Ecological variation between marginal and central populations of Potamogeton polygonifolius,a rare and endangered species in Central Europe

The present study is focused on Potamogeton polygonifolius – the species considered to be endangered in Germany, the Czech Republic, Poland and Switzerland. Field studies were carried out in Lower Silesia and Lusatia in southwestern Poland in order to verify the present state of the marginal populations of P. polygonifolius, to determine the habitat preferences of the species in the study area, to compare the ecological data between marginal and central populations and finally to recognise the factors constraining the easternmost limit of the P. polygonifolius. In total, 18 populations were examined, and 11 relevés were collected. The relevés gathered were compared with 95 relevés made in northwestern Germany, and with 10 relevés collected in the German part of Lusatia. There were no significant differences between the ecology of populations of P. polygonifolius on the eastern edge of its range and those in the central part. P. polygonifolius was found growing both in natural habitats like unspoiled peat bogs, and in anthropogenic habitats such as exploited peat bogs and drainage ditches. In both types of habitats its populations were abundant and competent in terms of generative propagation. The lack of geographical barriers as well as biology and fitness of P. polygonifolius individuals from the study area suggest that marginal populations are possibly a part of a large metapopulation, covering the whole (Polish and German) area of Lusatia, however, this hypothesis was not tested in detail. The main factor shaping the easternmost limit of the general range of P. polygonifolius is most likely climate, which prevents P. polygonifolius from spreading farther eastwards.     

Inhibitor of Transfer Ribonucleic Acid Methylases in the Differentiating Slime Mold Dictyostelium discoideum

Eight hours after the onset of morphogenesis, an inhibitor of transfer ribonucleic acid methylases appears in differentiating Dictyostelium discoideum. The inhibitor is also present in spores. Fifty per cent of the inhibiting activity is lost upon heating at 100 C for 5 min; it is nondialyzable and sensitive to trypsin.     

Rab11-FIP3 is critical for the structural integrity of the endosomal recycling compartment

Rab11-FIP3 is an endosomal recycling compartment (ERC) protein that is implicated in the process of membrane delivery from the ERC to sites of membrane insertion during cell division. Here we report that Rab11-FIP3 is critical for the structural integrity of the ERC during interphase. We demonstrate that knockdown of Rab11-FIP3 and expression of a mutant of Rab11-FIP3 that is Rab11-binding deficient cause loss of all ERC-marker protein staining from the pericentrosomal region of A431 cells. Furthermore, we find that fluorophore-labelled transferrin cannot access the pericentrosomal region of cells in which Rab11-FIP3 function has been perturbed. We find that this Rab11-FIP3 function appears to be specific because expression of the equivalent Rab11-binding deficient mutant of Rab-coupling protein does not perturb ERC morphology. In addition, we find that other organelles such as sorting and late endosomes are unaffected by loss of Rab11-FIP3 function. Finally, we demonstrate the presence of an extensive coiled-coil region between residues 463 and 692 of Rab11-FIP3, which exists as a dimer in solution and is critical to support its function on the ERC. Together, these data indicate that Rab11-FIP3 is necessary for the structural integrity of the pericentrosomal ERC.     

The architectonics of programmable RNA and DNA nanostructures

The past several years have witnessed the emergence of a new world of nucleic-acid-based architectures with highly predictable and programmable self-assembly properties. For almost two decades, DNA has been the primary material for nucleic acid nanoconstruction. More recently, the dramatic increase in RNA structural information led to the development of RNA architectonics, the scientific study of the principles of RNA architecture with the aim of constructing RNA nanostructures of any arbitrary size and shape. The remarkable modularity and the distinct but complementary nature of RNA and DNA nanomaterials are revealed by the various self-assembly strategies that aim to achieve control of the arrangement of matter at a nanoscale level.     

A 3-D model of tumor progression based on complex automata driven by particle dynamics

The dynamics of a growing tumor involving mechanical remodeling of healthy tissue and vasculature is neglected in most of the existing tumor models. This is due to the lack of efficient computational framework allowing for simulation of mechanical interactions. Meanwhile, just these interactions trigger critical changes in tumor growth dynamics and are responsible for its volumetric and directional progression. We describe here a novel 3-D model of tumor growth, which combines particle dynamics with cellular automata concept. The particles represent both tissue cells and fragments of the vascular network. They interact with their closest neighbors via semi-harmonic central forces simulating mechanical resistance of the cell walls. The particle dynamics is governed by both the Newtonian laws of motion and the cellular automata rules. These rules can represent cell life-cycle and other biological interactions involving smaller spatio-temporal scales. We show that our complex automata, particle based model can reproduce realistic 3-D dynamics of the entire system consisting of the tumor, normal tissue cells, blood vessels and blood flow. It can explain phenomena such as the inward cell motion in avascular tumor, stabilization of tumor growth by the external pressure, tumor vascularization due to the process of angiogenesis, trapping of healthy cells by invading tumor, and influence of external (boundary) conditions on the direction of tumor progression. We conclude that the particle model can serve as a general framework for designing advanced multiscale models of tumor dynamics and it is very competitive to the modeling approaches presented before.     

A new rapid and cost-effective method for detection of phages, ICEs and virulence factors encoded by Streptococcus pyogenes

Streptococcus pyogenes (group A Streptococcus, GAS) is a human pathogen that causes diseases of various intensity, from mild strep throat to life threatening invasive infections and postinfectional sequelae. S. pyogenes encodes multiple, often phage encoded, virulence factors and their presence is related to severity of the disease. Acquisition of mobile genetic elements, carrying virulence factors, as phages or ICEs (integrative and cojugative elements) has been shown previously to promote selection of virulent clones. We designed the system of eight low volume multi- and one singleplex PCR reactions to detect genes encoding twenty virulence factors (spd3, sdc, sdaB, sdaD, speB, spyCEP, scpA, mac, sic, speL, K, M, C, I, A, H, G, J, smeZ and ssa) and twenty one phage and ICE integration sites described so far for S. pyogenes. Classification of strains based on the phage and virulence factors absence or presence, correlates with PFGE MLST and emm typing results. We developed a novel, fast and cost effective system that can be used to detect GAS virulence factors. Moreover, this system may become an alternative and effective system to differentiate between GAS strains.