Enzymatic activity of the Staphylococcus aureus SplB serine protease is induced by substrates containing the sequence Trp-Glu-Leu-Gln

Proteases are of significant importance for the virulence of Staphylococcus aureus. Nevertheless, their subset, the serine protease-like proteins, remains poorly characterized. Here presented is an investigation of SplB protease catalytic activity revealing that the enzyme possesses exquisite specificity and only cleaves efficiently after the sequence Trp-Glu-Leu-Gln. To understand the molecular basis for such selectivity, we solved the three-dimensional structure of SplB to 1.8 Å. Modeling of substrate binding to the protease demonstrated that selectivity relies in part on a canonical specificity pockets-based mechanism. Significantly, the conformation of residues that ordinarily form the oxyanion hole, an essential structural element of the catalytic machinery of serine proteases, is not canonical in the SplB structure. We postulate that within SplB, the oxyanion hole is only formed upon docking of a substrate containing the consensus sequence motif. It is suggested that this unusual activation mechanism is used in parallel with classical determinants to further limit enzyme specificity. Finally, to guide future development, we attempt to point at likely physiological substrates and thus the role of SplB in staphylococcal physiology.     

Tomato tolerance to abiotic stress: a review of most often engineered target sequences

Tomato is one of the most often cultivated vegetable species worldwide. Due to the anti-oxidative and anti-cancer properties of lycopene, tomato consumption as well as production is still increasing. However, its productivity is impaired by a wide range of abiotic stresses, and the establishment of stress-tolerant crops is a key challenge for agricultural biotechnology. Until now, a few genetic approaches have been used to achieve stress tolerance in cultivated tomato plants. Such achievements are based on current knowledge concerning plant adaptation. The presence of adverse environmental factors like extreme temperatures, salinity or drought cause definite biochemical and physiological consequences. Mostly, these are the changes in the metabolic pathways, the expression of stress-inducible genes or the accumulation of low-molecular compounds that play a crucial role in maintaining the plasticity of reactions. The biotechnological methods used to modify tomato to produce “upgraded” plants are based on introgression of several genes coding enzymes known to mitigate stress or genes contributing to signalling and diverse regulatory pathways. Here, we present an overview of the most often chosen target sequences/molecules that are genetically delivered or engineered to obtain tolerance to environmental constraints. Since adverse conditions cause interrelated stress responses, it is the tolerance molecular players that are consecutively presented in this paper rather than the typically reviewed division of stress types.     

Plant-derived EpCAM antigen induces protective anti-cancer response

Immunotherapy holds great promise for treatment of infectious and malignant diseases and might help to prevent the occurrence and recurrence of cancer. We produced a plant-derived tumor-associated colorectal cancer antigen EpCAM (pGA733) at high yields using two modern plant expression systems. The full antigenic domain of EpCAM was efficiently purified to confirm its antigenic and immunogenic properties as compared to those of the antigen expressed in the baculovirus system (bGA733). Recombinant plant-derived antigen induced a humoral immune response in BALB/c mice. Sera from those mice efficiently inhibited the growth of SW948 colorectal carcinoma cells xenografted in nude mice, as compared to the EpCAM-specific mAb CO17-1A. Our results support the feasibility of producing anti-cancer recombinant vaccines using plant expression systems.     

<Emphasis Type="Italic">Streptomyces sudanensis</Emphasis> sp. nov., a new pathogen isolated from patients with actinomycetoma

Nine strains isolated from mycetoma patients and received as Streptomyces somaliensis were the subject of a polyphasic taxonomic study. The organisms shared chemical markers consistent with their classification in the genus Streptomyces and formed two distinct monophyletic subclades in the Streptomyces 16S rRNA gene tree. The first subclade contained four organisms, including the type strain of S. somaliensis, and the second clade the remaining five strains which had almost identical 16S rRNA sequences. Members of the two subclades were sharply separated using DNA:DNA relatedness and phenotypic data which also showed that the subclade 1 strains formed an heterogeneous group. In contrast, the subclade 2 strains were assigned to a single genomic species and had identical phenotypic profiles. It is evident from these data that the subclade 2 strains should be recognised as a new species of Streptomyces. The name proposed for this new species is Streptomyces sudanensis sp. nov. The type strain is SD 504^T (DSM = 41923^T = NRRL B-24575^T). Erika T. Quintana and Katarzyna Wierzbicka contributed equally to this work. The GenBank accession numbers for the 16S rRNA gene sequences of Streptomyces somaliensis DSM 40738^T and Streptomyces sudanensis DSM 41607, DSM 41608, DSM 41609, SD 504^T and SD 509 are EF540897, EF540898, EF540999, EF515876 and EF540900.     

Selenium levels in blood of Upper Silesian population

The selenium status and the relationship of whole-blood selenium and plasma homocysteine are reported for healthy human subjects living in Upper Silesia. A total of 1063 individuals (627 male and 436 female) examined for whole-blood selenium were subdivided into six groups according to age; the youngest included adolescents (n=143) aged 10–15 yr, and the oldest were centenarians (n=132). The mean Se content was relatively low (62.5±18.4 μg/L), and it tended to be higher in men (65.9±17.2 μg/L) than in women (57.5±18.9 μg/L). Selenium levels appeared to be age dependent, as the highest values were observed in young and middle-age adults (21–40 yr), whereas they were significantly lower in adolescents and in the elderly. In more than 40% of apparently healthy adults (aged 21–69 yr), the Se concentration was within the range 60–80 μg/L (i.e., below the lower limit of the nutritional adequacy range [80 μg/L]). A significant inverse correlation between whole-blood selenium and plasma total homocysteine was detected in a smaller population sample of middle-aged and elderly persons (n=204).     

Genetic evidence of reproductive isolation in a remote enclave of Quercus pubescens in the presence of cross-fertile species

Peripheral populations may be crucial for understanding processes underlying adaptive genetic variation. Their evolution and ecology are driven by various genetic and demographic processes, such as selection, gene flow and bottleneck. Peripheral populations often experience a reduction in density resulting in the Allee effect. The presence of interfertile species increases the opportunity for hybridisation, which allows for a rescue from the Allee effect, but at the risk of genetic extinction through introgression. In this article we investigated a peripheral population of Quercus pubescens, a European tree species. The study population is located in Poland, several hundred kilometres northwards from the main species range. Due to geographic separation, the study population exists under strong pressure of introgression from potentially inter-fertile Q. petraea and Q. robur, which are the only common oaks in Poland. The intermediate morphology between typical Q. pubescens and a common oak species found in the study population supports the introgression hypothesis, which could be in line with the earlier studies of this species complex conducted in the main range of Q. pubescens. Alternatively, the intermediate morphology could reflect the founder effect or selection at an ecological extreme. We attempted to verify these hypotheses using microsatellites and a reference of common oak species. The results showed that the study population is genetically distinct from both Q. petraea and Q. robur. Additionally, the population is characterised by a low effective population size and limited gene dispersal. This suggests that the study population reveals strong reproductive isolation from common species, implying alternative sources of atypical morphology.     

Activity of beavers as an ecological factor that affects the benthos of small rivers - a case study in the Żylica River (Poland)

The Eurasian beaver (Castor fiber) has a greater impact on local ecosystems than other herbivores, and the affected area exceeds the range of its presence. Its activity may change or create new habitats by modifying the availability of the biotic and abiotic resources available not only to beavers, but also to other groups of animals. Our aim was to study how beaver activity affects the benthos composition in a small river and in a beaver pond. The way in which beavers function in the case of small rivers has received little attention. The study showed a lower density of benthos above the dam (beaver pond - 1467 ind./m²) compared to the river (3147 ind./m²). Below the dam, the diversity of Trichoptera and Coleoptera was greater, while Diptera were more abundant in the beaver pond. Betidae were a constant component in the benthos assemblages and were most abundant in the beaver pond. Collectors-gatherers and predators were the most numerous in the beaver pond. Decreasing percentages of collectors-gatherers were observed with an increased abundance of collectors-filterers and shredders in the river. All of the ratio values except the P/T FFG (Predators to total of all other groups) were lower in the beaver pond compared to the river. The % EPT (Ephemeroptera Plecoptera and Trichoptera) was also greater in the beaver pond. Small differences in the physicochemical properties of the water and organic matter content in the bottom sediments were found both above and below the beaver dam.     

Influenza Hemifusion Phenotype Depends on Membrane Context: Differences in Cell–Cell and Virus–Cell Fusion

Influenza viral entry into the host cell cytoplasm is accomplished by a process of membrane fusion mediated by the viral hemagglutinin protein. Hemagglutinin acts in a pH-triggered fashion, inserting a short fusion peptide into the host membrane followed by refolding of a coiled-coil structure to draw the viral envelope and host membranes together. Mutations to this fusion peptide provide an important window into viral fusion mechanisms and protein–membrane interactions. Here, we show that a well-described fusion peptide mutant, G1S, has a phenotype that depends strongly on the viral membrane context. The G1S mutant is well known to cause a “hemifusion” phenotype based on experiments in transfected cells, where cells expressing G1S hemagglutinin can undergo lipid mixing in a pH-triggered fashion similar to virus but will not support fusion pores. We compare fusion by the G1S hemagglutinin mutant expressed either in cells or in influenza virions and show that this hemifusion phenotype occurs in transfected cells but that native virions are able to support full fusion, albeit at a slower rate and 10–100 × reduced infectious titer. We explain this with a quantitative model where the G1S mutant, instead of causing an absolute block of fusion, alters the protein stoichiometry required for fusion. This change slightly slows fusion at high hemagglutinin density, as on the viral surface, but at lower hemagglutinin density produces a hemifusion phenotype. The quantitative model thus reproduces the observed virus–cell and cell–cell fusion phenotypes, yielding a unified explanation where membrane context can control the observed viral fusion phenotype.     

Selected Species of the Genus Phellinus – Chemical Composition,Biological Activity,and Medicinal Applications

This study presents the current knowledge on chemical composition, biological activity, and possible medicinal applications of Phellinus igniarius, Phellinus pini, Phellinus pomaceus, and Phellinus robustus. These inedible arboreal species are phytopathogens that cause the enzymatic decomposition of wood. These species belong to the medicinal mushrooms and have been known for centuries in the traditional medicine of the Far East. They have been used as an effective remedy for stomach and intestinal ailments, diarrhea, and hemorrhages. Mycochemical studies have proved the presence of polysaccharides, phenolic compounds, and terpenoids. These compounds show biological activities such as anticancer, antioxidant, antiangiogenic, and antiviral. Research studies conducted using modern analytical methods have advanced the knowledge on the potential therapeutic use of compounds isolated not only from the fruiting bodies but also from biomass obtained with in vitro biotechnological methods.