The Microbiota Mediates Pathogen Clearance from the Gut Lumen after Non-Typhoidal Salmonella Diarrhea

Many enteropathogenic bacteria target the mammalian gut. The mechanisms protecting the host from infection are poorly understood. We have studied the protective functions of secretory antibodies (sIgA) and the microbiota, using a mouse model for S. typhimurium diarrhea. This pathogen is a common cause of diarrhea in humans world-wide. S. typhimurium (S. tm ^att, sseD) causes a self-limiting gut infection in streptomycin-treated mice. After 40 days, all animals had overcome the disease, developed a sIgA response, and most had cleared the pathogen from the gut lumen. sIgA limited pathogen access to the mucosal surface and protected from gut inflammation in challenge infections. This protection was O-antigen specific, as demonstrated with pathogens lacking the S. typhimurium O-antigen (wbaP, S. enteritidis) and sIgA-deficient mice (TCRβ^−/−δ^−/−, J_H ^−/−, IgA^−/−, pIgR^−/−). Surprisingly, sIgA-deficiency did not affect the kinetics of pathogen clearance from the gut lumen. Instead, this was mediated by the microbiota. This was confirmed using ‘L-mice’ which harbor a low complexity gut flora, lack colonization resistance and develop a normal sIgA response, but fail to clear S. tm ^att from the gut lumen. In these mice, pathogen clearance was achieved by transferring a normal complex microbiota. Thus, besides colonization resistance ( = pathogen blockage by an intact microbiota), the microbiota mediates a second, novel protective function, i.e. pathogen clearance. Here, the normal microbiota re-grows from a state of depletion and disturbed composition and gradually clears even very high pathogen loads from the gut lumen, a site inaccessible to most “classical” immune effector mechanisms. In conclusion, sIgA and microbiota serve complementary protective functions. The microbiota confers colonization resistance and mediates pathogen clearance in primary infections, while sIgA protects from disease if the host re-encounters the same pathogen. This has implications for curing S. typhimurium diarrhea and for preventing transmission.     

Harnessing microbially generated power on the seafloor

In many marine environments, a voltage gradient exists across the water sediment interface resulting from sedimentary microbial activity. Here we show that a fuel cell consisting of an anode embedded in marine sediment and a cathode in overlying seawater can use this voltage gradient to generate electrical power in situ. Fuel cells of this design generated sustained power in a boat basin carved into a salt marsh near Tuckerton, New Jersey, and in the Yaquina Bay Estuary near Newport, Oregon. Retrieval and analysis of the Tuckerton fuel cell indicates that power generation results from at least two anode reactions: oxidation of sediment sulfide (a by-product of microbial oxidation of sedimentary organic carbon) and oxidation of sedimentary organic carbon catalyzed by microorganisms colonizing the anode. These results demonstrate in real marine environments a new form of power generation that uses an immense, renewable energy reservoir (sedimentary organic carbon) and has near-immediate application.     

Substrate degradation kinetics, microbial diversity, and current efficiency of microbial fuel cells supplied with marine plankton

The decomposition of marine plankton in two-chamber, seawater-filled microbial fuel cells (MFCs) has been investigated and related to resulting chemical changes, electrode potentials, current efficiencies, and microbial diversity. Six experiments were run at various discharge potentials, and a seventh served as an open-circuit control. The plankton consisted of a mixture of freshly captured phytoplankton and zooplankton (0.21 to 1 mm) added at an initial batch concentration of 27.5 mmol liter(-1) particulate organic carbon (OC). After 56.7 days, between 19.6 and 22.2% of the initial OC remained, sulfate reduction coupled to OC oxidation accounted for the majority of the OC that was degraded, and current efficiencies (of the active MFCs) were between 11.3 and 15.5%. In the open-circuit control cell, anaerobic plankton decomposition (as quantified by the decrease in total OC) could be modeled by three terms: two first-order reaction rate expressions (0.79 day(-1) and 0.037 day(-1), at 15 degrees C) and one constant, no-reaction term (representing 10.6% of the initial OC). However, in each active MFC, decomposition rates increased during the third week, lagging just behind periods of peak electricity generation. We interpret these decomposition rate changes to have been due primarily to the metabolic activity of sulfur-reducing microorganisms at the anode, a finding consistent with the electrochemical oxidization of sulfide to elemental sulfur and the elimination of inhibitory effects of dissolved sulfide. Representative phylotypes, found to be associated with anodes, were allied with Delta-, Epsilon-, and Gammaproteobacteria as well as the Flavobacterium-Cytophaga-Bacteroides and Fusobacteria. Based upon these results, we posit that higher current efficiencies can be achieved by optimizing plankton-fed MFCs for direct electron transfer from organic matter to electrodes, including microbial precolonization of high-surface-area electrodes and pulsed flowthrough additions of biomass.     

Involvement of a 65 kDa phosphoprotein in the regulation of membrane fusion during exocytosis in Paramecium cells

Antisera were raised against a phosphoprotein of 65 kDa (PP65) from Paramecium cells (shown before to be selectively dephosphorylated during synchronous exocytosis) and specified by immunoblotting. By immunofluorescence PP65 has been localized within the cortex, beneath the cell membrane. This corresponds to data obtained by cell fractionation, applying SDS-PAGE autoradiography to cortices prepared from 32P-prelabeled cells. Antisera against PP65 inhibit exocytosis in vivo (microinjection). Applying anti-PP65 antisera in vitro to cortices we could demonstrate inhibition not only of exocytosis, but also of PP65 dephosphorylation. We conclude that PP65 is involved in the regulation of membrane fusion during exocytosis.     

A caveat for the use of log P values for the assessment of the biocompatibility of organic solvents

The degree of enzyme deactivation for lipases from Candida rugosa and Pseudomonas sp., hydroxynitrile lyase and mandelate racemase upon exposure to organic solvents can be correlated to their respective partition coefficients (log P values). However, three unexpected results were obtained: (1) the deactivation exerted by protic solvents, e.g., methanol, is severely underestimated; (2) little deactivation by an organic solvent cannot neccessarily be correlated to catalytic activity in this medium, and (3) in contrast to other enzymes, hydroxynitrile lyase is exceptionally stable towards deactivation by DMF.     

Enzymatic features of the glucose metabolism in tumor cells

Many tumor types exhibit an impaired Pasteur effect, i.e. despite the presence of oxygen, glucose is consumed at an extraordinarily high rate compared with the tissue from which they originate - the so-called 'Warburg effect'. Glucose has to serve as the source for a diverse array of cellular functions, including energy production, synthesis of nucleotides and lipids, membrane synthesis and generation of redox equivalents for antioxidative defense. Tumor cells acquire specific enzyme-regulatory mechanisms to direct the main flux of glucose carbons to those pathways most urgently required under challenging external conditions such as varying substrate availability, presence of anti-cancer drugs or different phases of the cell cycle. In this review we summarize the currently available information on tumor-specific expression, activity and kinetic properties of enzymes involved in the main pathways of glucose metabolism with due regard to the explanation of the regulatory basis and physiological significance of the Warburg effect. We conclude that, besides the expression level of the metabolic enzymes involved in the glucose metabolism of tumor cells, the unique tumor-specific pattern of isozymes and accompanying changes in the metabolic regulation below the translation level enable tumor cells to drain selfishly the blood glucose pool that non-transformed cells use as sparingly as possible.     

Salmonella Typhimurium Strain ATCC14028 Requires H2-Hydrogenases for Growth in the Gut,but Not at Systemic Sites

Salmonella enterica is a common cause of diarrhea. For eliciting disease, the pathogen has to colonize the gut lumen, a site colonized by the microbiota. This process/initial stage is incompletely understood. Recent work established that one particular strain, Salmonella enterica subspecies 1 serovar Typhimurium strain SL1344, employs the hyb H₂-hydrogenase for consuming microbiota-derived H₂ to support gut luminal pathogen growth: Protons from the H₂-splitting reaction contribute to the proton gradient across the outer bacterial membrane which can be harvested for ATP production or for import of carbon sources. However, it remained unclear, if other Salmonella strains would use the same strategy. In particular, earlier work had left unanswered if strain ATCC14028 might use H₂ for growth at systemic sites. To clarify the role of the hydrogenases, it seems important to establish if H₂ is used at systemic sites or in the gut and if Salmonella strains may differ with respect to the host sites where they require H₂ in vivo. In order to resolve this, we constructed a strain lacking all three H₂-hydrogenases of ATCC14028 (14028^hyd3) and performed competitive infection experiments. Upon intragastric inoculation, 14028^hyd3 was present at 100-fold lower numbers than 14028^WT in the stool and at systemic sites. In contrast, i.v. inoculation led to equivalent systemic loads of 14028^hyd3 and the wild type strain. However, the pathogen population spreading to the gut lumen featured again up to 100-fold attenuation of 14028^hyd3. Therefore, ATCC14028 requires H₂-hydrogenases for growth in the gut lumen and not at systemic sites. This extends previous work on ATCC14028 and supports the notion that H₂-utilization might be a general feature of S. Typhimurium gut colonization.     

TimeTree 5: An Expanded Resource for Species Divergence Times

We present the fifth edition of the TimeTree of Life resource (TToL5), a product of the timetree of life project that aims to synthesize published molecular timetrees and make evolutionary knowledge easily accessible to all. Using the TToL5 web portal, users can retrieve published studies and divergence times between species, the timeline of a species’ evolution beginning with the origin of life, and the timetree for a given evolutionary group at the desired taxonomic rank. TToL5 contains divergence time information on 137,306 species, 41% more than the previous edition. The TToL5 web interface is now Americans with Disabilities Act-compliant and mobile-friendly, a result of comprehensive source code refactoring. TToL5 also offers programmatic access to species divergence times and timelines through an application programming interface, which is accessible at timetree.temple.edu/api. TToL5 is publicly available at timetree.org.     

Reproductive potential of gamma-irradiated males of the meadow grasshopper Chorthippus parallelus (Zetterstedt) (Orth., Acrididae)

Males of the meadow grasshopper Chorthippus parallelus were treated with five doses ranging from 0 (control) to 140 Gy of gamma irradiation. There was a negative correlation between irradiation dose and post-treatment longevity. Individuals irradiated with the lowest dose lived, on average, longer than the controls. This was presumably not attributable to an energy allocation from tissue since at the time of death there were no dry weight differences. There was a negative correlation between irradiation dose and number of faecal pellets excreted in a period 6–9 days after treatment but not before. There were no negative correlations between irradiation dose and the time required to copulate, copulation duration and ejaculate size. The proportion of tail-less sperm did not differ between the treatments.     

Ferrous Sulfate Supplementation Causes Significant Gastrointestinal Side-Effects in Adults: A Systematic Review and Meta-Analysis

BackgroundThe tolerability of oral iron supplementation for the treatment of iron deficiency anemia is disputed.ObjectiveOur aim was to quantify the odds of GI side-effects in adults related to current gold standard oral iron therapy, namely ferrous sulfate.MethodsSystematic review and meta-analysis of randomized controlled trials (RCTs) evaluating GI side-effects that included ferrous sulfate and a comparator that was either placebo or intravenous (IV) iron. Random effects meta-analysis modelling was undertaken and study heterogeneity was summarised using I² statistics.ResultsForty three trials comprising 6831 adult participants were included. Twenty trials (n = 3168) had a placebo arm and twenty three trials (n = 3663) had an active comparator arm of IV iron. Ferrous sulfate supplementation significantly increased risk of GI side-effects versus placebo with an odds ratio (OR) of 2.32 [95% CI 1.74–3.08, p<0.0001, I² = 53.6%] and versus IV iron with an OR of 3.05 [95% CI 2.07-4.48, p<0.0001, I² = 41.6%]. Subgroup analysis in IBD patients showed a similar effect versus IV iron (OR = 3.14, 95% CI 1.34-7.36, p = 0.008, I² = 0%). Likewise, subgroup analysis of pooled data from 7 RCTs in pregnant women (n = 1028) showed a statistically significant increased risk of GI side-effects for ferrous sulfate although there was marked heterogeneity in the data (OR = 3.33, 95% CI 1.19-9.28, p = 0.02, I² = 66.1%). Meta-regression did not provide significant evidence of an association between the study OR and the iron dose.ConclusionsOur meta-analysis confirms that ferrous sulfate is associated with a significant increase in gastrointestinal-specific side-effects but does not find a relationship with dose.