Dinitrogen-Fixing Cyanobacteria in Microbial Mats of Two Shallow Coral Reef Ecosystems

Dinitrogen-fixing organisms in cyanobacterial mats were studied in two shallow coral reef ecosystems: La Reunion Island, southwestern Indian Ocean, Sesoko (Okinawa) Island, and northwestern Pacific Ocean. Rapidly expanding benthic miniblooms, frequently dominated by a single cyanobacterial taxon, were identified by microscopy and molecular tools. In addition, nitrogenase activity by these blooms was measured in situ. Dinitrogen fixation and its contribution to mat primary production were calculated using ¹⁵N₂ and ¹³C methods. Dinitrogen-fixing cyanobacteria from mats in La Reunion and Sesoko showed few differences in taxonomic composition. Anabaena sp. among heterocystous and Hydrocoleum majus and Symploca hydnoides among nonheterocystous cyanobacteria occurred in microbial mats of both sites. Oscillatoria bonnemaisonii and Leptolyngbya spp. occurred only in La Reunion, whereas Hydrocoleum coccineum dominated in Sesoko. Other mats dominated by Hydrocoleum lyngbyaceum, Phormidium laysanense, and Trichocoleus tenerrimus occurred at lower frequencies. The 24-h nitrogenase activity, as measured by acetylene reduction, varied between 11 and 324 nmoles C₂H₂ reduced μg⁻¹ Chl a. The highest values were achieved by heterocystous Anabaena sp. performed mostly during the day. Highest values for nonheterocystous cyanobacteria were achieved by H. coccineum mostly during the night. Daily nitrogen fixation varied from nine (Leptolyngbya) to 238 nmoles N₂ μg⁻¹ Chl day⁻¹ (H. coccineum). Primary production rates ranged from 1,321 (S. hydnoides) to 9,933 nmoles C μg⁻¹ Chl day⁻¹ (H. coccineum). Dinitrogen fixation satisfied between 5% and 21% of the nitrogen required for primary production.     

In vivo biofilm composition of Aspergillus fumigatus

The in vivo composition of the mycelial extracellular matrix (ECM) of Aspergillus fumigatus during host invasion is reported here for the first time. A new galactosaminogalactan and the galactomannan were the major polysaccharides of the in vivo ECM. The composition of the ECM in vivo varied with the aspergillosis pathologies.     

Efficacy and safety of rabeprazole, amoxicillin, and gatifloxacin after treatment failure of initial Helicobacter pylori eradication

OBJECTIVES: To evaluate the efficacy of a 7-day regimen of gatifloxacin (400 mg daily), amoxicillin (1 g twice a day), and rabeprazole (20 mg twice a day) in the secondary eradication of Helicobacter pylori infection. METHODS: Eligible patients with persistent infection following one or more conventional clarithromycin-containing triple therapies were enrolled in this open-label trial. Eradication of infection was documented by (14)C-urea breath test a minimum of 4 weeks after therapy and 2 weeks off any acid suppressive therapy. Culture of H. pylori and in vitro susceptibility testing to amoxicillin, clarithromycin, and gatifloxacin was done in cases of failed eradication. RESULTS: A total of 45 patients (22 females:23 males; mean age 44.5 +/- 13 years) were enrolled. Eradication occurred in 38 patients [both per-protocol (PP) and intention-to-treat analysis: 84.4%; 95% CI: 74-95%]. No significant adverse effects were reported. In vitro susceptibility testing showed no secondary resistance to gatifloxacin or amoxicillin in any of the seven nonresponders. Smoking, age, and sex were not predictors of potential eradication failure. CONCLUSIONS: A 7-day regimen of gatifloxacin, rabeprazole, and amoxicillin is effective after failed eradication therapy for H. pylori and does not appear to result in secondary resistance. This combination is simple, well tolerated, and may lead to higher compliance and lower costs.     

Molecular characterization of carbapenem-resistant Pseudomonas aeruginosa isolated from four medical centres in Iran

Molecular Biology Reports - Understanding the mechanisms of antibiotic resistance is important for designing new therapeutic options and controlling resistant strains. The goal of this study was to...     

Role of termites in the restoration of soils and plant richness on bowé in West Africa

Bowé (hardened ferricrete soils formed by erosion, drought or deforestation) are often associated with termite mounds, but little is known about these mounds and their role in the restoration of soils and plant biodiversity on bowé. This study examined termite mounds on bowé and their effects on soil depth and plant richness. Sixty-four sampling plots were laid out randomly on bowé sites with mounds and on adjacent bowé sites without mounds. The height and circumference of each mound were measured. Species inventories were made and soil depth measured in each plot. Linear mixed effects and generalised mixed effects models with Poisson error distribution were used to assess the variation in soil depth and plant species richness in mound and nonmound microsites. Two types of mounds (small vs. large) associated with different termite species were observed on bowé, with the small mounds being most common. Plots with either large or small mounds had deeper soils and higher plant richness than the adjacent plots without mounds. Conservation of termite mounds is important for restoring soils and plant richness on bowé, and termite mounds should be taken into consideration in biodiversity and soil management strategies for bowé.