Effect of ions on the organization of phosphatidylcholine/phosphatidic acid bilayers

Lipid bilayers are two-dimensional fluids. Here, the effect of monovalent ion concentration on the mixing, and consequently the organization, of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1,2-dioleoyl-sn-glycero-3-phosphate (DOPA) bilayers has been examined. Epifluorescence microscopy was used to visualize the organization. Fluorescence recovery after photobleaching and attenuated total reflection-Fourier transform infrared spectroscopy were used to assess the fluidity of the lipids. At high ionic strength the DOPC and DOPA lipids appear uniformly mixed. Upon lowering the ionic strength, rapid separation is observed. The DOPA-rich regions appear fractal-like and exhibit hysteresis in their properties. The lipids freely exchange between the two regions. These experiments clearly demonstrate the significant effect that electrostatics can have on membrane organization.     

Some thaumatin-like proteins hydrolyse polymeric β-1,3-glucans

Thaumatin and 12 purified thaumatin-like (TL) proteins were surveyed for their capacity to hydrolyse beta-1,3-glucans by using an in-gel glucanase assay. Six TL proteins identified by N-terminal amino acid microsequencing were found to be active on carboxymethyl(CM)-pachyman: a barley leaf stress-related permatin, two tomato fruit osmotins, a cherry fruit and two tobacco stigma proteins. TL enzymes ranged in specific activity from 0.07 to 89 nkat mg-1 with CM-pachyman as substrate. Hydrolytic activities were not restricted to TL proteins strongly binding to water-insoluble beta-1,3-glucans since the two osmotins were active without tight binding to pachyman. Some TL proteins hydrolysed crude fungal walls and one barley TL enzyme even lysed fungal spores. No activity was observed on laminarin in the in-gel hydrolase assay. Thin-layer chromatography revealed that the six enzymes acted as endo-beta-1, 3-glucanases leading to the formation of various oligoglucosides. Thus far, the TL enzymes (EC 3.2.1.x) appeared different from the well-known beta-1,3-glucanases (EC 3.2.1.39). No activity was found with thaumatin, zeamatin, tobacco leaf PR-R protein and four stress-related TL proteins from barley and pea. This is the first demonstration that diverse TL proteins are enzymatically active. The functions of some TL proteins must be reassessed because they display endo-beta-1,3-glucanase activity on polymeric beta-1, 3-glucans.     

Response to De Silva et al. (2007): Endemic freshwater finfish of Asia: distribution and conservation status

De Silva et al . (2007) present an overview of the distribution and conservation status of the endemic freshwater fish of Asia. Within that review they use data from the IUCN Red List of Threatened Species™ (2006) to conduct an analysis of the conservation status of those endemic fish species. Their analysis is incorrect and provides a very misleading impression of the level of threat to Asian freshwater fish and to freshwater fish at the global scale. The errors stem from a misinterpretation of the data presented on the IUCN Red List. The sources of errors are discussed below and the opportunity is taken to clarify what the information on the IUCN Red List represents.     

Fingerprinting the genetic diversity of the biotin carboxylase gene (accC) in aquatic ecosystems as a potential marker for studies of carbon dioxide assimilation in the dark

We designed and tested a set of specific primers for specific PCR amplification of the biotin carboxylase subunit gene (accC) of the Acetyl CoA carboxylase (ACCase) enzyme. The primer set yielded a PCR product of c. 460 bp that was suitable for denaturing gradient gel electrophoresis (DGGE) fingerprinting followed by direct sequencing of excised DGGE bands and sequence analysis. Optimization of PCR conditions for selective amplification was carried out with pure cultures of different bacteria and archaea, and laboratory enrichments. Next, fingerprinting comparisons were done in several aerobic and anaerobic freshwater planktonic samples. The DGGE fingerprints showed between 2 and 19 bands in the different samples, and the primer set provided specific amplification in both pure cultures and natural samples. Most of the samples had sequences grouped with bacterial accC, hypothetically related to the anaplerotic fixation of inorganic carbon. Some other samples, however, yielded accC gene sequences that clustered with Crenarchaeota and were related to the 3-hydroxypropionate/4-hydroxybutyrate cycle of autotrophic crenarchaeota. Such samples came from oligotrophic high mountain lakes and the hypolimnia of a sulfide-rich lake, where crenarchaeotal populations had been previously reported by 16S rRNA surveys. This study provided a fast tool to look for presence of accC genes in natural environments as potential marker for studies of carbon dioxide assimilation in the dark. After further refinement for better specificity against archaea, the new and novel primers could be very helpful to establish a target for crenarchaeota with implications for our understanding of archaeal carbon biogeochemistry.     

Ability of <Emphasis Type="Italic">Lactobacillus fermentum</Emphasis> to overcome host α-galactosidase deficiency,as evidenced by reduction of hydrogen excretion in rats consuming soya α-galacto-oligosaccharides

Background  

Soya and its derivatives represent nutritionally high quality food products whose major drawback is their high content of α-galacto-oligosaccharides. These are not digested in the small intestine due to the natural absence of tissular α-galactosidase in mammals. The passage of these carbohydrates to the large intestine makes them available for fermentation by gas-producing bacteria leading to intestinal flatulence. The aim of the work reported here was to assess the ability of α-galactosidase-producing lactobacilli to improve the digestibility of α-galacto-oligosaccharides in situ.     

Dissecting the genetic components of adaptation of Escherichia coli to the mouse gut

While pleiotropic adaptive mutations are thought to be central for evolution, little is known on the downstream molecular effects allowing adaptation to complex ecologically relevant environments. Here we show that Escherichia coli MG1655 adapts rapidly to the intestine of germ-free mice by single point mutations in EnvZ/OmpR two-component signal transduction system, which controls more than 100 genes. The selective advantage conferred by the mutations that modulate EnvZ/OmpR activities was the result of their independent and additive effects on flagellin expression and permeability. These results obtained in vivo thus suggest that global regulators may have evolved to coordinate activities that need to be fine-tuned simultaneously during adaptation to complex environments and that mutations in such regulators permit adjustment of the boundaries of physiological adaptation when switching between two very distinct environments.     

Pneumococcal vaccination and risk of myocardial infarction

Background

Based on promising results from laboratory studies, we hypothesized that pneumococcal vaccination would protect patients from myocardial infarction.

Methods

We conducted a hospital-based case–control study that included patients considered to be at risk of myocardial infarction. We used health databases to obtain hospital diagnoses and vaccination status. We compared patients who had been admitted for treatment of myocardial infarction with patients admitted to a surgical department in the same hospital for a reason other than myocardial infarction between 1997 and 2003.

Results

We found a total of 43 209 patients who were at risk; of these, we matched 999 cases and 3996 controls according to age, sex and year of hospital admission. Cases were less likely than controls to have been vaccinated (adjusted odds ratio [OR] 0.53, 95% confidence interval [CI] 0.40–0.70). This putative protective role of the vaccine was not observed for patients who had received the vaccine up to 1 year before myocardial infarction (adjusted OR 0.85, 95% CI 0.54–1.33). In contrast, if vaccination had occurred 2 years or more before the hospital admission, the association was stronger (adjusted OR 0.33, 95% CI 0.20–0.46).

Interpretation

Pneumococcal vaccination was associated with a decrease of more than 50% in the rate myocardial infarction 2 years after exposure. If confirmed, this association should generate interest in exploring the putative mechanisms and may offer another reason to promote pneumococcal vaccination.Despite important advances in primary prevention, atherosclerosis remains the leading cause of death in developed societies.¹ In addition to risk factors such as hypertension, diabetes mellitus, tobacco use and dyslipidemia, less traditional risk factors have also been sought. Many markers, including C-reactive protein and interleukins, highlight inflammation as a key mediator in both the progression and activation of atherosclerotic lesions.^2–4 Some medications that are used to prevent cardiovascular diseases, such as statins, also appear to reduce inflammation.⁵Animal experiments have shown that pneumococcal vaccination reduces the extent of atherosclerotic lesions.⁶ We hypothesized that antibodies directed against Streptococcus pneumoniae also recognize oxidized low-density lipoprotein (LDL) and impede the formation of foam cells. Interestingly, a retrospective cohort study involving World War II veterans who had undergone splenectomy documented excess mortality rates from both pneumonia and ischemic heart disease.⁷ More recent data have suggested that acute pneumococcal infections, but not vaccinations, increase the risk of vascular events;⁸ however, the duration of vaccination exposure considered in that study was limited.Our primary objective was to evaluate the association between pneumococcal vaccination and the risk of myocardial infarction. We also explored whether any effect of vaccination on the risk of infarction waned over time.     

The carriage population of Staphylococcus aureus from Mali is composed of a combination of pandemic clones and the divergent Panton-Valentine leukocidin-positive genotype ST152

Staphylococcus aureus is an important human pathogen, but it appears more commonly in asymptomatic colonization of the nasopharynx than in cases of invasive disease. Evidence concerning the global population structure of S. aureus is limited by the overrepresentation in the multilocus sequence testing database of disease isolates recovered from Western Europe, the Americas, Australia, and Japan. We address this by presenting data from the S. aureus carriage population in Mali, the first detailed characterization of asymptomatic carriage from an African population. These data confirm the pandemic spread of many of the common S. aureus clones in the carriage population. We also note the high frequency (approximately 24%) of a single divergent genotype, sequence type 152 (ST152), which has not previously been recovered from nasal carriage isolates but corresponds to a sporadic Panton-Valentine leukocidin (PVL)-positive, community-acquired methicillin-resistant S. aureus clone noted mostly in Central Europe. We show that 100% of the ST152 isolates recovered from nasal carriage samples in Mali are PVL positive and discuss implications relating to the emergence and spread of this virulent genotype.     

Kinetics of drought-induced pathogenesis-related proteins and its physiological significance in white clover leaves

To investigate the responses of pathogenesis-related (PR) proteins to the intensity of drought stress and their physiological significance in white clover ( Trifolium repens L.), the change of enzyme activity and its relationship with some physiological parameters were assessed for 28 days under well-watered (control) and water-deficit conditions. Water-deficit treatment gradually decreased leaf water potential (Ψ_w) to −2.33 MPa at day 28. Dry matter significantly decreased from 21 days of water-deficit treatment, while proline and ammonia concentration increased within 7 days. The increase in PR-protein activity was closely related with the decrease in Ψ_w. The β-1,3-glucanase (EC 3.2.1.39) activity in water-deficit leaves rapidly increased for the first 14 days (Ψ_w ≥ −1.67) and then slightly decreased, while the chitinase (EC 3.2.1.14) and cellulase (EC 3.2.1.4) activity continued to increase throughout the experimental period. The enhanced activation of β-1,3-glucanase, chitinase and cellulase for the period of days 0–14 was significantly ( P  ≤ 0.01) related to the increase of proline and ammonia concentrations. The results indicate that the enhanced activity of β-1,3-glucanase, cellulase and chitinase for the early period might be an act of transient tolerance to drought stress, but the activation of these enzymes during terminal stress might be a drought-stress-induced injurious symptom.