Plasmodium falciparum RuvB1 is an active DNA helicase and translocates in the 5′–3′ direction

RuvB family of protein contains two similar kinds of proteins i.e. RuvB1 and RuvB2 from yeast to human. These proteins belong to the AAA + class of proteins and are critical components of several multiprotein complexes involved in diverse cellular activities. There are two RuvB proteins annotated in the Plasmodium database but the identification of the third protein recently by our lab has raised the question why Plasmodium falciparum contains three RuvB proteins instead of two. Hence the biochemical characterizations of these proteins have become essential to understand the role of these proteins in the malaria parasite. Recently we have reported the characterization of the recombinant PfRuvB3, which contains ATPase activity but lacks DNA helicase activity. In the present study we report the phylogenetic analysis and detailed biochemical characterization of one of the other RuvB homologue RuvB1 from P. falciparum. PfRuvB1 shows considerable homology with human as well as yeast RuvB1 and contains Walker motif A and Walker motif B. The activity analysis of this protein revealed that PfRuvB1 is an ATPase and this activity increased significantly in the presence of ss-DNA. PfRuvB1 also contains DNA helicase activity and translocates preferentially in 5′ to 3′ direction. In vivo investigation of PfRuvB1 revealed that it is constitutively expressed during all the stages of intraerythrocytic cycle of P. falciparum and localizes mainly to the nucleus. These studies will make important contribution in understanding the role of RuvB protein in P. falciparum.     

Conditioning of surfaces by macromolecules and its implication for the settlement of zoospores of the green alga Ulva linza

Conditioning, ie the adsorption of proteins and other macromolecules, is the first process that occurs in the natural environment once a surface is immersed in seawater, but no information is available either regarding the conditioning of surfaces by artificial seawater or whether conditioning affects data obtained from laboratory assays. A range of self-assembled monolayers (SAMs) with different chemical terminations was used to investigate the time-dependent formation of conditioning layers in commercial and self-prepared artificial seawaters. Subsequently, these results were compared with conditioning by solutions in which zoospores of the green alga Ulva linza had been swimming. Spectral ellipsometry and contact angle measurements as well as infrared reflection absorption spectroscopy (IRRAS) were used to reveal the thickness and chemical composition of the conditioning layers. The extent that surface preconditioning affected the settlement of zoospores of U. linza was also investigated. The results showed that in standard spore settlement bioassays (45–60 min), the influence of a molecular conditioning layer is likely to be small, although more substantial effects are possible at longer settlement times.     

Review – Interactions between diatoms and stainless steel: focus on biofouling and biocorrosion

There is a considerable body of information regarding bacterially enhanced corrosion, however, this review focuses on diatoms (unicellular algae) whose contribution to biocorrosion is less well studied. The reasons why diatoms have been neglected in studies of biocorrosion in natural waters are discussed and the question whether diatoms should be considered as inert with respect of electrochemical processes is considered. A particular focus is given to the case of stainless steels (SS), which are widely used in variety of applications in natural waters. Basic information on the cell biology of diatoms is included in the review, particularly with respect to their ability to ‘sense’ and adhere to surfaces. Investigations at the nanoscale are reviewed as these studies provide information about the behavior of cells at interfaces. Recent advances include the use of atomic force microscopy (AFM), although only a few studies have been applied to diatoms. Regarding the electrochemical behavior of SS, the mechanisms by which diatoms influence the potential ennoblement process is discussed. Such studies reveal the association of diatoms, in addition to bacteria, with biocorrosion processes.     

Lubrication and load-bearing properties of human salivary pellicles adsorbed ex vivo on molecularly smooth substrata

In a series of Surface Force Balance experiments, material from human whole saliva was adsorbed to molecularly smooth mica substrata (to form an ‘adsorbed salivary film’). Measurements were taken of normal (load bearing, F _n) and shear (frictional, F _s*) forces between two interacting surfaces. One investigation involved a salivary film formed by overnight adsorption from undiluted, centrifuged saliva, with the adsorbed film rinsed with pure water before measurement. Measurements were taken under pure water and 70 mM NaNO₃. In a second investigation, a film was formed from and measured under a solution of 7% filtered saliva in 10 mM NaNO₃. F _n results for both systems showed purely repulsive layers, with an uncompressed thickness of 35–70 nm for the diluted saliva investigation and, prior to the application of shear, 11 nm for the rinsed system. F _s* was essentially proportional to F _n for all systems and independent of shear speed (in the range 100–2000 nm s^?1), with coefficients of friction  μ ～ 0.24 and μ ～ 0.46 for the unrinsed and rinsed systems, respectively. All properties of the rinsed system remained similar when the pure water measurement environment was changed to 70 mM NaNO₃. For all systems studied, shear gave rise to an approximately threefold increase in the range of normal forces, attributed to the ploughing up of adsorbed material during shear to form debris that stood proud of the adsorbed layer. The results provide a microscopic demonstration of the wear process for a salivary film under shear and may be of particular interest for understanding the implications for in vivo oral lubrication under conditions such as rinsing of the mouth cavity. The work is interpreted in light of earlier studies that showed a structural collapse and increase in friction for an adsorbed salivary film in an environment of low ionic strength.     

Ontogenic study of the brachiopod Dicoelosia by geometric morphometrics and morphing techniques

The distinctive brachiopod Dicoelosia King 1850 is characterized by a strongly bilobed outline. To date, studies have concentrated on its functional morphology, taxonomy and evolution; little attention has been paid to its ontogeny. Here, we map population variation by principal component analysis for over 80 specimens distributed across five species of Dicoelosia. Using geometric morphometrics with landmarks for some 40 specimens, the ontogenic trends in D. sp. nov. are compared with those of Dicoelosia biloba. In addition, the ontogenic pathway in D. sp. nov. is investigated by morphing with control points, a new technique introduced here to palaeontology. Combining the results above, the ontogeny of the key character of the genus, emargination, is modelled. Within single populations, taxa may develop from broad weakly emarginate forms into those that are elongate and deeply emarginate. As the identification of the genus and its species depends on external morphological characters, the definition of ontogenetic trends in each species is essential for taxonomic discrimination. Substantial population variation exists in many of its species; however, the morphing technique provides a method of simulation, predicting the full range of ontogenetic variation in given populations.     

Geometric morphometrics as a tool for interpreting evolutionary transitions in the black fly wing (Diptera: Simuliidae)

A geometric morphometric analysis was conducted on wing‐vein landmarks on exemplar species of the family Simuliidae of the following genera: Parasimulium, Gymnopais, Twinnia, Helodon, Prosimulium, Greniera, Stegopterna, Tlalocomyia, Cnephia, Ectemnia, Metacnephia, Austrosimulium, and Simulium. Generalized least squares superimposition was performed on landmarks, followed by a principal component analysis on resulting Procrustes distances. Patterns of shape change along the principal component axes were visualized using the thin‐plate spline. The analysis revealed wing shape diversity through (1) the insertion points of the subcosta and R₁, resulting in the terminus of the costa exhibiting a trend towards a more apical position on the wing, and (2) the insertion point of the humeral cross vein, resulting in the anterior branch of the media exhibiting a trend toward a more basal position on the wing. Canonical variates analysis of Procrustes distances successfully assigned all exemplar species into their a priori taxonomic groupings. The diversity in wing shape reveals a trend towards decreased length of basal radial cell and increased costalization of anterior wing veins in the evolutionary transition from plesiomorphic prosimuliines to more derived simuliines. The functional significance of these evolutionary transitions is discussed. © 2013 The Linnean Society of London     

Acetate supplementation increases brain phosphocreatine and reduces AMP levels with no effect on mitochondrial biogenesis

Acetate supplementation in rats increases plasma acetate and brain acetyl-CoA levels. Although acetate is used as a marker to study glial energy metabolism, the effect that acetate supplementation has on normal brain energy stores has not been quantified. To determine the effect(s) that an increase in acetyl-CoA levels has on brain energy metabolism, we measured brain nucleotide, phosphagen and glycogen levels, and quantified cardiolipin content and mitochondrial number in rats subjected to acetate supplementation. Acetate supplementation was induced with glyceryl triacetate (GTA) by oral gavage (6 g/kg body weight). Rats used for biochemical analysis were euthanized using head-focused microwave irradiation at 2, and 4 h following treatment to immediately stop metabolism. We found that acetate did not alter brain ATP, ADP, NAD, GTP levels, or the energy charge ratio [ECR, (ATP + ½ ADP)/(ATP + ADP + AMP)] when compared to controls. However, after 4 h of treatment brain phosphocreatine levels were significantly elevated with a concomitant reduction in AMP levels with no change in glycogen levels. In parallel studies where rats were treated with GTA for 28 days, we found that acetate did not alter brain glycogen and mitochondrial biogenesis as determined by measuring brain cardiolipin content, the fatty acid composition of cardiolipin and using quantitative ultra-structural analysis to determine mitochondrial density/unit area of cytoplasm in hippocampal CA3 neurons. Collectively, these data suggest that an increase in brain acetyl-CoA levels by acetate supplementation does increase brain energy stores however it has no effect on brain glycogen and neuronal mitochondrial biogenesis.     

Ratatouille: An Animated Account of Cooking,Taste, and Human Evolution

This paper analyzes the immensely popular animated film Ratatouille as a social and cultural document. It begins with a recapitulation of the movie's story line – a saga of an astute, ambitious and talented rat, who becomes transformed into an accomplished haute cuisine chef. The film illustrates recent anthropological writings on the central role of cooking in human evolution. It also shows how varieties of cooking and table manners provide key indications of the civilizing process. Ultimately, Ratatouille explores distinctions and similarities between “man and beast”. It communicates the idea that all living creatures share more in terms of aptitude and feeling than divides them.     

Texture formation in DNA films with alkali metal chlorides

The formation of textures in DNA films with LiCl, NaCl, KCl, RbCl, and CsCl salts has been studied. The films are prepared by evaporation of water solution with highly polymerized calf thymus DNA and excess salt of specific type. For DNA solution with 10 mM concentration of NaCl, KCl, and RbCl the films with dendritic textures have been obtained, whereas in case of CsCl the textures in the films appear only at 30 mM concentration of excess salt in the initial solution. In the solution with LiCl, the textures in DNA films have not been observed within the whole range of concentration of excess salt under consideration. The analysis of parameters of DNA films with different salts has showed that evaporation of solution leads to crystallization of salt ions on DNA macromolecule and formation of DNA‐salt complexes. Electrostatic energy of the system of crystalline ordered ions and charges of DNA chains has been estimated to study the stability of DNA‐salt complexes. The results obtained for different salts have been showed that the presence of DNA macromolecule enhances crystallization as compared with solution without DNA. The property of excess salt to form the crystalline structures has been found to decrease in the following order: KCl > NaCl > RbCl > CsCl > LiCl. The results of estimation are in good agreement with the experimentally observed dependence of texture formation on excess salt type. © 2013 Wiley Periodicals, Inc. Biopolymers 99: 508–516, 2013.     

The microalga Parachlorella kessleri––A novel highly efficient lipid producer

The alga Parachlorella kessleri, strain CCALA 255, grown under optimal conditions, is characterized by storage of energy in the form of starch rather than lipids. If grown in the complete medium, the cultures grew rapidly, producing large amounts of biomass in a relatively short time. The cells, however, contained negligible lipid reserves (1–10% of DW). Treatments inducing hyperproduction of storage lipids in P. kessleri biomass were described. The cultures were grown in the absence or fivefold decreased concentration of either nitrogen or phosphorus or sulfur. Limitation by all elements using fivefold or 10‐fold diluted mineral medium was also tested. Limitation with any macroelement (nitrogen, sulfur, or phosphorus) led to an increase in the amount of lipids; nitrogen limitation was the most effective. Diluted nutrient media (5‐ or 10‐fold) were identified as the best method to stimulate lipid overproduction (60% of DW). The strategy for lipid overproduction consists of the fast growth of P. kessleri culture grown in the complete medium to produce sufficient biomass (DW more than 10 g/L) followed by the dilution of nutrient medium to stop growth and cell division by limitation of all elements, leading to induction of lipid production and accumulation up to 60% DW. Cultivation conditions necessary for maximizing lipid content in P. kessleri biomass generated in a scale‐up solar open thin‐layer photobioreactor were described. Biotechnol. Bioeng. 2013; 110: 97–107. © 2012 Wiley Periodicals, Inc.