Co-limitation towards lower latitudes shapes global forest diversity gradients

The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers.

Arthropod dark taxa provide new insights into diversity responses to bark beetle infestations

Natural disturbances are increasing around the globe, also impacting protected areas. Although previous studies have indicated that natural disturbances result in mainly positive effects on biodiversity, these analyses mostly focused on a few well established taxonomic groups, and thus uncertainty remains regarding the comprehensive impact of natural disturbances on biodiversity. Using Malaise traps and meta-barcoding, we studied a broad range of arthropod taxa, including dark and cryptic taxa, along a gradient of bark beetle disturbance severities in five European national parks. We identified order-level community thresholds of disturbance severity and classified barcode index numbers (BINs; a cluster system for DNA sequences, where each cluster corresponds to a species) as negative or positive disturbance indicators. Negative indicator BINs decreased above thresholds of low to medium disturbance severity (20%-30% of trees killed), whereas positive indicator BINs benefited from high disturbance severity (76%-98%). BINs allocated to a species name contained nearly as many positive as negative disturbance indicators, but dark and cryptic taxa, particularly Diptera and Hymenoptera in our data, contained higher numbers of negative disturbance indicator BINs. Analyses of changes in the richness of BINs showed variable responses of arthropods to disturbance severity at lower taxonomic levels, whereas no significant signal was detected at the order level due to the compensatory responses of the underlying taxa. We conclude that the analyses of dark taxa can offer new insights into biodiversity responses to disturbances. Our results suggest considerable potential for forest management to foster arthropod diversity, for example by maintaining both closed-canopy forests (>70% cover) and open forests (<30% cover) on the landscape.

Specialisation and diversity of multiple trophic groups are promoted by different forest features

While forest management strongly influences biodiversity, it remains unclear how the structural and compositional changes caused by management affect different community dimensions (e.g. richness, specialisation, abundance or completeness) and how this differs between taxa. We assessed the effects of nine forest features (representing stand structure, heterogeneity and tree composition) on thirteen above- and belowground trophic groups of plants, animals, fungi and bacteria in 150 temperate forest plots differing in their management type. Canopy cover decreased light resources, which increased community specialisation but reduced overall diversity and abundance. Features increasing resource types and diversifying microhabitats (admixing of oaks and conifers) were important and mostly affected richness. Belowground groups responded differently to those aboveground and had weaker responses to most forest features. Our results show that we need to consider forest features rather than broad management types and highlight the importance of considering several groups and community dimensions to better inform conservation.

Heterotrimeric collagen peptides as fluorogenic collagenase substrates: synthesis, conformational properties, and enzymatic digestion

The collagenase cleavage site of collagen type I, i.e., the sequence portions 772-784 (P(4)-P(9)') and 772-785 (P(4)-P(10)') of the two alpha1-chains and the sequence portion 772-784 (P(4)-P(9)') of the alpha2-chain, were assembled in an alpha1alpha2alpha1' register by C-terminal cross-linking of these peptides with an artificial cystine knot. The triple-helical conformation of the construct was stabilized by N-terminal extensions with (Gly-Pro-Hyp)(5) repeats. The gaps in the sequence alignment were filled up, and the alpha1-chain was dansylated and the alpha1'-chain was acylated with a tryptophan residue to place in spatial proximity the two chromophores for an efficient fluorescence resonance energy transfer. Although the incorporation of the two N-terminal chromophores leads to partial destabilization of the overall triple-helical fold, the heterotrimer behaved as a collagen-like substrate of the matrix metalloproteinases MMP-1 and MMP-13. Cleavage of the fluorogenic heterotrimer leads to a 6-fold increase in fluorescence intensity, thus making it a useful fluorogenic substrate for interstitial collagenases. With this folded heterotrimeric collagen molecule it was shown that fluorescence resonance energy transfer, as applied so far only for the design of linear fluorogenic enzyme substrates, can also be exploited in conformation dependency.

Decreased soluble adhesion molecule L-selectin plasma concentrations after major trauma

BACKGROUND

Binding of the leukocyte glycoprotein L-selectin to ligands expressed by activated endothelium directs leukocyte recruitment to areas of acute inflammation. Sequestration by activated microvascular endothelium has been proposed to explain the low plasma concentrations of soluble L-selectin (sCD62L) observed early in patients with acute respiratory distress syndrome. We hypothesized that inflammatory endothelial activation may occur in trauma patients, leading to decreased sCD62L plasma concentrations.

METHODS

This study was a prospective analysis of sCD62L plasma concentrations in patients with isolated head injuries and multiple trauma patients without head injuries admitted to two tertiary-level intensive care units. sCD62L plasma concentrations were determined in 18 consecutive adult patients with isolated moderate and severe head injuries and in 13 multiple trauma patients without head injuries immediately upon admission to the intensive care unit and then daily for up to 10 days after trauma.

RESULTS

Compared with healthy adult controls (n=22), patient sCD62L plasma concentrations were significantly decreased upon admission (5.7+/-1.6 vs. 11.0+/-1.7 pmol/mL; p < 0.001). In all patients, sCD62L concentrations remained depressed throughout the study period. sCD62L concentrations did not differ significantly between patients with isolated head injuries and multiple trauma patients without head injuries, although repeated-measures analysis of variance showed significantly more depressed sCD62L concentrations associated with severe (n=14) compared with moderate head injuries (n=4) during the study period (p < 0.05).

CONCLUSION

Patients with major trauma present with a significant reduction of sCD62L plasma concentrations within the first 12 hours after trauma and during subsequent intensive care. This finding suggests widespread microvascular endothelial activation after trauma, which may be associated with increased neutrophil extravasation.

Non-peptidic cysteine derivatives as inhibitors of matrix metalloproteinases

By exploiting the thiol function of L-cysteine as a chelating group of the active-site zinc atom of matrix metalloproteinases (MMPs), N- and C-terminal derivatization of this amino acid with aliphatic and aromatic groups allowed us to explore the selectivity of the S and/or S' binding subsites of human neutrophil collagenase (MMP8) and stromelysin (MMP3). With N-benzyloxycarbonyl-L-cysteine-(2-phenyl)ethylamide a submicromolar inhibitor of MMP8 was discovered.

Ro 22-5417, a new clavam antibiotic from Streptomyces clavuligerus. III. Absolute stereochemistry

The complete stereostructure of the new antibiotic Ro 22-5417 has been established as 3-[(3S,5S)-7-oxo-1-aza-4-oxabicyclo[3.2.O]hept-3-yl]-L-alanine. This result together with the synthesis of an (3R,5R)-L-analog allowed us to postulate that clavams require the R-configuration at the ring juncture for beta-lactamase inhibitory activity, while the opposite S-stereochemistry is essential for antifungal activity.