Bacteriophages engineered to display foreign peptides may become short-circulating phages

Bacteriophages draw scientific attention in medicine and biotechnology, including phage engineering, widely used to shape biological properties of bacteriophages. We developed engineered T4-derived bacteriophages presenting seven types of tissue-homing peptides. We evaluated phage accumulation in targeted tissues, spleen, liver and phage circulation in blood (in mice). Contrary to expectations, accumulation of engineered bacteriophages in targeted organs was not observed, but instead, three engineered phages achieved tissue titres up to 2 orders of magnitude lower than unmodified T4. This correlated with impaired survival of these phages in the circulation. Thus, engineering of T4 phage resulted in the short-circulating phage phenotype. We found that the complement system inactivated engineered phages significantly more strongly than unmodified T4, while no significant differences in phages’ susceptibility to phagocytosis or immunogenicity were found. The short-circulating phage phenotype of the engineered phages suggests that natural phages, at least those propagating on commensal bacteria of animals and humans, are naturally optimized to escape rapid neutralization by the immune system. In this way, phages remain active for longer when inside mammalian bodies, thus increasing their chance of propagating on commensal bacteria. The effect of phage engineering on phage pharmacokinetics should be considered in phage design for medical purposes.     

Expression of a glycosylated GFP as a bivalent reporter in exocytosis

The complex-type N-linked glycans of plants differ markedly in structure from those of animals. Like those of insects and mollusks they lack terminal sialic acid(s) and may contain an α-(1,3)-fucose (Fuc) linked to the proximal GlcNAc residue and/or a β-(1,2)-xylose (Xyl) residue attached to the proximal mannose (Man) of the glycan core. N-glycosylated GFPs were used in previous studies showing their effective use to report on membrane traffic between the ER and the Golgi apparatus in plant cells. In all these cases glycosylated tags were added at the GFP termini. Because of the position of the tag and depending on the sorting and accumulation site of these modified GFP, there is always a risk of processing and degradation, and this protein design cannot be considered ideal. Here, we describe the development of three different GFPs in which the glycosylation site is internally localized at positions 80, 133, or 172 in the internal sequence. The best glycosylation site was at position 133. This glycosylated GFPgl133 appears to be protected from undesired processing of the glycosylation site and represents a bivalent reporter for biochemical and microscopic studies. After experimental validation, we can conclude that amino acid 133 is an effective glycosylation site and that the GFPgl133 is a powerful tool for in vivo investigations in plant cell biology.     

Tattoo and piercing as signals of biological quality

Tattoos and non-conventional piercings are used in many societies. There are several social reasons for which people use these forms of body decorations (e.g., marking social status or signaling membership within a subculture). However, it is interesting why only some people within a group that uses body decoration as a badge of membership decide upon such decorations. Since both tattoos and piercings can present health risks (e.g., due to blood-borne disease transmission risk), we postulate that people who decide to have such a body decoration might have relatively higher biological quality and that tattoos/piercings can be an honest signal of genetic quality. The possible opposite hypothesis is the “attractiveness increase hypothesis,” according to which people use body decorations to increase their own physical attractiveness or to hide some shortcomings in their appearance (e.g., low body symmetry). To test these hypotheses, we compared body fluctuating asymmetry, which is considered a good measure of developmental stability, between individuals wearing tattoos and/or non-conventional piercings (n=116) and a control group (without such body decorations) (n=86). We found that majority of the absolute and relative fluctuating asymmetry indices had significantly lower values in individuals with tattoos/piercings than in the control group. This effect was strongly driven by males. Higher body symmetry of the men having tattoo or piercing indicates that this type of body decoration in the western society can be related to the honest signal of biological quality only for men. We did not find support for the “attractiveness increase hypothesis” for either sex.     

Yeast and other lower eukaryotic organisms for studies of Vps13 proteins in health and disease

Human Vps13 proteins are associated with several diseases, including the neurodegenerative disorder Chorea‐acanthocytosis (ChAc), yet the biology of these proteins is still poorly understood. Studies in Saccharomyces cerevisiae, Dictyostelium discoideum, Tetrahymena thermophila and Drosophila melanogaster point to the involvement of Vps13 in cytoskeleton organization, vesicular trafficking, autophagy, phagocytosis, endocytosis, proteostasis, sporulation and mitochondrial functioning. Recent findings show that yeast Vps13 binds to phosphatidylinositol lipids via 4 different regions and functions at membrane contact sites, enlarging the list of Vps13 functions. This review describes the great potential of simple eukaryotes to decipher disease mechanisms in higher organisms and highlights novel insights into the pathological role of Vps13 towards ChAc.      

Nuclear microsatellite markers reveal the low genetic structure of <Emphasis Type="Italic">Pinus mugo</Emphasis> Turra (dwarf mountain pine) populations in Europe

Twenty-one populations (555 individuals) covering the entire native range of Pinus mugo Turra (dwarf mountain pine) were investigated for genetic variation scored at 13 nuclear microsatellite markers (nSSRs). The main objective of the present study was to determine the genetic structure across the present distribution of the species and locate populations of different genetic compositions. Most of the genetic variation was observed within the populations (95%). The assignment of populations based on Bayesian clustering methods revealed that the Sudeten populations of P. mugo form a separate genetic cluster. These stands have likely been established through the founder effects of Alpine migrants. The distribution and level of SSR polymorphisms, along with no evidence of isolation by distance or phylogeographic structure, indicate that the present populations of P. mugo have diverged relatively recently and originate from a larger glacial distribution of the species. One peripheral stand from Italy had the lowest values of most calculated genetic variation indices. This stand could therefore be more susceptible to genetic drift and a negative impact of predicted environmental changes. We discuss our findings with respect to previously published results on the genetic and morphological variation of P. mugo and with consideration for the conservation genetics of the species.     

Long-term within-basin isolation patterns,different conservation units,and interspecific mitochondrial DNA introgression in an amphipod endemic to the ancient Lake Skadar system,Balkan Peninsula

1. Investigation of biodiversity, including genetic diversity within species, is crucial for rational planning of nature conservation and species protection. Endemics or narrow-ranged taxa, sensitive to alteration of physical and chemical conditions, may serve as local bioindicators.
2. Homoeogammarus scutarensis is an endemic, cold-adapted amphipod crustacean, inhabiting fragmented spring habitats, within a relatively small area of the Lake Skadar basin. The basin is recently under heavy anthropogenic influence leading to habitat deterioration.
3. Genetic diversity within H. scutarensis was investigated using the mitochondrial cytochrome c oxidase subunit I and the nuclear 28S ribosomal RNA markers. Genetic diversity within the mitochondrial (mt)DNA appeared to be surprisingly high as for the limited spatial scale. The history of within-species divergence dates back at least to the Pliocene.
4. A case of interspecific mtDNA introgression from the endemic H. scutarensis to the widespread and partly sympatric Homoeogammarus thoni was observed in one of the studied populations.
5. Demographic analysis showed that the demography of H. scutarensis population has been stable, without evidence of expansion. Thus, we believe that H. scutarensis, responsive to environmental changes, is a proper model mirroring the conditions in sensitive habitats of the Lake Skadar basin. To protect ongoing evolutionary processes, the conservation measures for this species should take into account the complex fine-scale lineage endemism patterns. This case study may also provide a hint for planning conservation strategies in other geologically old spring systems.
6. Most of the localities where H. scutarensis occurs provide refugia for divergent mtDNA lineages, suggesting prolonged isolation between sites and independent evolutionary histories. We conclude that H. scutarensis is composed of two or three conservation units. One of them occupies the headwaters of the Crnojevića River and spring in its valley. The other is widespread throughout the sub-lacustrine springs and the Zeta Plain; however, a group of unique haplotypes is found in springs in the Podhum Bay. Their presence and distribution should be considered while planning any investments or conservation strategies.

     

Development of endocrine pancreatic islets in embryos of the grass snake Natrix natrix (Lepidosauria,Serpentes)

Differentiation of the pancreatic islets in grass snake Natrix natrix embryos, was analyzed using light, transmission electron microscopy, and immuno-gold labeling. The study focuses on the origin of islets, mode of islet formation, and cell arrangement within islets. Two waves of pancreatic islet formation in grass snake embryos were described. The first wave begins just after egg laying when precursors of endocrine cells located within large cell agglomerates in the dorsal pancreatic bud differentiate. The large cell agglomerates were divided by mesenchymal cells thus forming the first islets. This mode of islet formation is described as fission. During the second wave of pancreatic islet formation which is related to the formation of the duct mantle, we observed four phases of islet formation: (a) differentiation of individual endocrine cells from the progenitor layer of duct walls (budding) and their incomplete delamination; (b) formation of two types of small groups of endocrine cells (A/D and B) in the wall of pancreatic ducts; (c) joining groups of cells emerging from neighboring ducts (fusion) and rearrangement of cells within islets; (d) differentiated pancreatic islets with characteristic arrangement of endocrine cells. Mature pancreatic islets of the grass snake contained mainly A endocrine cells. Single B and D or PP–cells were present at the periphery of the islets. This arrangement of endocrine cells within pancreatic islets of the grass snake differs from that reported from most others vertebrate species. Endocrine cells in the pancreas of grass snake embryos were also present in the walls of intralobular and intercalated ducts. At hatching, some endocrine cells were in contact with the lumen of the pancreatic ducts.     

The Proteomic Landscape of Centromeric Chromatin Reveals an Essential Role for the Ctf19CCAN Complex in Meiotic Kinetochore Assembly

1. Download : Download high-res image (163KB)
2. Download : Download full-size image

     

How does metal soil pollution change the plant mycobiome?

Microorganisms play a key role in plant adaptation to the environment. The aim of this study was to evaluate the effect of toxic metals present in the soil on the biodiversity of plant-related, endophytic mycobiota. The mycobiome of plants and soil from a Zn–Pb heap and a metal-free ruderal area were compared via Illumina sequencing of the ITS1 rDNA. The biodiversity of plants and fungi inhabiting mine dump substrate was lower than that of the metal free site. In the endosphere of Arabidopsis arenosa from the mine dump the number of endophytic fungal taxa was comparable to that in the reference population, but the community structure significantly differed. Agaricomycetes was the most notably limited class of fungi. The results of plant mycobiota evaluation from the field study were verified in terms of the role of toxic metals in plant endophytic fungi community assembly in a reconstruction experiment. The results presented in this study indicate that metal toxicity affects the structure of the plant mycobiota not by changing the pool of microorganisms available in the soil from which the fungal symbionts are recruited but most likely by altering plant and fungi behaviour and the organisms' preferences towards associating in symbiotic relationships.