Species assortment or habitat filtering: a case study of spider communities on lake islands

Competition theory predicts that species of similar ecological niches are less likely to coexist than species with different niches, a process called species assortment. In contrast, the concept of habitat filtering implies that species with similar ecological requirements should co-occur more often than expected by chance. Here we use environmental and ecological data to assess patterns of co-occurrence of regional communities of spiders distributed across two assemblies of lake islands in northern Poland. We found aggregated and random co-occurrences of species of the same genus and a significant tendency of species segregation across genera. We also found that species of the same genus react similarly to important environmental variables. A comparison of ecological traits of species of the local communities with those expected from a random sample from the regional Polish species pool corroborated partly the habitat filtering hypothesis. On the other hand, we did not find evidence for species assortment. Our results also imply that at least some observed species co-occurrences result from niche differentiation.     

Tropical wetlands: seasonal hydrologic pulsing,carbon sequestration,and methane emissions

This paper summarizes the importance of climate on tropical wetlands. Regional hydrology and carbon dynamics in many of these wetlands could shift with dramatic changes in these major carbon storages if the inter-tropical convergence zone (ITCZ) were to change in its annual patterns. The importance of seasonal pulsing hydrology on many tropical wetlands, which can be caused by watershed activities, orographic features, or monsoonal pulses from the ITCZ, is illustrated by both annual and 30-year patterns of hydrology in the Okavango Delta in southern Africa. Current studies on carbon biogeochemistry in Central America are attempting to determine the rates of carbon sequestration in tropical wetlands compared to temperate wetlands and the effects of hydrologic conditions on methane generation in these wetlands. Using the same field and lab techniques, we estimated that a humid tropical wetland in Costa Rica accumulated 255 g C m⁻² year⁻¹ in the past 42 years, 80% more than a similar temperate wetland in Ohio that accumulated 142 g C m⁻² year⁻¹ over the same period. Methane emissions averaged 1,080 mg-C m⁻² day⁻¹ in a seasonally pulsed wetland in western Costa Rica, a rate higher than methane emission rates measured over the same period from humid tropic wetlands in eastern Costa Rica (120–278 mg-C m⁻² day⁻¹). Tropical wetlands are often tuned to seasonal pulses of water caused by the seasonal movement of the ITCZ and are the most likely to be have higher fire frequency and changed methane emissions and carbon oxidation if the ITCZ were to change even slightly.     

Pectolytic Bacteria Associated with Soft Rot of Calla Lily (Zantedeschia spp.) Tubers

Soft rot is the most important disease on calla lily in Poland. The isolation of the presumptive pathogen from symptomatic tubers on nutrient agar yielded bacteria with different colony morphology. Of 41 isolates collected, 10 showed pectolytic activity on crystal violet pectate medium and caused soft rot on potato slices. All pectolytic bacteria appeared to be Gram‐negative rods producing typical soft rot on inoculated leaf petioles of calla lily. Bacteria with colonies which morphologically resembled those used for inoculation were re‐isolated from diseased petioles. Their identification was based on phenotypic characters and sequence of the gene fragment coding 16S rRNA. It was found that, in addition to Pectobacterium carotovorum subsp. carotovorum, soft rot of calla lily can be caused by Pectobacterium carotovorum subsp. atrosepticum, Pseudomonas marginalis, Pseudomonas veronii and Chryseobacterium indologenes. The latter two are described for the first time as plant pathogens. The pectolytic activity of all identified bacteria, except that of P. carotovorum subsp. atrosepticum, was lower than that of P. carotovorum subsp. carotovorum, but strains of P. veronii showed a higher activity than P. marginalisand C. indologenes species.     

In vitro antiproliferative and antifungal activity of essential oils from Erigeron acris L. and Erigeron annuus (L.) Pers

Antiproliferative and antifungal activities of essential oils from Erigeron acris root and herb and from Erigeron annuus herb were investigated. The cell viability assay was performed in cultured fibroblasts, cancer cell lines (MCF-7 and MDA-MBA-231), and endometrial adenocarcinoma (Ishikawa) cells as well as colon adenocarcinoma (DLD-1) cells using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The essential oil from E. acris root showed the highest antiproliferative activity in the MCF-7 cell line with an IC50 value of 14.5 microg/mL. No effect of the essential oil on normal cells at that concentration was found. Antifungal activity against various strains of five Candida species, i.e. C. albicans, C. glabrata, C. tropicalis, C. krusei, and C. parapsilosis, was tested by the microdilution method. It was found that all examined oils can be useful as antifungal agents against the above-mentioned species, but the essential oil of E. acris herb was the most active. Their minimum inhibitory concentrations (MIC) ranged from 30 to 0.4 microL/mL. The data presented suggest that essential oils from E. acris and E. annuus possess antifungal activity against Candida spp. and antiproliferative activity against breast cancer MCF-7 cells.     

Methods of the site-selective solid phase synthesis of peptide-derived Amadori products

Two procedures of glycated peptides’ synthesis have been developed. The first method involves reductive alkylation of the ε-amino groups of lysine with 2,3:4,5-di-O-isopropylidene-β-d-arabino-hexos-2-ulo-2,6-pyranose in the presence of sodium cyanoborohydride on solid support. The second one uses a new fully protected lysine derivative, which is a building block designed for direct introduction of the glycated lysine moiety into a peptide, according to the standard solid phase synthesis protocol. The applicability of the proposed methods for the synthesis of peptide-derived Amadori products is discussed. The structure of the synthesized glycated peptides was confirmed by high-resolution mass spectrometry and enzymatic hydrolysis. Circular dichroism studies, performed in water solution, revealed that the formation of the Amadori rearrangement product in the lysine side chain does not influence significantly the conformational preferences of the peptides studied. However, when the solvent was changed to trifluoroethanol, the glycated peptides preferred β-turn conformation.     

S-Nitrosylation of Drp1 links excessive mitochondrial fission to neuronal injury in neurodegeneration

Neurons are known to use large amounts of energy for their normal function and activity. In order to meet this demand, mitochondrial fission, fusion, and movement events (mitochondrial dynamics) control mitochondrial morphology, facilitating biogenesis and proper distribution of mitochondria within neurons. In contrast, dysfunction in mitochondrial dynamics results in reduced cell bioenergetics and thus contributes to neuronal injury and death in many neurodegenerative disorders, including Alzheimer’s disease (AD), Parkinson’s disease, and Huntington’s disease. We recently reported that amyloid-β peptide, thought to be a key mediator of AD pathogenesis, engenders S-nitrosylation and thus hyperactivation of the mitochondrial fission protein Drp1. This activation leads to excessive mitochondrial fragmentation, bioenergetic compromise, and synaptic damage in models of AD. Here, we provide an extended commentary on our findings of nitric oxide-mediated abnormal mitochondrial dynamics.     

Fast and Forceful Refolding of Stretched α-Helical Solenoid Proteins

Anfinsen's thermodynamic hypothesis implies that proteins can encode for stretching through reversible loss of structure. However, large in vitro extensions of proteins that occur through a progressive unfolding of their domains typically dissipate a significant amount of energy, and therefore are not thermodynamically reversible. Some coiled-coil proteins have been found to stretch nearly reversibly, although their extension is typically limited to 2.5 times their folded length. Here, we report investigations on the mechanical properties of individual molecules of ankyrin-R, β-catenin, and clathrin, which are representative examples of over 800 predicted human proteins composed of tightly packed α-helical repeats (termed ANK, ARM, or HEAT repeats, respectively) that form spiral-shaped protein domains. Using atomic force spectroscopy, we find that these polypeptides possess unprecedented stretch ratios on the order of 10-15, exceeding that of other proteins studied so far, and their extension and relaxation occurs with minimal energy dissipation. Their sequence-encoded elasticity is governed by stepwise unfolding of small repeats, which upon relaxation of the stretching force rapidly and forcefully refold, minimizing the hysteresis between the stretching and relaxing parts of the cycle. Thus, we identify a new class of proteins that behave as highly reversible nanosprings that have the potential to function as mechanosensors in cells and as building blocks in springy nanostructures. Our physical view of the protein component of cells as being comprised of predominantly inextensible structural elements under tension may need revision to incorporate springs.     

The presence and polymorphism of genes encoding serine protease autotransporters (spate) among the Escherichia coli isolated in the region of Gdansk from children with diarrhea

The group of 96 strains ofEscherichia coli isolated from children with diarrhea were investigated towards the presence and polymorphism of genes encoding autotransporters that belong to the group of proteins named SPATE (Serine Protease Autotransporters ofEnterobacteriaceae). Based on the results of restriction analysis of the products of PCR reaction 8 different types of genes encoding SPATE were detected. It was found that 39 strains contained one gene of SPATE, 15 strains contained two different genes and 3 different genes were detected in the case of 3 strains. The analysis of combination of presence of genes encoding SPATE let us divide the investigated group of strains into 17 different genotypes. The analysis of polymorphism of genes encoding SPATE seems to be very promising tool for exploring the genetic diversity among pathogenic E. coli.