Campylobacter jejuni Motility Is Required for Infection of the Flagellotropic Bacteriophage F341

Previous studies have identified a specific modification of the capsular polysaccharide as receptor for phages that infect Campylobacter jejuni. Using acapsular kpsM mutants of C. jejuni strains NCTC11168 and NCTC12658, we found that bacteriophage F341 infects C. jejuni independently of the capsule. In contrast, phage F341 does not infect C. jejuni NCTC11168 mutants that either lack the flagellar filaments (ΔflaAB) or that have paralyzed, i.e., nonrotating, flagella (ΔmotA and ΔflgP). Complementing flgP confirmed that phage F341 requires rotating flagella for successful infection. Furthermore, adsorption assays demonstrated that phage F341 does not adsorb to these nonmotile C. jejuni NCTC11168 mutants. Taken together, we propose that phage F341 uses the flagellum as a receptor. Phage-host interactions were investigated using fluorescence confocal and transmission electron microscopy. These data demonstrate that F341 binds to the flagellum by perpendicular attachment with visible phage tail fibers interacting directly with the flagellum. Our data are consistent with the movement of the C. jejuni flagellum being required for F341 to travel along the filament to reach the basal body of the bacterium. The initial binding to the flagellum may cause a conformational change of the phage tail that enables DNA injection after binding to a secondary receptor.     

Past and future range shifts and loss of diversity in dwarf willow (Salix herbacea L.) inferred from genetics, fossils and modelling

Aim Climate change may cause loss of genetic diversity. Here we explore how a multidisciplinary approach can be used to infer effects of past climate change on species distribution and genetic diversity and also to predict loss of diversity due to future climate change. We use the arctic‐alpine plant Salix herbacea L. as a model. Location Europe, Greenland and eastern North America. Methods We analysed 399 samples from 41 populations for amplified fragment length polymorphism (AFLP) to identify current patterns of genetic structure and diversity and likely historical dispersal routes. Macrofossil records were compiled to infer past distribution, and species distribution models were used to predict the Last Glacial Maximum (LGM) and future distribution of climatically suitable areas. Results We found strong genetic differentiation between the populations from Europe/East Greenland and those from Canada/West Greenland, indicating a split probably predating the LGM. Much less differentiation was observed among the four genetic groups identified in Europe, and diversity was high in the Scandinavian as well as in southern alpine populations. Continuous distribution in Central Europe during the last glaciation was inferred based on the fossil records and distribution modelling. A 46–57% reduction in suitable areas was predicted in 2080 compared to present. However, mainly southern alpine populations may go extinct, causing a loss of about 5% of the genetic diversity in the species. Main conclusions From a continuous range in Central Europe during the last glaciation, northward colonization probably occurred as a broad front maintaining diversity as the climate warmed. This explains why potential extinction of southern populations by 2080 will cause a comparatively low loss of the genetic diversity in S. herbacea. For other species with different glacial histories, however, the expected climate‐change induced regional extinction may cause a more severe loss of genetic diversity. We conclude that our multidisciplinary approach may be a useful tool for assessing impact of climate change on loss of genetic diversity.     

Facial Displays in Cebus apella

Tufted capuchins are diurnal New World primates whose social interactions involve vocal and visual communication. We aimed to describe their facial displays and assessed the use (in relation to rank and age/sex classes of the sender or the receiver or both) and the social function of the most frequent ones. More specifically, we analyzed the temporal relationship between each facial display and specific classes of behaviors, e.g., play, aggression, performed by the sender and by the receiver (Pre-Post-Event Histogram [PPEH]). We observed 20 captives, belonging to 2 groups, for a total of 320 h. The capuchins displayed relaxed open-mouth, silent bared-teeth, open-mouth threat, lip-smacking, open-mouth silent bared-teeth, scalp lifting, and, rarely, protruded lips. The repertoire and the meanings of the different facial expressions are similar to those described for Catarrhini. In some cases, such as for the silent bared-teeth display, the meaning depends on the age of the sender. Silent bared-teeth is associated with play in juveniles and with submissiveness of the sender to the receiver and affiliative interactions in adults. The finding, and the fact that silent bared-teeth display is used during courtship (Carosi and Visalberghi, 2002), support Preuschoft and van Hooff’s (1995, 1997) power asymmetry hypothesis of motivational emancipation, according to which there is convergence between affiliative and submissive behaviors in species with a high degree of social tolerance.     

Evidence for a pre-latent form of the serpin plasminogen activator inhibitor-1 with a detached beta-strand 1C

Latency transition of plasminogen activator inhibitor-1 (PAI-1) occurs spontaneously in the absence of proteases and results in stabilization of the molecule through insertion of its reactive center loop (RCL) as a strand in beta-sheet A and detachment of beta-strand 1C (s1C) at the C-terminal hinge of the RCL. This is one of the largest structural rearrangements known for a folded protein domain without a concomitant change in covalent structure. Yet, the sequence of conformational changes during latency transition remains largely unknown. We have now mapped the epitope for the monoclonal antibody H4B3 to the cleft revealed upon s1C detachment and shown that H4B3 inactivates recombinant PAI-1 in a time-dependent manner. With fluorescence spectroscopy, we show that insertion of the RCL is accelerated in the presence of H4B3, demonstrating that the loss of activity is the result of latency transition. Considering that the epitope for H4B3 appears to be occluded by s1C in active PAI-1, this finding suggests the existence of a pre-latent conformation on the path from active to latent PAI-1 characterized by at least partial detachment of s1C. Functional characterization of mutated PAI-1 variants suggests that a salt-bridge between Arg273 and Asp224 may stabilize the pre-latent conformation. The binding of H4B3 and of a peptide targeting the cleft revealed upon s1C detachment was hindered by the glycans attached to Asn267. Conclusively, we have provided evidence for the existence of an equilibrium between active PAI-1 and a pre-latent form, characterized by reversible detachment of s1C and formation of a glycan-shielded cleft in the molecule.     

Geographical and environmental controls of palm beta diversity in paleo-riverine terrace forests in Amazonian Peru

The palm (Arecaceae) community on low paleo-riverine terraces (terrace forest) in the north-western Amazon, is described, and we assessed the importance of environmental differences and geographic distance as drivers of its local (25² grain and 0–500 extent) and regional scale (500² grain and 0.3–143 km extent) beta diversity using ordination, multiple regressions on distance matrices and Indicator Species Analysis. A total of 15,869 individuals and 37 species of palm were sampled in 10 terrace forest transects, while 3758 individuals and 21 species were sampled in two adjacent floodplain forest transects for comparison. The terrace and floodplain forest were clearly different in their diversity and floristic composition. The relative importance of geographical distance and environmental difference as controls of terrace forest beta diversity was scale dependent, with environmental differences, notably in soil moisture, dominating at local scales and geographical distance dominating at regional scales. In fact, none of the environmental factors had a significant influence on regional-scale beta diversity. The geographical distance decay in floristic similarity was markedly steeper at local scale ( −0.25 km ⁻¹) than at regional scale ( −0.003 km⁻¹). Such a nonlinear decay is expected if simple dispersal limitation controls beta diversity. However, the absent flattening of the distance decay at the largest distances and the sub-Andean affinities of the westernmost palm communities suggest that large-scale biogeographical processes also contribute to the regional-scale beta diversity. Hereby our results indicate that not only local environment, but also dispersal limitation and biogeographical history can be important controls of the diversity and composition of local plant communities.     

Investigation of oxidation in freeze-dried membranes using the fluorescent probe C11-BODIPY

Incorporation of the fluorescent probe C11-BODIPY^581/591 in two dried membrane systems, soy bean phosphatidylcholine liposomes freeze-dried in a carbohydrate/protein matrix and Lactobacillus acidophilus (La-5) freeze-dried in a carbohydrate matrix, was successful and could be visualised by Confocal Laser Scanning Microscopy (CLSM). The C11-BODIPY^581/591 probe is a lipid oxidation reporter molecule, which is known to associate with the lipids of biological membranes and exhibit a fluorescence shift from the red range to the green range of the visible spectrum when it is oxidised together with the lipids. The present study is the first to demonstrate that the C11-BODIPY^581/591 probe can be used in dried membrane systems, and that a detection of oxidation is possible by CLSM analysis directly on the dried samples.     

On the Thermodynamic Efficiency of Ca2+-ATPase Molecular Machines

Experimental studies have shown that the activity of the reconstituted molecular pump Ca²⁺-ATPase strongly depends on the thickness of the supporting bilayer. It is thus expected that the bilayer structure will have an impact on the thermodynamic efficiency of this nanomachine. Here, we introduce a nonequilibrium-thermodynamics theoretical approach to estimate the thermodynamic efficiency of the Ca²⁺-ATPase from analysis of available experimental data about ATP hydrolysis and Ca²⁺ transport. We find that the entropy production, i.e., the heat released to the surroundings under working conditions, is approximately constant for bilayers containing phospholipids with hydrocarbon chains of 18–22 carbon atoms. Our estimates for the heat released during the pump operation agree with results obtained from separate calorimetric experiments on the Ca²⁺-ATPase derived from sarcoplasmic reticulum. We show that the thermodynamic efficiency of the reconstituted Ca²⁺-ATPase reaches a maximum for bilayer thicknesses corresponding to maximum activity. Surprisingly, the estimated thermodynamic efficiency is very low, ～12%. We discuss the significance of this result as representative of the efficiency of other nanomachines, and we address the influence of the experimental set-up on such a low efficiency. Overall, our approach provides a general route to estimate thermodynamic efficiencies and heat dissipation in experimental studies of nanomachines.