Algicidal characterization and mechanism of Bacillus licheniformis Sp34 against Microcystis aeruginosa in Dianchi Lake.

Microcystis aeruginosa blooms are a worldwide serious environmental problem and bloom control with bacteria is promising. In this study, a Bacillus licheniformis strain Sp34 with potent algicidal and inhibitory effects on the microcystins synthesis against fast-growing M. aeruginosa was isolated from Dianchi Lake. Sp34 killed the bloom-causing algal strain M. aeruginosa DCM4 of Dianchi Lake with an initial Chlorophyll-a concentration of 2.0 mg/L at a cell density of no less than 1.35 × 105 CFU/ml. It can also efficiently kill some other harmful algal species, such as M. wesenbergii and Phormidium sp. The algicidal activity of Sp34 relied on the release of algicidal substances, which had good heat (-20°C to 121°C) and acid-base (pH 3-11) resistance. In addition, the high algicidal activity depended on the good growth of algae indicated by the significantly positive correlations between algal growth and algicidal ratio (p < .001). The algicidal effect of Sp34 involved causing oxidative stress, lipid peroxidation, and morphological injury of algal cells, along with DNA damage and dysfunction of DNA-repair function, weakening the photosynthesis system, and inhibiting microcystin synthesis. In general, Sp34 can kill fast-growing M. aeruginosa and inhibit algal microcystin synthesis efficiently, so, it is a promising biocontrol agent to mitigate cyanobacterial blooms.

Interactive Effects of Melatonin and Nitrogen Improve Drought Tolerance of Maize Seedlings by Regulating Growth and Physiochemical Attributes.

Melatonin plays an important role in numerous vital life processes of animals and has recently captured the interests of plant biologists because of its potent role in plants. As well as its possible contribution to photoperiodic processes, melatonin is believed to act as a growth regulator and/or as a direct free radical scavenger/indirect antioxidant. However, identifying a precise concentration of melatonin with an optimum nitrogen level for a particular application method to improve plant growth requires identification and clarification. This work establishes inimitable findings by optimizing the application of melatonin with an optimum level of nitrogen, alleviating the detrimental effects of drought stress in maize seedlings. Maize seedlings were subjected to drought stress of 40-45% field capacity (FC) at the five-leaf stage, followed by a soil drenching of melatonin 100 µM and three nitrogen levels (200, 250, and 300 kg ha-1) to consider the changes in maize seedling growth. Our results showed that drought stress significantly inhibited the physiological and biochemical parameters of maize seedlings. However, the application of melatonin with nitrogen remarkably improved the plant growth attributes, chlorophyll pigments, fluorescence, and gas exchange parameters. Moreover, melatonin and nitrogen application profoundly reduced the reactive oxygen species (ROS) accumulation by increasing maize antioxidant and nitrogen metabolism enzyme activities under drought-stress conditions. It was concluded that the mitigating potential of 100 µM melatonin with an optimum level of nitrogen (250 kg N ha-1) improves the plant growth, photosynthetic efficiency, and enzymatic activity of maize seedling under drought-stress conditions.

Fine Particulate Matter Leads to Unfolded Protein Response and Shortened Lifespan by Inducing Oxidative Stress in C. elegans.

Oxidative stress has been proven as one of the most critical regulatory mechanisms involved in fine Particulate Matter- (PM2.5-) mediated toxicity. For a better understanding of the underlying mechanisms that enable oxidative stress to participate in PM2.5-induced toxic effects, the current study explored the effects of oxidative stress induced by PM2.5 on UPR and lifespan in C. elegans. The results implicated that PM2.5 exposure induced oxidative stress response, enhanced metabolic enzyme activity, activated UPR, and shortened the lifespan of C. elegans. Antioxidant N-acetylcysteine (NAC) could suppress the UPR through reducing the oxidative stress; both the antioxidant NAC and UPR inhibitor 4-phenylbutyric acid (4-PBA) could rescue the lifespan attenuation caused by PM2.5, indicating that the antioxidant and moderate proteostasis contribute to the homeostasis and adaptation to oxidative stress induced by PM2.5.

Cytotoxic constituents from the leaves of Broussonetia papyrifera.

AIM: To investigate the chemical constituents from the leaves of Broussonetia papyrifera. METHODS: The chemical constituents were isolated and purified by macroporous adsorptive resin D101, silica gel, and ODS column chromatography and preparative HPLC. Their structures were elucidated on the basis of 1D and 2D NMR analyses. In addition, their cytotoxic activity against human hepatoma carcinoma cells (HepG-2) were evaluated by the MTT method. Furthermore, RP-HPLC and colorimetric methods were used for the analysis of cosmosiin and total flavonoids. RESULTS: A new lignan, together with five known compounds were obtained, and their structures were characterized as (+)-pinoresinol-4'-O-ß-D-glucopyranosyl-4″-O-ß-D-apiofuranoside (1), cosmosiin (2), luteolin-7-O-ß-D-glucopyranoside (3), liriodendrin (4), 3, 5, 4'-trihydroxy-bibenzyl-3-O-ß-D-glucoside (5), and apigenin-6-C-ß-D-glucopyranside (6). Furthermore, RP-HPLC and colorimetric methods were established for the analysis of cosmosiin and total flavonoids. CONCLUSION: Compound 1 was a new lignan, and compounds 5 and 6 were isolated for the first time from the title plant. Compounds 1, 4 and 6 showed definite activities against HepG-2, while the other compounds didn't show inhibitory effects. The optimal harvest time of B. papyrifera (L.) Vent. is September.