, and phycobilin) during nanoparticle formation. The size and shape of Ag nanoparticles in the biomass of both types of cyanobacteria were determined. Neutron activation analysis was used to study the accumulation dynamics of the Ag quantity. The analytical results suggest that the major reduction of Ag concentration in solutions and the increase in biomass occur within the first 24 h of experiments. While in this time interval minor changes in the N. linckia and S. platensis biomass took place, a significant reduction of the levels of proteins, carbohydrates, and phycobiliproteins in both cultures and of lipids in S. platensis was observed after 48 h. At the same time, the antiradical activity of the biomass decreased. The obtained results show the necessity of determining the optimal conditions of the interaction between the biomass and the solution containing Ag ions that would allow nanoparticle formation without biomass degradation at the time of Ag nanoparticle formation by the studied cyanobacteria.

Enhancement of active ingredients and biological activities of Nostoc linckia biomass cultivated under modified BG-110 medium composition.

The current work aims to investigate the effect of abiotic stresses (nitrogen (N) and sulfur (S) [0.0 g/l, 1.5 g/l, 3 g/l, 6 g/l, and 12 g/l N and 0.0 g/l, 0.07 g/l, 0.15 g/l, 0.3 g/l, and 0.6 g/l S] and their combination [0.3 g/l S + 6 g/l N]) of axenic culture of Nostoc linckia on the production of secondary metabolites which induce different biological activities. Growth rate was measured by dry weight (DW) and optical density (OD)550 nm. Additionally, phytochemical compounds, defense enzymes as well as antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(ethylbenzthiazoline-6-sulfonic acid) (ABTS·+) radical assays of crude extracts (methylene chloride:methanol, 1:1) were evaluated. Based on antioxidant activity, four promising extracts were subjected to different biological activities such as anticancer, antimicrobial, and antiviral activities. The obtained results revealed that supplementation of external nitrogen source in the form of sodium nitrate was found to increase the total phycobiliprotein content by fivefold. Also, nitrogen depletion provoked significantly highest quantities of phenolic and flavonoid content and this has effects on biological activities of Nostoc linckia. Moreover, 0.3 g/l S was found to be the most effective extract exhibiting a significant increase in antioxidant activity based on DPPH and ABTS assays, respectively (88.18 ± 0.64% and 84.20 ± 1.01%). Furthermore, it recorded anticancer activity against HCT 116 cell line with IC50 of 155 µg/ml. Moreover, this extract possessed a noticeable antibacterial potency (21.0 ± 1.0 as mm inhibition zone against Staphylococcus aureus and 19.3 ± 0.6 against Streptococcus mutans). In addition, its antiviral activity against H5N1 virus as a percentage of inhibition was 50% and 63.6% at a concentration of 7 µg/ml and 28 µg/ml, respectively, with cytotoxicity less than 7 µg/µl. GC-MS analysis recorded the presence of bioactive compounds exhibiting different biological activities. Therefore, the obtained results can represent valuable bioactive compounds with variable biological potencies.

Peculiarities of the Edaphic Cyanobacterium Nostoc linckia Culture Response and Heavy Metal Accumulation from Copper-Containing Multimetal Systems.

Soil and water pollution is a major problem that has a negative impact on ecosystems and human health in particular. In the bioremediation processes, the application of photosynthetic microorganisms, including cyanobacteria, is a direction of action addressed with increasing frequency in the context of further development and improvement of environmentally friendly techniques needed for detoxification of soils and waters polluted with low concentrations of toxic elements, since they pose a challenge for traditional treatment methods. In the present study, the removal of copper and other metal ions from multielement systems by three generations of Nostoc linckia is discussed. Changes in the biochemical composition of the nostoc biomass, which accumulates metal ions, were monitored. Neutron activation analysis was applied to assess Cu, Fe, Ni, and Zn accumulation by biomass, as well as to determine the biochemical composition of biomass after specific biochemical methods were used. The capacity of the accumulation of copper and other metal ions from multi-elemental systems by cyanobacteria Nostoc linckia was high and increased over two cycles of biomass growth in the systems Cu-Fe-Ni and Cu-Fe-Zn and over three cycles in Cu-Fe and Cu-Fe-Ni-Zn systems. It constituted 1720-10,600 µg metal/g depending on the system and cycle of cultivation. The accumulation of Fe, Ni, and Zn also increased over the generations of nostoc. The process of metal accumulation was demonstrated by a significant change in the biomass biochemical composition. Cyanobacteria Nostoc linckia possess a pronounced capacity of copper and other metal ion accumulation from multimetal systems and showed an increased resistance in environments polluted with heavy metals.