Development,morphological characteristics and viability of temporary cysts of Pyrodinium bahamense var. compressum (Dinophyceae) in vitro

Pellicle or temporary cysts of Pyrodinium bahamense var. compressum (Böhm) Steidinger, Tester & F.J.R. Taylor and their role in bloom dynamics have not yet been adequately characterized and understood. We investigated the role of temperature- and nutrient-mediated stress as factors that could induce pellicle formation in batch cultures. Cellular features and their implications for temporary cyst viability were examined using confocal laser scanning microscopy (CLSM). Our data suggest that temperature change is one of the key factors influencing pellicle formation, preserving viability at low temperature (i.e. 13°C). Hypnocysts (resting cysts) were not observed. During pellicle formation, motile cells generally undergo ecdysis, extrusion of cytoplasmic materials and bacteria, compaction of the nucleus and non-motility. The outermost covering of the temporary cysts shows red autofluorescence and it contains lower concentrations of chlorophyll (chl) a and no detectable chl c. The nuclear region is surrounded by transitional red bodies and other unidentified cellular structures. Temporary cysts can immediately revert back to the motile state upon exposure to optimum conditions. This is accompanied by the expansion of the nuclear region, regeneration of the chloroplasts and enlargement of the cell. Developmental changes during reversal of temporary cysts to motile forms were also observed to cause breaks in the cell covering that could serve as sites for bacterial entry. Though observed in vitro, such behaviour may also be occurring in nature especially as a response to drastic short-lived environmental changes. This is the first detailed report on the characteristics of temporary cysts of P. bahamense var. compressum.     

Indirect shoot organogenesis from leaves of Dieffenbachia cv. Camouflage

A novel protocol for indirect shoot organogenesis of Dieffenbachia cv. Camouflage was established using leaf explants excised from in vitro shoot cultures. The frequency of callus formation reached 96% for explants cultured on Murashige and Skoog (1962) basal medium supplemented with 5 μM thidiazuron and 1 μM 2,4-dichlorophenozyacetic acid. The number of shoots regenerated was high, with up to 7.9 shoots produced per callus cultured on basal medium supplemented with 40 μM N ⁶-(Δ²-isopentenyl)adenine and 2 μM indole-3-acetic acid. Regenerated shoots rooted well in a soilless substrate, acclimatized ex vitro at 100%, and grew vigorously under shaded greenhouse conditions. Somaclonal variations in leaf variegation, color, and morphology have been observed in regenerated plants.     

The Pool of Chlorophyllous Pigments in Barley Seedlings of Different Ages under Heat Shock and Water Deficit

The effects of a high temperature (3 h, 40°C) and water deficit (45 h on 3% PEG 6000) on the pool of chlorophyllous pigments in the leaves of 4-, 7-, and 11-day-old barley (Hordeum vulgare L.) seedlings were studied. Heating resulted in a decrease in the total content of chlorophylls (Chl) (a + b) in 4-day-old plants but not in the older leaves. Water deficit induced an increase in the pigment content in young seedlings but reduced it in the leaves of 11-day-old plants. In young seedlings, hyperthermia and dehydration affected similarly Chl (a + b) degradation, leading to a marked inhibition of the chlorophyllase (Chlase) activity hydrolyzing Chl to chlorophyllides and phytol. In old leaves, an activation of this enzyme was observed. The stress factors under study affected different stages of pigment biosynthesis. High temperature inhibited the activity of dark and light stages of Chl(a + b) biosynthesis. Dehydration did not change markedly the resynthesis of protochlorophyllide, while the enzymes of the light stage of Chl biosynthesis were activated in young but inhibited in old barley leaves. The results thus obtained allowed us to conclude that heat treatment and dehydration specifically affected the Chl biosynthesis. At the same time, the Chlase response was nonspecific.     

Phosphogenesis in the 2460 and 2728 million‐year‐old banded iron formations as evidence for biological cycling of phosphate in the early biosphere

The banded iron formation deposited during the first 2 billion years of Earth's history holds the key to understanding the interplay between the geosphere and the early biosphere at large geological timescales. The earliest ore‐scale phosphorite depositions formed almost at ~2.0–2.2 billion years ago bear evidence for the earliest bloom of aerobic life. The cycling of nutrient phosphorus and how it constrained primary productivity in the anaerobic world of Archean–Palaeoproterozoic eons are still open questions. The controversy centers about whether the precipitation of ultrafine ferric oxyhydroxide due to the microbial Fe(II) oxidation in oceans earlier than 1.9 billion years substantially sequestrated phosphate, and whether this process significantly limited the primary productivity of the early biosphere. In this study, we report apatite radial flowers of a few micrometers in the 2728 million‐year‐old Abitibi banded iron formation and the 2460 million‐year‐old Kuruman banded iron formation and their similarities to those in the 535 million‐year‐old Lower Cambrian phosphorite. The lithology of the 535 Million‐year‐old phosphorite as a biosignature bears abundant biomarkers that reveal the possible similar biogeochemical cycling of phosphorus in the Later Archean and Palaeoproterozoic oceans. These apatite radial flowers represent the primary precipitation of phosphate derived from the phytoplankton blooms in the euphotic zones of Neoarchean and Palaoeproterozoic oceans. The unbiased distributions of the apatite radial flowers within sub‐millimeter bands do not support the idea of an Archean Crisis of Phosphate. This is the first report of the microbial mediated mineralization of phosphorus before the Great Oxidation Event when the whole biosphere was still dominated by anaerobic microorganisms.     

Surfactant-mediated amyloidogenesis behavior of stem bromelain; a biophysical insight

Neurodegenerative disorders are mainly associated with amyloid fibril formation of different proteins. Stem bromelain (SB), a cysteine protease, is known to exist as a molten globule state at pH 10.0. It passes through the identical surrounding (pH 10.0) in the gut epithelium of intestine upon oral administration. Protein–surfactant complexes are widely employed as drug carriers, so the nature of surfactant toward protein is of great interest. The present work describes the effect of cationic surfactants (CTAB & DTAB) and their hydrophobic behavior toward amyloidogenesis behavior of SB at pH 10.0. Multiple approaches including light scattering, far UV-CD, turbidity measurements, and dye binding assay (ThT, Congo red and ANS) were performed to measure the aggregation propensity of SB. Further, we monitored the hydrodynamic radii of aggregates formed using dynamic light scattering technique. Structure of fibrils was also visualized through fluorescence microscopy as well as TEM. At pH 10.0, low concentration of CTAB (0–200 μM) induced amyloid formation in SB as evident from a prominent increase in turbidity and light scattering, gain in β-sheet content, and enhanced ThT fluorescence intensity. However, further increase in CTAB concentration suppressed the fibrillation phenomenon. In contrast, DTAB did not induce fibril formation at any concentration used (0–500 μM) due to lower hydrophobicity. Net negative charge developed on protein at high pH (10.0) might have facilitated amyloid formation at low concentration of cationic surfactant (CTAB) due to electrostatic and hydrophobic interactions.     

Studies on the catalytic ability of palladium wire, foil and sponge in the Suzuki-Miyaura cross-coupling

Different forms of metallic palladium (wire, foil and sponge) have been tested as potential catalysts in the Suzuki-Miyaura cross-coupling. All samples showed to be catalytically active for both electron-poor and electron-rich aryl bromides combined with a variety of arylboronic acids. Palladium wire has been recycled six times without decrease of activity. A series of poisoning experiments demonstrated that the true catalyst is a soluble form of palladium arising from a leaching process. Interestingly, metal leaching from palladium foil has been clearly evidenced by SEM.     

Micropropagation of Drosera peltata,a Tuberous Sundew,by Shoot Tip Culture

In order to establish and optimize an in vitro micropropagation method of Drosera peltata (a tuberous sundew), a carnivorous plant, the effects of medium type, MS medium concentration, pH and cytokinin type on shoot proliferation and tuber formation were investigated, using one month-old shoot tips. The shoot proliferation and tuber formation were most effective on 1/2 MS medium without cytokinins. The optimum pH of the media was pH 5.7. Tubers were planted in plastic pots filled with 1:1 peat moss and sand. The survival rate of the plantlets was almost 100%, and they exhibited normal development. With subculture every 12 weeks, hundreds of the plants were propagated from a single plant within a year.     

Nonlinear stability analyses of vegetative pattern formation in an arid environment

The development of spontaneous stationary vegetative patterns in an arid isotropic homogeneous environment is investigated by means of various weakly nonlinear stability analyses applied to the appropriate governing equation for this phenomenon. In particular, that process can be represented by a fourth-order partial differential time-evolution logistic equation for the total plant biomass per unit area divided by the carrying capacity of its territory and defined on an unbounded flat spatial domain. Those patterns that consist of parallel stripes, labyrinth-like mazes, rhombic arrays of rectangular patches, and hexagonal distributions of spots or gaps are generated by the balance between the effects of short-range facilitation and long-range competition. Then those theoretical predictions are compared with both relevant observational evidence and existing numerical simulations as well as placed in the context of the results from some recent nonlinear pattern formation studies.