Impact of nitrogen and drought on phycobiliprotein content in terrestrial cyanobacterial strains

Cyanobacteria are highly adaptable microorganisms, characterized by an ability to survive in different environments with unfavorable conditions. In order to determine the content and composition of phycobiliproteins in cyanobacterial strains, depending on environmental factors, such as drought, darkness, and lack of nutrients in the substrate, the quantity of these pigments was investigated in 21 cyanobacterial strains. The study was conducted with terrestrial, filamentous, N₂-fixing cyanobacterial strains, which belong to Nostoc and Anabaena genera, isolated from different soil types in the Vojvodina region (Serbia). All strains were cultivated in nitrogen-free medium, medium with nitrate concentration of 2 g?L^?1 in the presence of light, and in drought conditions (water activity less than 0.5 %), on inorganic substrate, in the dark. Statistically significant differences of phycocyanin and allophycocyanin contents were found in the case of strains cultivated in nitrogen-free medium compared to strains grown in the medium containing nitrogen. There were no statistically significant differences in phycoerythrin and total phycobilin contents between strains grown in media with and without nitrogen. The results suggest that nitrogen availability affects composition of phycobiliproteins in the tested strains without affecting the total phycobiliprotein content, which implies maintenance of balanced pigment abundance as cyanobacterial response to nitrogen source. Significantly lower concentrations of the studied pigments, which varied from 0.8 to 16.9 μg mg^?1 dry weight, were detected in strains exposed to dry and dark conditions. These data indicate the presence of preserved phycobiliproteins after a period of 10 years of cyanobacterial exposure to drought and darkness, which can be of great importance for the study on their stability under unfavorable environmental conditions.     

The embryonic and post-embryonic development in two Drosophila species exposed to the static magnetic field of 60 mT

In this study, a static magnetic field influence on development and viability in two different species, Drosophila melanogaster and Drosophila hydei, was investigated. Both species completed development (egg-adult), in and out of the static magnetic field induced by double horseshoe magnet. Treated vials with eggs were placed in the gap between magnetic poles (47 mm) and exposed to the average magnetic induction of 60 mT, while control ones were kept far enough from magnetic field source. We found that exposure to the static magnetic field reduced development time in both species, but statistical significance was found only for D. hydei. Furthermore, we found that the average viability of both Drosophila species exposed to the magnetic field was significantly weaker compared to control ones. These results indicate that 60 mT static magnetic field could be considered as a potential stressor, influencing on different levels the embryonic and post-embryonic development of individuals.     

Agonistic autoantibodies directed against the angiotensin II AT1 receptor in patients with preeclampsia

We showed that sera from patients with preeclampsia contain autoantibodies directed against the angiotensin II AT1 receptor. The antibodies recognize an epitope on the second extracellular loop of the receptor and are immunoglobulins of the IgG3 subclass. The antibodies accelerate the beating rate of neonatal rat cardiomyocytes. The agonistic effect can be blocked with the AT1 receptor blocker losartan and can be neutralized by a peptide corresponding to the AT1 receptor's second extracellular loop. In further studies we shown that the autoantibodies recognize a specific conformation of the AT1 receptor. Cleavage of the external disulfide bond with dithiothreitol caused an inactivation of the receptor when stimulated either with Ang II or the autoantibodies in a system of cultured neonatal rat cardiomyocytes. Long-term stimulation of the AT1 receptor with either agonists down-regulated the AT1 receptor-mediated response to a second Ang II stimulation. These observations show that the agonistic autoantibodies behave pharmacologically in a similar fashion to Ang II. We have found the autoantibodies in all women meeting the clinical criteria of preeclampsia and suggest that they may be important to the pathogenesis of the disease.     

Antioxidant activity and phenolic profile in filamentous cyanobacteria: the impact of nitrogen

In the present study, ethanolic extracts of ten cyanobacterial strains cultivated under different nitrogen conditions were assessed for the phenolic content and antioxidant activity. The amount of detected phenolic compounds ranged from 14.86 to 701.69 μg g^?1 dry weight (dw) and HPLC-MS/MS analysis revealed gallic acid, chlorogenic acid, quinic acid, catechin, epicatechin, kaempferol, rutin and apiin. Only catechin, among the detected phenolics, was present in all the tested strains, while quinic acid was the most dominant compound in all the tested Nostoc strains. The results also indicated the possibility of increasing the phenolic content in cyanobacterial biomass by manipulating nitrogen conditions, such as in the case of quinic acid in Nostoc 2S7B from 70.83 to 594.43 μg g^?1 dw. The highest radical scavenging activity in DPPH assay expressed Nostoc LC1B with IC₅₀ value of 0.04?±?0.01 mg mL^?1, while Nostoc 2S3B with IC₅₀ =?9.47?±?3.61 mg mL^?1 was the least potent. Furthermore, the reducing power determined by FRAP assay ranged from 8.36?±?0.08 to 21.01?±?1.66 mg AAE g^?1, and it was significantly different among the tested genera. The Arthrospira strains exhibited the highest activity, which in the case of Arthrospira S1 was approximately twofold higher in comparison to those in nitrogen-fixing strains. In addition to this, statistical analysis has indicated that detected phenolics were not major contributor to antioxidant capacities of tested cyanobacteria. However, this study highlights cyanobacteria of the genera Nostoc, Anabaena, and Arthrospira as producers of antioxidants and phenolics with pharmacological and health-beneficial effects, i.e., quinic acid and catechin in particular.     

Increased motor activity of the beetle Laemostenus punctatus caused by a static magnetic field of 110 mT

The aim of this study was to investigate the effects of a static magnetic field on six behavioral parameters (travel distance, average speed while in motion, travel distance of the head, body rotations, time in movement, and immobility time) of the ground beetle Laemostenus (Pristonychus) punctatus (Dejean) (Coleoptera: Carabidae). Adults of this troglophilic and guanophilic beetle were randomly divided into two groups, the first exposed to a static magnetic field of 110 mT for 5 h, and the second a control group. Beetle behavior after these 5 h was monitored in an open‐field test for 12 min and analyzed using ANY‐maze software. Exposure to a static magnetic field of 110 mT increased motor activity (travel distance and average speed while in motion) in the first 4 min. After that there were no significant differences. We conclude that the applied static magnetic field affects motor activity of adult specimens of L. (P.) punctatus, and we discuss the mechanism, possibly through acting on the control centers responsible for orientation and movement.     

Target identification by chromatographic co-elution: monitoring of drug-protein interactions without immobilization or chemical derivatization

Bioactive molecules typically mediate their biological effects through direct physical association with one or more cellular proteins. The detection of drug-target interactions is therefore essential for the characterization of compound mechanism of action and off-target effects, but generic label-free approaches for detecting binding events in biological mixtures have remained elusive. Here, we report a method termed target identification by chromatographic co-elution (TICC) for routinely monitoring the interaction of drugs with cellular proteins under nearly physiological conditions in vitro based on simple liquid chromatographic separations of cell-free lysates. Correlative proteomic analysis of drug-bound protein fractions by shotgun sequencing is then performed to identify candidate target(s). The method is highly reproducible, does not require immobilization or derivatization of drug or protein, and is applicable to diverse natural products and synthetic compounds. The capability of TICC to detect known drug-protein target physical interactions (K(d) range: micromolar to nanomolar) is demonstrated both qualitatively and quantitatively. We subsequently used TICC to uncover the sterol biosynthetic enzyme Erg6p as a novel putative anti-fungal target. Furthermore, TICC identified Asc1 and Dak1, a core 40 S ribosomal protein that represses gene expression, and dihydroxyacetone kinase involved in stress adaptation, respectively, as novel yeast targets of a dopamine receptor agonist.     

Metabolic quenching of <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis>: efficiency of methods and impact of cold shock

Representative and valid cytoplasmic concentrations are essential for ensuring the significance of results in the field of metabolome analysis. One of the most crucial points in this respect is the sampling itself. A rapid and sudden stopping of the metabolism on a timescale that is much faster than the conversion rates of investigated metabolites is worthwhile. This can be achieved by applying of cold methanol quenching combined with reproducible, fast, and automated sampling. Unfortunately, quenching the metabolism by a sharp temperature shift leads to what is known as cold shock or the cell-leakage effect. In the present work, we applied a microstructure heat exchanger to analyze the cold shock effect using Corynebacterium glutamicum as a model microorganism. Using this apparatus together with a silicon pipe, it was possible to assay the leakage effect on a timescale starting at 1 s after cooling cell suspension. The high turnover rates not only require a rapid quenching technique, but also the correct application. Moreover, we succeeded in showing that even when the required appropriate setup of methanol quenching is not used, the metabolism is not stopped within the required timescale. By applying robust techniques like rapid sampling in combination with reproducible sample processing, we ensured fast and reliable metabolic inactivation during all steps.