Subcellular distribution of glutathione and cysteine in cyanobacteria

Glutathione plays numerous important functions in eukaryotic and prokaryotic cells. Whereas it can be found in virtually all eukaryotic cells, its production in prokaryotes is restricted to cyanobacteria and proteobacteria and a few strains of gram-positive bacteria. In bacteria, it is involved in the protection against reactive oxygen species (ROS), osmotic shock, acidic conditions, toxic chemicals, and heavy metals. Glutathione synthesis in bacteria takes place in two steps out of cysteine, glutamate, and glycine. Cysteine is the limiting factor for glutathione biosynthesis which can be especially crucial for cyanobacteria, which rely on both the sufficient sulfur supply from the growth media and on the protection of glutathione against ROS that are produced during photosynthesis. In this study, we report a method that allows detection and visualization of the subcellular distribution of glutathione in Synechocystis sp. This method is based on immunogold cytochemistry with glutathione and cysteine antisera and computer-supported transmission electron microscopy. Labeling of glutathione and cysteine was restricted to the cytosol and interthylakoidal spaces. Glutathione and cysteine could not be detected in carboxysomes, cyanophycin granules, cell walls, intrathylakoidal spaces, periplasm, and vacuoles. The accuracy of the glutathione and cysteine labeling is supported by two observations. First, preadsorption of the antiglutathione and anticysteine antisera with glutathione and cysteine, respectively, reduced the density of the gold particles to background levels. Second, labeling of glutathione and cysteine was strongly decreased by 98.5% and 100%, respectively, in Synechocystis sp. cells grown on media without sulfur. This study indicates a strong similarity of the subcellular distribution of glutathione and cysteine in cyanobacteria and plastids of plants and provides a deeper insight into glutathione metabolism in bacteria

Numerical modelling of nonlinear extreme waves in the presence of wind

A numerical wave flume with fully nonlinear free surface boundary conditions is adopted to investigate the temporal characteristics of extreme waves in the presence of wind at various speeds. Incident wave trains are numerically generated by a piston-type wave maker, and the wind-excited pressure is introduced into dynamic boundary conditions using a pressure distribution over steep crests, as defined by Jeffreys’ sheltering mechanism. A boundary value problem is solved by a higher-order boundary element method (HOBEM) and a mixed Eulerian-Lagrangian time marching scheme. The proposed model is validated through comparison with published experimental data from a focused wave group. The influence of wind on extreme wave properties, including maximum extreme wave crest, focal position shift, and spectrum evolution, is also studied. To consider the effects of the wind-driven currents on a wave evolution, the simulations assume a uniform current over varying water depth. The results show that wind causes weak increases in the extreme wave crest, and makes the nonlinear energy transfer non-reversible in the focusing and defocusing processes. The numerical results also provide a comparison to demonstrate the shifts at focal points, considering the combined effects of the winds and the wind-driven currents

A small fossil fish fauna, rich in Chlamydoselachus teeth, from the Late Pliocene of Tuscany (Siena, central Italy)

A small elasmobranch teeth and teleost otolith assemblage from the Piacenzian-earliest Gelasian of Tuscany (Castelnuovo Berardenga Scalo, Siena province, Italy) is described. The exceptional abundance of teeth belonging to Cizlamydoselaclms lawleyi Davis, 1887 has enabled us to better define and confirm the validity of this doubtful fossil taxon.ln agreement with Davis (1887) and Ffeil ( 1983) this species appears lo differ from the living frilled shark C. anguìneus Garman, 1884 at least by its larger size. Palaeoecological inferences based on the ecology of C. anguineus together with deep water sharks such as Cellfrophorus granulosus (Bloch & Schneider, 1801) and the teleost otolith assemblage mainly characterised by macrourids and myctophids enable us to configure, in the Pìacenzian to earlìest Gelasian of Tuscany (Siena subbasin of the Siena-Radicofani Basin) an upper bathyal slope palaeoenvironment. The occurrence of Chlamydoselaclms in the Piacenzian-earliest Gelasian ofthe Mediterranean palaeo-area demonstrates the persistence of an oceanic environment not as profusely developed as during the early Zanclean (i.e. lower part of MPL 2 foraminiferal biozone; see Cigala Fulgosi, 1986, 1996)

A novel multi-functional chloroplast protein: identification of a 40 kDa immunophilin-like protein located in the thylakoid lumen.

We describe the identification of the first immunophilin associated with the photosynthetic membrane of chloroplasts. This complex 40 kDa immunophilin, designated TLP40 (thylakoid lumen PPIase), located in the lumen of the thylakoids, was found to play a dual role in photosynthesis involving both biogenesis and intraorganelle signalling. It originates in a single-copy nuclear gene, is made as a precursor of 49.2 kDa with a bipartite lumenal targeting transit peptide, and is characterized by a structure including a cyclophilin-like C-terminal segment of 20 kDa, a predicted N-terminal leucine zipper and a potential phosphatase-binding domain. It can exist in different oligomeric conformations and attach to the inner membrane surface. It is confined predominantly to the non-appressed thylakoid regions, the site of protein integration into the photosynthetic membrane. The isolated protein possesses peptidyl-prolyl cis-trans isomerase protein folding activity characteristic of immunophilins, but is not inhibited by cyclosporin A. TLP40 also exerts an effect on dephosphorylation of several key proteins of photosystem II, probably as a constituent of a transmembrane signal transduction chain. This first evidence for a direct role of immunophilins in a photoautotrophic process suggests that light-mediated protein phosphorylation in photosynthetic membranes and the role of the thylakoid lumen are substantially more complex than anticipated

Modeling the Incubation Effect Among Students Playing an Educational Game for Physics

We attempted to model the Incubation Effect, a phenomenon in which a momentary break helps the generation of a solution to a problem, among students playing Physics Playground. We performed a logistic regression analysis to predict the outcome of the incubation using a genetic algorithm for feature selection. Out of 14 candidate features, those that significantly predicted the outcome were total badges earned prior to post-incubation, the problem’s level of difficulty, total attempts made prior to post-incubation, and time interval of post-incubation. We found evidence that incubation in the earlier part of the game is more beneficial than breaks at the later part where students may already be mentally exhausted