The nature of plant adaptations to salinity stress has trophic consequences

In different ecosystems herbivores highly prefer particular plant species. This is often explained in a stoichiometric framework of nutrient‐based plant adaptations to herbivory. We hypothesize that such super‐palatability can also arise as an evolutionary by‐product of osmoregulatory adaptations of plants to stressful environmental conditions, as salinity, drought and cold. Here, we investigate in a coastal salt marsh why some plant species are highly preferred by migratory brent geese Branta bernicla bernicla in spring while others are avoided. This salt marsh is an important spring staging site for the geese. Sufficient energy storage in a short period is critical to enable their northward migration to Siberia and subsequent reproduction. We test if geese prefer plants that balance their internal osmotic potential with the saline environment through energy‐rich soluble sugars over plant species that use (compartmentalized) salts for this. We find that plant nitrogen and acid detergent fiber content, classic predictors of herbivore preferences, poorly explain which plants the geese prefer. Instead, plant species that are highly preferred by the geese adapt to salinity by high soluble sugar concentrations while avoided species do this by high plant salt concentrations. Thus, the type of osmoregulatory adaptation to stress displayed by different plant species is a good predictor for the food preference of geese on this salt marsh. We suggest that variation in other types of osmoregulation‐based stress adaptations, as plant cold adaptations in tundras and plant drought adaptations in savannas, have similar important consequences for trophic interactions.     

Effect of experimental gingivitis induction and erythritol on the salivary metabolome and functional biochemistry of systemically healthy young adults

Introduction

Understanding the changes occurring in the oral ecosystem during development of gingivitis could help improve prevention and treatment strategies for oral health. Erythritol is a non-caloric polyol proposed to have beneficial effects on oral health.

Objectives

To examine the effect of experimental gingivitis and the effect of erythritol on the salivary metabolome and salivary functional biochemistry.

Methods

In a two-week experimental gingivitis challenge intervention study, non-targeted, mass spectrometry-based metabolomic profiling was performed on saliva samples from 61 healthy adults, collected at five time-points. The effect of erythritol was studied in a randomized, controlled trial setting. Fourteen salivary biochemistry variables were measured with antibody- or enzymatic activity-based assays.

Results

Bacterial amino acid catabolites (cadaverine, N-acetylcadaverine, and α-hydroxyisovalerate) and end-products of bacterial alkali-producing pathways (N-α-acetylornithine and γ-aminobutyrate) increased significantly during the experimental gingivitis. Significant changes were found in a set of 13 salivary metabolite ratios composed of host cell membrane lipids involved in cell signaling, host responses to bacteria, and defense against free radicals. An increase in mevalonate was also observed. There were no significant effects of erythritol. No significant changes were found in functional salivary biochemistry.

Conclusions

The findings underline a dynamic interaction between the host and the oral microbial biofilm during an experimental induction of gingivitis.

     

Breaking the state of the heart: meshless model for cardiac mechanics

Biomechanics and Modeling in Mechanobiology - Cardiac modeling has recently emerged as a promising tool to study pathophysiology mechanisms and to predict treatment outcomes for personalized...     

Archaic and contemporary topographic diversification of Upper Mississippi River forests

Topographic diversity is an important component of environmental heterogeneity. Topographic diversity within the Upper Mississippi River floodplain has been degraded because of modifications for navigation improvement. Efforts aimed at restoring topographic diversity in the Upper Mississippi River floodplain have been extensive but have not focused on reversing the effects of forest loss and degradation. We investigated habitat features associated with Cerulean Warbler (Setophaga cerulea) locations both within and outside of river floodplains and hypothesized this species would select topographically diverse habitats. Both topographic diversity and the distance to the upland forest/floodplain forest interface were useful predictors of Cerulean Warbler presence. We conclude that incorporation of topographic diversity into floodplain forest restoration planning would likely benefit Cerulean Warblers and the other species with similar habitat requirements. Incorporating topographic diversity into floodplain forest conservation planning will be challenging on major rivers that serve multiple purposes.     

FXR-deficiency confers increased susceptibility to torpor

The role of the nuclear receptor FXR in adaptive thermogenesis was investigated using FXR-deficient mice. Despite elevated serum bile acid concentrations and increased mRNA expression profiles of thermogenic genes in brown adipose tissue, FXR-deficiency did not alter energy expenditure under basal conditions. However, FXR-deficiency accelerated the fasting-induced entry into torpor in a leptin-dependent manner. FXR-deficient mice were also extremely cold-intolerant. These altered responses may be linked to a more rapid decrease in plasma concentrations of metabolic fuels (glucose, triglycerides) thus impairing uncoupling protein 1-driven thermogenesis. These results identify FXR as a modulator of energy homeostasis.     

A kinetic approach to the dependence of dissimilatory metal reduction by Shewanella oneidensis MR-1 on the outer membrane cytochromes c OmcA and OmcB

The Gram-negative bacterium Shewanella oneidensis MR-1 shows a remarkably versatile anaerobic respiratory metabolism. One of its hallmarks is its ability to grow and survive through the reduction of metallic compounds. Among other proteins, outer membrane decaheme cytochromes c OmcA and OmcB have been identified as key players in metal reduction. In fact, both of these cytochromes have been proposed to be terminal Fe(III) and Mn(IV) reductases, although their role in the reduction of other metals is less well understood. To obtain more insight into this, we constructed and analyzed omcA, omcB and omcA/omcB insertion mutants of S. oneidensis MR-1. Anaerobic growth on Fe(III), V(V), Se(VI) and U(VI) revealed a requirement for both OmcA and OmcB in Fe(III) reduction, a redundant function in V(V) reduction, and no apparent involvement in Se(VI) and U(VI) reduction. Growth of the omcB(-) mutant on Fe(III) was more affected than growth of the omcA(-) mutant, suggesting OmcB to be the principal Fe(III) reductase. This result was corroborated through the examination of whole cell kinetics of OmcA- and OmcB-dependent Fe(III)-nitrilotriacetic acid reduction, showing that OmcB is approximately 11.5 and approximately 6.3 times faster than OmcA at saturating and low nonsaturating concentrations of Fe(III)-nitrilotriacetic acid, respectively, whereas the omcA(-) omcB(-) double mutant was devoid of Fe(III)-nitrilotriacetic acid reduction activity. These experiments reveal, for the first time, that OmcA and OmcB are the sole terminal Fe(III) reductases present in S. oneidensis MR-1. Kinetic inhibition experiments further revealed vanadate (V(2)O(5)) to be a competitive and mixed-type inhibitor of OmcA and OmcB, respectively, showing similar affinities relative to Fe(III)-nitrilotriacetic acid. Neither sodium selenate nor uranyl acetate were found to inhibit OmcA- and OmcB-dependent Fe(III)-nitrilotriacetic acid reduction. Taken together with our growth experiments, this suggests that proteins other than OmcA and OmcB play key roles in anaerobic Se(VI) and U(VI) respiration.