Journal of Phycological Research
Volume:5 Issue: 1, Jun 2021

Antibacterial activities of MeOH and ‎aqueous extracts of Gracilaria salicornia (C. Agardh) Dawson, Padina boergesenii Allander and Kraft, Polycladia myrica (S. G. Gmelin) Draisma, were examined against Gram-positive bacteria ‎Staphylococcus aureus‏‎ Rosenbach 1884, Pseudomonas aeruginosa (Schröter 1872) Migula 1900, and Escherichia coli (Migula 1895). Indeed, extracts of wet samples showed 5.3±0.58 to 34.3±0.6 mm antibacterial activity. Furthermore, antioxidant activities of algae were evaluated using DPPH and ABTS radical scavenging methods. Whereas in the DPPH method, aqueous extract of Polycladia myrica showed the highest antioxidant activity, MeOH and aqueous extracts of Gracilaria salicornia exhibited the lowest antioxidant activity. Besides, the antioxidant activity of extracts was higher using the ABTS method. Additionally, aqueous extracts showed the lowest IC50 values in comparison to MeOH extracts. The total phenolic content of the aqueous extract was ‎5.07±0.08 to 46.73±0.24 mg gallic acid /100 g higher than the MeOH extract. The MeOH and aqueous extracts of Padina boergesenii demonstrated the highest TPC among others.

Cyanobacteria are oxygenic, photosynthetic prokaryotes with the unique potential to enhance plant growth, development, and productivity. These microorganisms have the ability to stimulate plant growth by producing growth-inducing phytohormones and increasing the solubility of soil nutrients. In the present study, the plant growth-promoting potential of Phormidium sp. on the growth indices of wild barley seedlings was evaluated. Phormidium sp. is a filamentous and non-heterocystous cyanobacterium. Filaments are unbranched and usually in fine, smooth, layered microscopic or macroscopic mats. The results showed that dry weight and length of root and shoot, the content of nitrogen (2%), potassium (2%), and auxin (8%) phytohormone of wild barley seedlings treated with Phormidium sp. had a significant increase compared to the control group. Accordingly, the use of Phormidium sp. as a plant growth-promoting cyanobacteria seems a promising alternative to chemical fertilizers.

Selenium (Se) is a necessary microelement for microalgae growth. Moreover, it might directly act and cause a decrease in primary production in microalgae. Nowadays, there is a great focus on preparations of Se-enriched products. In the current study, the effects of various selenate concentrations on Spirulina were evaluated as a primary stage to large-scale production of Se-enriched S. platensis. Zarrouk medium supplemented to investigate the stimulatory/inhibitory effects of selenate on growth at various concentrations. Biomass dry weight and cell mass were measured on OD550. Thereafter, inhibitory and algicidal concentrations were determined. Furthermore, its effects on morphology and changes of some important pigments in response to the metal challenge were investigated, too. While the results showed that at 5 and 10 ppm concentrations growth was supported, the dry weight of microalgae decreased at selenate levels above 50 ppm. Besides, the inhibitory and lethal effects of selenate were at 100 ppm and 300 ppm, respectively. In addition, morphological changes were observed at this concentration. Additionally, chlorophyll, carotenoid, and phycobiliproteins showed a stimulatory effect at 5-50 ppm, 10 ppm, and 10 ppm, respectively. Moreover, Spirulina uses for foods production because some chemicals are unique compounds. Simple cultivation method and high quality of its protein, and no toxic effects, cause its feasibility for large-scale production.

Seed priming has a significant effect on seed germination and improves the establishment of crops. In this study, rice seeds (Oryza sativa cv. Shiroodi L.) were primed by different concentrations (0, 0.025, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5 g/l) of Nostoc commune Vauch aqueous extract. Furthermore, seed germination rate, percentage, and seedling growth were examined. The results showed that N. commune extract had a significant positive effect on increasing the percent and rate of seed germination. Indeed, the length of roots and shoots in seedlings obtained from primed seeds with N. commune extract increased compared to those of the seedlings from primed seeds with water. Additionally, the highest seed germination percent and seedling length were obtained by 0.025 g/l N. commune extract. Based on the results, seed germination and seedling growth were not affected by seed priming with N. commune extract at concentrations of more than 0.1 g/l. Therefore, sowing rice seeds with a low concentration of N. commune extract can improve seed germination and seedling establishment.

Cyanobacteria produce a wide range of biologically active compounds. Among the cyanobacterial metabolites, cytotoxins are of particular interest because of their potential to kill target cancer cells. The present study was undertaken to isolate Nodularia harveyana from Ardakan County (Yazd Province, Iran) soil and determine the cytotoxic effect of cytoplasmic extract and medium culture of its on the human melanoma cell line. Nitrate-free BG11 medium was used for preparing an axenic monoalgal culture of Nodularia harveyana ISB112. In addition, 3- to 5-week-old cytoplasmic extraction and medium were used for the cytotoxic study on human melanoma cell lines (B16). The cytotoxic effects of cytoplasmic extract, and medium culture at the concentration ranging from 5 to 50 μg.ml-1 increased significantly in a concentration-dependent manner (p<0.05). The 4- and 5-week-old cytoplasmic extract of Nodularia harveyana ISB112 was more effective than the 3-week-old extract and the viability percent of cells were 52.57% and 52.35%, respectively. The results showed that the medium culture activity in the fifth week of growth was higher than other periods and the cell's viability percent was 48.84% (p ≤ 0.05). Overall, the results suggested that Nodularia harveyana ISB112 could kill tumor cells that can be used as a treatment for cancer disease.

Possibility of change in the phycobilisome status, photosynthetic pigments, photosynthetic ratios, and photosynthetic parameters of soil cyanobacteria Fischerella sp. FS 18 investigated. Neutral and extreme alkaline pH (7, 9), and short time incubation including 20, 40, and 60 minutes treatments. After purification, cyanobacteria were subjected to extreme alkaline treatment for one hour at 20, 40, and 60 minutes intervals. Colorimetric assays of phycocyanin, allophycocyanin, phycoerythrin, chlorophyll) and a comparison of the combined effect of time and alkalinity on photosynthetic ratio performed. Indeed, the photosynthesis-light curves compared with direct measurements. The results showed that the combined treatment of time and alkalinity after 20 minutes of inoculation significantly increased the performance of the photosystem and stability of the phycobilins. While, under the 40 min and both neutral and alkaline treatments, the yield of photosystem II, increased the production of the photosystem I, and significantly the linear fraction of the photosynthesis-light curve. Although, the needed energy to achieve maximum photosynthesis was reduced. Further, the maximum photosynthesis was completely different at 40 min pretreatment and without pretreatment. Furthermore, the results show no specific regularity and trend at 20 and 60 minutes of treatment. Thus, the production of light collecting-antennas is influenced by both time and alkalinity treatments. In consequence, 60 minutes or fewer treatment times, cause a significant change in the structure and performance of the photosynthetic apparatus. While alkaline treatments at a short time significantly save energy and enhance photosynthesis.