Alterins Produced by Oyster-Associated Pseudoalteromonas Are Antibacterial Cyclolipopeptides with LPS-Binding Activity

Discovery after discovery, host-associated microbiota reveal a growing list of positive effects on host homeostasis by contributing to host nutrition, improving hosts’ immune systems and protecting hosts against pathogens. In that context, a collection of oyster associated bacteria producing antibacterial compounds have been established to evaluate their role in non-host-derived immunity. Here, we described alterins; potent anti-Gram negative compounds produced by Pseudoalteromonas hCg-6 and hCg-42 isolated from different healthy oyster hemolymph. The strains hCg-6 and hCg-42 produce a set of at least seven antibacterial compounds, ranging from 926 to 982 Da structurally characterized as cyclolipopeptides (CLPs). Alterins share the same cationic heptapeptidic cycle connected via an amido bond to different hydrophobic hydrocarbon tails. Their MICs disclosed a potent antibacterial activity directed against Gram-negative bacteria including oyster and human pathogens that may confer a beneficial defense mechanism to the host but also represents an untapped source of new antibiotics. The alterins’ mechanisms of action have been deciphered: after binding to lipopolysaccharides (LPS), alterins provoke a membrane depolarization and permeabilization leading to bacterial lysis. As hCg-6 and hCg-42 produced a set of natural derivatives, the structure/activity relationship linked to the carbon tail is clarified. We showed that the hydrocarbon tail determines the LPS-binding properties of alterins and consequently their antibacterial activities. Its length and saturation seem to play a major role in this interaction.     

Intra- and inter-provenance variability in phloem phenols of Picea abies and relationship to a bark beetle-associated fungus

One hundred Norway spruce (Picea abies (L.) Karst.) clones (three ramets per clone) were analyzed for phloem phenol composition and concentration before and 10 days after wound inoculation with sterile malt agar. Fifty clones (Experiment 1) belonged to the same provenance, whereas the remaining clones (Experiment 2) belonged to five provenances from three geographic areas. In Experiment 2, two additional ramets from the same clones were mass inoculated with Ceratocystis polonica (Siem.) C. Moreau to quantify the resistance of each clone. Tree response to wound inoculations was characterized by increased catechin concentration in both experiments, accompanied by increases in astringin and decreases in piceid in Experiment 1. In both experiments, we observed a diverse group of phenolic compounds whose concentrations increased (catechin, astringin) or did not vary (taxifolin glucoside) in response to wound inoculations, whereas concentrations of a homogeneous group of stilbene compounds decreased (piceid) or did not vary (isorhapontin, unidentified stilbene). In Experiment 2, provenances from the alpine and Hercynian-Carpatic areas differed from provenances from the Baltic area with respect to the relative importance of these two groups of compounds, further indicating that the two groupings of phenolic compounds structure the Norway spruce populations. Eighty days after mass inoculation, the percentage of healthy sapwood, which was taken as a measure of tree resistance, indicated that clones from the Baltic area were less resistant to mass inoculations than clones from the alpine and Hercynian-Carpatic areas. We conclude that the degree of resistance of Norway spruce trees to mass inoculations with a bark beetle-associated fungus can be predicted based on the diversity of constitutive phloem phenols and the ability to induce phenol synthesis in response to wounding.     

Dietary iron-initiated lipid oxidation and its inhibition by polyphenols in gastric conditions

The gastric tract may be the first site where food is exposed to postprandial oxidative stress and antioxidant activity by plant micronutrients. After food intake, dietary iron, dioxygen, and emulsified lipids come into close contact and lipid oxidation may take place. This study investigated lipid oxidation and its inhibition by dietary polyphenols in gastric-like conditions. Lipid oxidation induced by heme and nonheme iron was studied in acidic sunflower oil-in-water emulsions. The emulsifier type (bovine serum albumin, phospholipids), pH, and iron form were found to be factors governing the oxidation rates. Quercetin, rutin, and chlorogenic acid highly inhibited the metmyoglobin-initiated lipid oxidation in both emulsified systems at pH 5.8. Additionally, quercetin inhibited nonheme iron-initiated processes, while it was inefficient with hematin as an initiator. The presence of human gastric juice did not influence lipid oxidation, although it diminished the antioxidant activity of phenolics. Model emulsions may thus be valuable tools to study the gastric stability of polyunsaturated lipids.     

Integrating landscape ecology and conservation physiology

The need to understand how anthropogenic landscape alteration affects fauna populations has never been more pressing. The importance of developing an understanding of the processes behind local extinction is widely acknowledged, but inference from spatial patterns of fauna distribution continues to dominate. However, this approach is limited in its ability to generate strong predictions about future distributions and local extinctions, especially when population-level responses to landscape alteration are subject to long time lags. We review the potential for indices of physiological stress and condition to contribute to understanding of how landscape pattern affects species persistence. Such measures can indicate habitat quality from the perspective of the individual animal, and can reveal environmental stressors before their negative consequences begin to manifest at a population level. Spatial patterns of chronic stress may therefore yield valuable insight into how landscape alteration influences species. We propose that the emerging disciplines of conservation physiology and macrophysiology have much to offer spatial ecology, and have great potential to reveal the physiological pathways through which habitat alteration affects fauna populations and their persistence in fragmented landscapes.     

Correlations and variance among species traits explain contrasting impacts of fragmentation and habitat loss on functional diversity

Landscape Ecology - Understanding how landscape fragmentation affects functional diversity, defined as the distribution of functional traits in an assemblage, is critical for managing landscapes...     

Immune response following vaccination against Salmonella Enteritidis using 2 commercial bacterins in laying hens

The humoral and cell-mediated immune (CMI) response to 2 commercial killed Salmonella Enteritidis (SE) vaccines (Layermune and MBL SE4C) was evaluated in laying hens. Layers were distributed in 2 experimental groups. The first received a single immunization at 16 wk of age, while the second experimental group was immunized at 12 wk of age and again at 18 wk of age. Serum immunoglobulin (Ig)G antibodies were measured using a commercial SE ELISA kit and showed persistent levels from 3 to 32 and 34 wk post-vaccination. The vaccination protocol using 2 immunizations showed a higher seroconversion level than the single vaccination. However, our results for bacterial intracellular survival indicated that IgG titers were not linked with bacterial killing. Local IgA production was measured in the intestines and oviducts with an in-house SE whole cell antigen ELISA. Only the MBL SE4C vaccine elicited IgA antibody production when tested on intestine and oviduct mucosal secretions, 3-weeks post-vaccination in both immunization protocol groups. To evaluate the CMI response, the splenic T-cells and B-cells populations were analyzed using flow cytometry. The CD3/B-cell ratio decreased 3 wk after the second immunization in the twice vaccinated Layermune group due to an increase in B-cells.     

Understanding Ebola virus and other zoonotic transmission risks through human–bat contacts: Exploratory study on knowledge,attitudes and practices in Southern Cameroon

The ecology of Ebola virus (EBV) remains largely unknown, but the previous detection of viral RNA and anti‐EBV antibodies in African bats suggests that they might play a role in the EBV reservoir. Moreover, African bats also carry other potentially zoonotic agents such as Henipah‐like viruses, coronaviruses and lyssaviruses. Today only little information is available on interactions between humans and bats. The objective of our exploratory study was to describe the extent and modes of contacts between humans and bats in southern Cameroon, considered as an area at risk for future EBV outbreaks. The survey was conducted in 11 villages of four distinct rural areas in southern Cameroon. A total of 135 respondents were interviewed using semi‐structured questionnaires, between February and May 2017. The study showed that direct contacts between bats and humans are relatively common. Bat bushmeat appeared to be an occasional meat resource; 40% of respondents consume bats with a median annual consumption of three, and 28% of respondents hunt them. About 22% of the respondents reported children catching bats. Indirect contact also appeared to be common; 55% of hunters use caves as shelters and 67% of interviewees eat fruits previously chewed by bats. Bat consumption varied significantly between regions (from 0% to 87%) and between pygmies and bantus in the extreme south‐east of Cameroon. The study revealed considerable diversity in practices among interviewees, most of them being subsistence cultivators and relying on self‐hunted bushmeat. Geographical diversity of contacts and perceptions regarding bats in Cameroon emphasizes the need to adjust zoonotic pathogen surveillance and education campaigns to the specificities of the communities and their context of interaction with wildlife.     

Genetic engineering of plant volatile terpenoids: effects on a herbivore,a predator and a parasitoid

BACKGROUND: Most insect‐resistant transgenic crops employ toxins to control pests. A novel approach is to enhance the effectiveness of natural enemies by genetic engineering of the biosynthesis of volatile organic compounds (VOCs). Before the commercialisation of such transgenic plants can be pursued, detailed fundamental studies of their effects on herbivores and their natural enemies are necessary. The linalool/nerolidol synthase gene FaNES1 was constitutively expressed from strawberry in three Arabidopsis thaliana accessions, and the behaviour of the aphid Brevicoryne brassicae L., the parasitoid Diaeretiella rapae McIntosh and the predator Episyrphus balteatus de Geer was studied. RESULTS: Transgenic FaNES1‐expressing plants emitted (E)‐nerolidol and larger amounts of (E)‐DMNT and linalool. Brevicoryne brassicae was repelled by the transgenic lines of two of the accessions, whereas its performance was not affected. Diaeretiella rapae preferred aphid‐infested transgenic plants over aphid‐infested wild‐type plants for two of the accessions. In contrast, female E. balteatus predators did not differentiate between aphid‐infested transgenic or wild‐type plants. CONCLUSION: The results indicate that the genetic engineering of plants to modify their emission of VOCs holds considerable promise for facilitating biological control of herbivores. Validation for crop plants is a necessary next step to assess the usefulness of modified volatile emission in integrated pest management. Copyright © 2012 Society of Chemical Industry