Polysaccharide production and biofilm formation by Pseudomonas fluorescens: effects of pH and surface material

Although the synthesis of extracellular polysaccharides was first recognized in certain bacterial cultures a long time ago, its role in bacterial adhesion is still subject to some debate. Several fermentation batch cultures were performed under different conditions of pH (pH 7, maintained with NaOH and HCl; pH 7 in phosphate buffer, and without pH control) in order to study the relation between the production of extracellular polysaccharides and biofilm formation on polymeric slides suspended in the culture medium. The polymers used were polystyrene, polypropylene, polyethylene and poly(vinyl chloride). The maximum amount of exopolysaccharides in the culture medium occurs at pH 7, although slightly thicker biofilms seem to be formed when there is no pH control. The biofilms were analysed by scanning electron microscopy and by wavelength dispersion spectroscopy. Biofilm morphology seems to be much more dependent on the type of substratium than on the pH of the medium; for different pH values, a polymeric network can be more clearly observed on biofilms formed on all surfaces except poly(vinyl chloride)

Social interaction by BV anaerobes in initial adhesion and biofilm assays

Bacterial vaginosis (BV) is the most common vaginal disorder of women of reproductive age. It is commonly accepted that the microbial switch from normal to BV state is characterized by a decrease in vaginal colonization by Lactobacillus species together with an increase in the number of Gardnerella vaginalis and others anaerobes. G. vaginalis can be found associated with normal vaginal epithelium but recent findings suggest that it is the biofilm produced by G. vaginalis that leads to establishment of BV, by allowing other anaerobes to grow. Further research into the properties of G. vaginalis and its interactions with other BV-associated anaerobes may be essential for better understanding the BV etiology. Therefore, our goal was to study competitive initial adhesion between Lactobacillus crispatus (an important vaginal species with probiotic activity) and several anaerobes. Also, this study aimed to evaluate differences in biofilm formation between a healthy G. vaginalis strain (5-1) and the other anaerobes as compared with a BV G. vaginalis strain (101). In addition to G. vaginalis strains (5-1 and 101), Prevotella bivia, Fusobacteria nucleatum, Mobiluncus mulieris and Atopobium vaginae were used in this social interaction research. First, initial adhesion assays at 100rpm for 30 min were conducted in glass 8-well slides using an equal mixture of L. crispatus 39G strain and a second anaerobe at same concentration (103 CFU/ml) in each well. Next, we used qPCR to study the biofilm social evolution (synergic, antagonist and commensal relationship) between a pre-established (24h) biofilm formed by one of the two G. vaginalis strains and a second anaerobe. Our results showed that G. vaginalis 5-1 and 101 strains had definitively the greatest initial adherence capability when in presence of the same number of L. crispatus 39G cells, followed by P. bivia, M. mulieris and A. vaginae. In addition, qPCR analysis of the two species biofilms revealed that both G. vaginalis strains established commensal relationships with all others anaerobes except with P. bivia, for which a synergic relation was found. In fact, this synergic relation between these two species had previously been noted. Importantly, G. vaginalis 101 (pathogenic strain) showed nearly a 2-fold increase in biofilm formation when compared with G. vaginalis 5-1 (healthy strain) in the presence of any other anaerobe studied

Magnetic phase transitions in Gd64Sc36 studied using non-contact ultrasonics

The speed and attenuation of ultrasound propagation can be used to determine material properties and identify phase transitions. Standard ultrasonic contact techniques are not always convenient due to the necessity of using couplant; however, recently reliable non-contact ultrasonic techniques involving electromagnetic generation and detection of ultrasound with electromagnetic acoustic transducers (EMATs) have been developed for use on electrically conducting and/or magnetic materials. We present a detailed study of magnetic phase transitions in a single crystal sample of Gd64Sc36 magnetic alloy using contact and non-contact ultrasonic techniques for two orientations of external magnetic field. Phase diagrams are constructed based on measurements of elastic constant C33, the attenuation and the efficiency of generation when using an EMAT. The EMATs are shown to provide additional information related to the magnetic phase transitions in the studied sample, and results identify a conical helix phase in Gd64Sc36 in the magnetic field orientation

Ocorrência de ouro nos depósitos pliocénicos da região de Cruz de Pau (Seixal)

Recently had been discovery, in the area of the construction of the Carla Sacramento Athletics Stadium at Cruz de Pau (Seixal), a set of stopes and wells with characteristics of ancient Roman mining activities. The old mining works are incised in pliocene sandy formations with conglomeratic facies, where four preliminary samples were collected in a coarser level with subrounded pebbles. The heavy minerais of those samples were studied in accordance with the Heavy Mineral Concentrate Laboratory of the IGM. The previously mentioned facies has interesting gold percentages and the presence of grey (nodular) and classic monazite, xenotime, cassiterite, spinels s.l., ilmenite and rutile. The morphology of the gold grains as well as the heavy minerals shows two phases of transport; an initial fluvial phase and a secondary aeolian phase influenced their concentracion. The high percentage of toroid grains showing evidence of wind ablation, suggests that this was the main factor for reconcentration of the gold. The amount of gold particles obtained in the concentrates is considerable and in one sample, a grade of 3.2 ppm was calculated. The samples also have been analysed for Au + 34 elements by INAA and ICP-MS, the results of which show similar grades as previously obtained

Antimicrobial activity of the essential oils of Dittrichia viscosa subsp viscosa on Helicobacter pylori

Dittrichia viscosa subsp. viscosa (Compositae) is found on edges, wood clearings and in waste places of the Iberian Peninsula. Aerial parts of D. viscosa were collected at flowering phase in September-October 2001 around Lisbon, Portugal and the essential oils isolated by hydro-distillation for 4 h using a Clevenger-type apparatus. The oils were analyzed by gas chromatography and gas chromatography-mass spectrometry. Preliminary examination of the essential oils allowed the identification of 32 components. Only four components reached percentages over 5%: fokienol (11.8%), T-muurorol (7.9%), (E)-nerolidol (5.5%) and delta-cadinene (5.0%). The essential oils were tested against Helicobacterpylori and Listeria monocytogenes. Essential oils did not have antimicrobial activity against L. monocytogenes. The essential oil at 0.88 to 22.22 mu g.ml(-1) did not inhibit the growth of H. pylori, affected the growth slightly at 44.40 mu g.ml(-1), and completely inhibited the growth at 88.80 to 133.20 mu g.ml(-1) Results show that use of D. viscosa essential oil in the treatment of gastric disorders caused by H. pylori can be effective

Antiplatelet agents and/or anticoagulants are not associated with worse outcome following nonvariceal upper gastrointestinal bleeding

BACKGROUND: Nonvariceal upper gastrointestinal bleeding emerges as a major complication of using antiplatelet agents and/or anticoagulants and represents a clinical challenge in patients undergoing these therapies. AIM: To characterize patients with nonvariceal upper gastrointestinal bleeding related to antithrombotics and their management, and to determine clinical predictors of adverse outcomes. METHODS: Retrospective cohort of adults who underwent upper gastrointestinal endoscopy after nonvariceal upper gastrointestinal bleeding from 2010 to 2012. The outcomes were compared between patients exposed and not exposed to antithrombotics. RESULTS: Five hundred and forty-eight patients with nonvariceal upper gastrointestinal bleeding (67% men; mean age 66.5 ± 16.4 years) were included, of which 43% received antithrombotics. Most patients had comorbidities. Peptic ulcer was the main diagnosis and endoscopic therapy was performed in 46% of cases. The 30-day mortality rate was 7.7% (n = 42), and 36% were bleeding-related. The recurrence rate was 9% and 14% of patients with initial endoscopic treatment needed endoscopic retreatment. There were no significant differences between the exposed and non-exposed groups in most outcomes. Co-morbidities, hemodynamic instability, high Rockall score, low hemoglobin (7.76 ± 2.72 g/dL) and higher international normalized ratio (1.63 ± 1.13) were associated significantly with mortality in a univariate analysis. CONCLUSIONS: Adverse outcomes were not associated with antithrombotic use. The management of nonvariceal upper gastrointestinal bleeding constitutes a challenge to clinical performance optimization and clinical cooperation.info:eu-repo/semantics/publishedVersio

Square vortex solitons with a large angular momentum

We show the existence of square shaped optical vortices with a large value of the angular momentum hosted in finite size laser beams which propagate in nonlinear media with a cubic-quintic nonlinearity. The light profiles take the form of rings with sharp boundaries and variable sizes depending on the power carried. Our stability analysis shows that these light distributions remain stable when propagate, probably for unlimited values of the angular momentum, provided the hosting beam is wide enough. This happens if the peak amplitude approaches a critical value which only depends on the nonlinear refractive index of the material. A variational approach allows us to calculate the main parameters involved. Our results add extra support to the concept of surface tension of light beams that can be considered as a trace of the existence of a liquid of light.Comment: 6 pages, 6 figures, submitted to Phys. Rev.

Stabilized vortex solitons in layered Kerr media

In this letter we demonstrate the possibility of stabilizing beams with angular momentum propagating in Kerr media. Large propagation distances without filamentation can be achieved in layered media with alternating focusing and defocusing nonlinearities. Stronger stabilization can be obtained with the addition of an incoherent beam.Comment: 4 pages, 3 figures. We have removed the sentence "Thus, they erroneously point out to the existence of fully stabilized vortex solitons" in page 2, column 2, line 7-8, because it might be confusin