Structural-Functional Studies of Burkholderia cenocepacia D-Glycero-beta-D-manno-heptose 7-Phosphate Kinase (HldA) and Characterization of Inhibitors with Antibiotic Adjuvant and Antivirulence Properties

As an essential constituent of the outer membrane of Gram-negative bacteria, lipopolysaccharide contributes significantly to virulence and antibiotic resistance. The lipopolysaccharide biosynthetic pathway therefore serves as a promising therapeutic target for antivirulence drugs and antibiotic adjuvants. Here we report the structural-functional studies of D-glycero-beta-D-manno-heptose 7-phosphate kinase (HldA), an absolutely conserved enzyme in this pathway, from Burkholderia cenocepacia. HldA is structurally similar to members of the PfkB carbohydrate kinase family and appears to catalyze heptose phosphorylation via an in-line mechanism mediated mainly by a conserved aspartate, Asp270. Moreover, we report the structures of HldA in complex with two potent inhibitors in which both inhibitors adopt a folded conformation and occupy the nucleotide-binding sites. Together, these results provide important insight into the mechanism of HldA-catalyzed heptose phosphorylation and necessary information for further development of HldA inhibitors.

Lactobacillus strains isolated from infant faeces possess potent inhibitory activity against intestinal alpha- and beta-glucosidases suggesting anti-diabetic potential

Purpose: Inhibitors of intestinal alpha-glucosidases are used therapeutically to treat type 2 diabetes mellitus. Bacteria such as Actinoplanes sp. naturally produce potent alpha-glucosidase inhibitor compounds, including the most widely available drug acarbose. It is not known whether lactic acid bacteria (LAB) colonising the human gut possess inhibitory potential against glucosidases. Hence, the study was undertaken to screen LABs having inherent alpha- and beta-glucosidase inhibitory potential. Methods: This study isolated, screened, identified and extracted Lactobacillus strains (Lb1–15) from human infant faecal samples determining their inhibitory activity against intestinal maltase, sucrase, lactase and amylase. Lactobacillus reference strains (Ref1–7), a Gram positive control (Ctrl1) and two Gram negative controls (Ctrl2–3), were also analysed to compare activity. Results: Faecal isolates were identified by DNA sequencing, with the majority identified as unique strains of Lactobacillus plantarum. Some strains (L. plantarum, L. fermentum, L. casei and L. rhamnosus) had potent and broad spectrum inhibitory activities (up to 89 %; p < 0.001; 500 mg/ml wet weight) comparable to acarbose (up to 88 %; p < 0.001; 30 mg/ml). Inhibitory activity was concentration-dependent and was freely available in the supernatant, and was not present in other bacterial genera (Bifidobacterium bifidum and Escherichia coli or Salmonella typhimurium). Interestingly, the potency and spectrum of inhibitory activity across strains of a single species (L. plantarum) differed substantially. Some Lactobacillus extracts had broader spectrum activities than acarbose, effectively inhibiting beta-glucosidase activity (lactase) as well as alpha-glucosidase activities (maltase, sucrase and amylase). Anti-diabetic potential was indicated by the fact that oral gavage with a L. rhamnosus extract (1 g/kg) was able to reduce glucose excursions (Area under curve; 22 %; p < 0.05) in rats during a carbohydrate challenge (starch; 2 g/kg). Conclusion: These results definitively demonstrate that Lactobacillus strains present in the human gut have alpha- and beta-glucosidase inhibitory activities and can reduce blood glucose responses in vivo. Although the potential use of LAB such as Lactobacillus as a dietary supplement, medicinal food or biotherapeutic for diabetes is uncertain, such an approach might offer advantages over drug therapies in terms of broader spectrum activities and fewer unpleasant side effects. Further characterisation of this bioactivity is warranted, and chronic studies should be undertaken in appropriate animal models or diabetic subjects.

The Beta Agonist Lung Injury Trial Prevention:A Randomized Controlled Trial

Rationale: Experimental studies suggest that pretreatment with b-agonists might prevent acute lung injury (ALI).

Objectives: To determine if in adult patients undergoing elective esophagectomy, perioperative treatment with inhaled b-agonists effects the development of early ALI.

Methods:We conducted a randomized placebo-controlled trial in 12 UK centers (2008-2011). Adult patients undergoing elective esophagectomy were allocated to prerandomized, sequentially numbered treatment packs containing inhaled salmeterol (100 mg twice daily) or a matching placebo. Patients, clinicians, and researchers were masked to treatment allocation. The primary outcome was development of ALI within 72 hours of surgery. Secondary outcomes were ALI within 28 days, organ failure, adverse events, survival, and health-related quality of life. An exploratory substudy measured biomarkers of alveolar-capillary inflammation and injury.

Measurements and Main Results: A total of 179 patients were randomized to salmeterol and 183 to placebo. Baseline characteristics were similar. Treatment with salmeterol did not prevent early lung injury (32 [19.2%] of 168 vs. 27 [16.0%] of 170; odds ratio [OR], 1.25; 95% confidence interval [CI], 0.71-2.22). There was no difference in organ failure, survival, or health-related quality of life.Adverse events were less frequent in the salmeterol group (55 vs. 70; OR, 0.63; 95% CI, 0.39-0.99), predominantly because of a lower number of pneumonia (7 vs. 17; OR, 0.39; 95% CI, 0.16-0.96). Salmeterol reduced some biomarkers of alveolar inflammation and epithelial injury.

Conclusion: Perioperative treatment with inhaled salmeterol was well tolerated but did not prevent ALI.

Clinical trial registered with International Standard Randomized Controlled Trial Register (ISRCTN47481946) and European Union database of randomized Controlled Trials (EudraCT 2007-004096-19).Copyright © 2014 by the American Thoracic Society.

Disturbance, neutral theory and patterns of beta diversity in soil communities

Beta diversity describes how local communities within an area or region differ in species composition/abundance. There have been attempts to use changes in beta diversity as a biotic indicator of disturbance, but lack of theory and methodological caveats have hampered progress. We here propose that the neutral theory of biodiversity plus the definition of beta diversity as the total variance of a community matrix provide a suitable, novel, starting point for ecological applications. Observed levels of beta diversity (BD) can be compared to neutral predictions with three possible outcomes: Observed BD equals neutral prediction or is larger (divergence) or smaller (convergence) than the neutral prediction. Disturbance might lead to either divergence or convergence, depending on type and strength. We here apply these ideas to datasets collected on oribatid mites (a key, very diverse soil taxon) under several regimes of disturbances. When disturbance is expected to increase the heterogeneity of soil spatial properties or the sampling strategy encompassed a range of diverging environmental conditions, we observed diverging assemblages. On the contrary, we observed patterns consistent with neutrality when disturbance could determine homogenization of soil properties in space or the sampling strategy encompassed fairly homogeneous areas. With our method, spatial and temporal changes in beta diversity can be directly and easily monitored to detect significant changes in community dynamics, although the method itself cannot inform on underlying mechanisms. However, human-driven disturbances and the spatial scales at which they operate are usually known. In this case, our approach allows the formulation of testable predictions in terms of expected changes in beta diversity, thereby offering a promising monitoring tool.

CHROMIUM(II)-MEDIATED CONVERSION OF ALPHA,BETA-UNSATURATED ALDEHYDES TO CYCLOPROPANOLS

Chromium(II) chloride converts alpha,beta-unsaturated aldehydes to the corresponding cyclopropanols.

A multivariate analysis of beta diversity across organisms and environments

We examined variability in hierarchical beta diversity across ecosystems, geographical gradients, and organism groups using multivariate spatial mixed modeling analysis of two independent data sets. The larger data set comprised reported ratios of regional species richness (RSR) to local species richness (LSR) and the second data set consisted of RSR: LSR ratios derived from nested species-area relationships. There was a negative, albeit relatively weak, relationship between beta diversity and latitude. We found only relatively subtle differences in beta diversity among the realms, yet beta diversity was lower in marine systems than in terrestrial or freshwater realms. Beta diversity varied significantly among organisms' major characteristics such as body mass, trophic position, and dispersal type in the larger data set. Organisms that disperse via seeds had highest beta diversity, and passively dispersed organisms showed the lowest beta diversity. Furthermore, autotrophs had lower beta diversity than organisms higher up the food web; omnivores and carnivores had consistently higher beta diversity. This is evidence that beta diversity is simultaneously controlled by extrinsic factors related to geography and environment, and by intrinsic factors related to organism characteristics.