Biofilm production by clinical strains of Acinetobacter baumannii isolated from patients hospitalized in two tertiary care hospitals

Microbial biofilms are considered as virulence factors. During the present study, 34 clinical strains of Acinetobacter baumannii, isolated from patients hospitalized in two tertiary care hospitals, were examined for biofilm formation. These strains showed high variability in biofilm formation. Furthermore, no relation could be found between the ability of biofilm production and molecular type, carbapenem resistance, site of isolation of the clinical strains of A. baumannii and disease severity. Interestingly, in two cases an increase in biofilm formation could be detected in A. baumannii isolates cultured from the same patient upon prolonged hospitalization.     

Development of a physics-based force field for the scoring and refinement of protein models

The minimal requirements of a physics-based potential that can refine protein structures are the existence of a correlation between the energy with native similarity and the scoring of the native structure as the lowest in energy. To develop such a force field, the relative weights of the Amber ff03 all-atom potential supplemented by an explicit hydrogen-bond potential were adjusted by global optimization of energetic and structural criteria for a large set of protein decoys generated for a set of 58 nonhomologous proteins. The average correlation coefficient of the energy with TM-score significantly improved from 0.25 for the original ff03 potential to 0.65 for the optimized force field. The fraction of proteins for which the native structure had lowest energy increased from 0.22 to 0.90. Moreover, use of an explicit hydrogen-bond potential improves scoring performance of the force field. Promising preliminary results were obtained in applying the optimized potentials to refine protein decoys using only an energy criterion to choose the best decoy among sampled structures. For a set of seven proteins, 63% of the decoys improve, 18% get worse, and 19% are not changed.     

Tetradecylthioacetic acid prevents the inflammatory response in two-kidney, one-clip hypertension

ANG II promotes inflammation through nuclear factor-kappaB (NF-kappaB)-mediated induction of cytokines and reactive oxygen species (ROS). The aim of the present study was to examine the effect of tetradecylthioacetic acid (TTA), a modified fatty acid, on NF-kappaB, proinflammatory markers, ROS, and nitric oxide (NO) production in two-kidney, one-clip (2K1C) hypertension. The 2K1C TTA-treated group had lower blood pressure (128 +/- 3 mmHg) compared with 2K1C nontreated (178 +/- 5 mmHg, P < 0.001). The p50 and p65 subunits of NF-kappaB were higher in the clipped kidney (0.44 +/- 0.01 and 0.22 +/- 0.01, respectively) compared with controls (0.25 +/- 0.03 and 0.12 +/- 0.02, respectively, P < 0.001). In the 2K1C TTA-treated group, these values were similar to control levels. The same pattern of response was seen in the nonclipped kidney. In 2K1C hypertension, cytokines plasma were higher than in control: TNF-alpha was 13.5 +/- 2 pg/ml (P < 0.03), IL-1beta was 58.8 +/- 10 pg/ml (P = 0.003), IL-6 was 210 +/- 33 pg/ml (P < 0.001), and monocyte chemoattractant protein-1 was 429 +/- 21 pg/ml (P = 0.04). In the 2K1C TTA-treated group, these values were similar to controls, and the same pattern was seen in the clipped kidney. Clipping increased 8-iso-PGF-2alpha (P < 0.01) and decreased NO production (P < 0.01 vs. control) in the urine. TTA treatment normalized these values. NO production was also lower in clipped and nonclipped kidney (P < 0.001). After TTA treatment, these values were similar to controls. The results indicate that TTA has a potent anti-inflammatory effect in 2K1C by inhibition of p50/p65 NF-kappaB subunit activation, reduction of cytokines production and ROS, and enhanced NO production.     

Evaluation of Nostoc Strain ATCC 53789 as a Potential Source of Natural Pesticides

The cyanobacterium Nostoc strain ATCC 53789, a known cryptophycin producer, was tested for its potential as a source of natural pesticides. The antibacterial, antifungal, insecticidal, nematocidal, and cytotoxic activities of methanolic extracts of the cyanobacterium were evaluated. Among the target organisms, nine fungi (Armillaria sp., Fusarium oxysporum f. sp. melonis, Penicillium expansum, Phytophthora cambivora, P. cinnamomi, Rhizoctonia solani, Rosellinia, sp., Sclerotinia sclerotiorum, and Verticillium albo-atrum) were growth inhibited and one insect (Helicoverpa armigera) was killed by the extract, as well as the two model organisms for nematocidal (Caenorhabditis elegans) and cytotoxic (Artemia salina) activity. No antibacterial activity was detected. The antifungal activity against S. sclerotiorum was further studied with both extracts and biomass of the cyanobacterium in a system involving tomato as a host plant. Finally, the herbicidal activity of Nostoc strain ATCC 53789 was evaluated against a grass mixture. To fully exploit the potential of this cyanobacterium in agriculture as a source of pesticides, suitable application methods to overcome its toxicity toward plants and nontarget organisms must be developed.     

Metals contents in two fishes of different feeding behaviour in the Lower Paraná River and Río de la Plata Estuary

Cd, Cr, Cu and Pb concentrations were measured in the water and these plus Zn were measured in the diet, muscle and liver of the detritivorous fish Prochilodus lineatus and the omnivorous fish Pterodoras granulosus at two sites (Lower Paraná River and Río de la Plata right margin) located upstream and downstream, respectively, from Buenos Aires, an important source of xenobiotics. Cu and Cr concentrations in water were higher in the Río de la Plata coastal waters, while Cd and Pb were below detection limits. The stomach contents of P. lineatus showed a higher metal content at the estuary, attaining concentrations within the range reported for contaminated sediments. However, metals in fish tissue were not higher at the estuary and, except for Cd in liver, were lower than in the organic fraction of the stomach content. Thus, only Cd was accumulated. The P. granulosus diet was composed mainly of river vegetation debris and clams, Corbicula fluminea, at the estuary. Cd, Cu and Pb in liver were higher at the estuary while only Cu was higher in the diet at this site. The different nature of the diet seems associated with a differential bioavailability of its metal content. P. granulosus accumulates Cu at both sites and Cd at the estuary. Both fishes showed higher metal content in liver than in muscle. Cr in liver was below detection limits. No relation was found between metal content and fish size. Overall, metal content in fish tissues were low, except for Cu in P. granulosus and Cd in P. lineatus, similar to those of uncontaminated sites, suggesting that homeostatic mechanisms prevent metal accumulation.     

Biotransformation of Natural and Synthetic Isoflavonoids by Two Recombinant Microbial Enzymes

Isolation and synthesis of isoflavonoids has become a frequent endeavor, due to their interesting biological activities. The introduction of hydroxyl groups into isoflavonoids by the use of enzymes represents an attractive alternative to conventional chemical synthesis. In this study, the capabilities of biphenyl-2,3-dioxygenase (BphA) and biphenyl-2,3-dihydrodiol 2,3-dehydrogenase (BphB) of Burkholderia sp. strain LB400 to biotransform 14 isoflavonoids synthesized in the laboratory were investigated by using recombinant Escherichia coli strains containing plasmid vectors expressing the bphA1A2A3A4 or bphA1A2A3A4B genes of strain LB400. The use of BphA and BphB allowed us to biotransform 7-hydroxy-8-methylisoflavone and 7-hydroxyisoflavone into 7,2′,3′-trihydroxy-8-methylisoflavone and 7,3′,4′-trihydroxyisoflavone, respectively. The compound 2′-fluoro-7-hydroxy-8-methylisoflavone was dihydroxylated by BphA at ortho-fluorinated and meta positions of ring B, with concomitant dehalogenation leading to 7,2′,3′,-trihydroxy-8-methylisoflavone. Daidzein (7,4′-dihydroxyisoflavone) was biotransformed by BphA, generating 7,2′,4′-trihydroxyisoflavone after dehydration. Biotransformation products were analyzed by gas chromatography-mass spectrometry and nuclear magnetic resonance techniques.     

Exploring the Factor Structure of Neurocognitive Measures in Older Individuals

Here we focus on factor analysis from a best practices point of view, by investigating the factor structure of neuropsychological tests and using the results obtained to illustrate on choosing a reasonable solution. The sample (n=1051 individuals) was randomly divided into two groups: one for exploratory factor analysis (EFA) and principal component analysis (PCA), to investigate the number of factors underlying the neurocognitive variables; the second to test the “best fit” model via confirmatory factor analysis (CFA). For the exploratory step, three extraction (maximum likelihood, principal axis factoring and principal components) and two rotation (orthogonal and oblique) methods were used. The analysis methodology allowed exploring how different cognitive/psychological tests correlated/discriminated between dimensions, indicating that to capture latent structures in similar sample sizes and measures, with approximately normal data distribution, reflective models with oblimin rotation might prove the most adequate.     

β-d-Glucosidase stabilization in a polarized ultrafiltration membrane reactor

Cellobiose hydrolysis by β-d-glucosidase (β-d-glucoside glucohydrolase EC 3.2.1.21) can become the rate-limiting step in the hydrolysis of cellulosic wastes because of inhibition phenomena involving other enzymes of the cellulase complex. Enhancement of the overall rate can therefore be obtained by increasing the amount of β-d-glucosidase present in the reactor. Unfortunately, the thermal stability of β-d-glucosidase is rather poor compared to $\text{endo}\text{-(1 → 4)-β-}\text{d}\text{-}\text{glucanase}$ and cellobiohydrolase. A novel stabilization method is proposed that exploits the polarization phenomena that take place in an unstirred ultrafiltration membrane enzymatic reactor. As much as a 20-fold increase in half-life compared to the native enzyme is obtained by injecting small amounts of hydroxyethyl cellulose into the system. No reduction in enzyme activity levels is observed.     

Novel Escherichia coli RF1 mutants with decreased translation termination activity and increased sensitivity to the cytotoxic effect of the bacterial toxins Kid and RelE

Novel mutations in prfA , the gene for the polypeptide release factor RF1 of Escherichia coli , were isolated using a positive genetic screen based on the parD ( kis , kid ) toxin–antitoxin system. This original approach allowed the direct selection of mutants with altered translational termination efficiency at UAG codons. The isolated prfA mutants displayed a ∼10-fold decrease in UAG termination efficiency with no significant changes in RF1 stability in vivo . All three mutations, G121S, G301S and R303H, were situated close to the nonsense codon recognition site in RF1:ribosome complexes. The prfA mutants displayed increased sensitivity to the RelE toxin encoded by the relBE system of E. coli , thus providing in vivo support for the functional interaction between RF1 and RelE. The prfA mutants also showed increased sensitivity to the Kid toxin. Since this toxin can cleave RNA in a ribosome-independent manner, this result was not anticipated and provided first evidence for the involvement of RF1 in the pathway of Kid toxicity. The sensitivity of the prfA mutants to RelE and Kid was restored to normal levels upon overproduction of the wild-type RF1 protein. We discuss these results and their utility for the design of novel antibacterial strategies in the light of the recently reported structure of ribosome-bound RF1.     

Geolocators reveal migratory connectivity between wintering and breeding areas of Golden‐winged Warblers

The conservation of migratory songbirds is often impeded by a lack of understanding of how populations in breeding and wintering areas are geographically linked (migratory connectivity). In recent years, light‐level geolocators have improved our understanding of migratory connectivity. Such information is valuable for evaluating how conservation efforts align between the breeding and non‐breeding areas of at‐risk species, and help to more effectively prioritize the allocation of conservation funding. Golden‐winged Warblers (Vermivora chrysoptera) are imperiled migratory songbirds, but the extent to which conservation efforts in their breeding and non‐breeding areas coincide with patterns of migratory connectivity are not well known. We used light‐level geolocators to evaluate the extent to which conservation actions targeting Golden‐winged Warblers in Nicaragua and in their breeding range in North America align with patterns of migratory connectivity. We recovered six of 22 geolocators that had been deployed on male Golden‐winged Warblers at the El Jaguar Reserve during the winter of 2015–2016. All six males migrated to breeding areas in the western Great Lakes region that includes eastern Minnesota, northern Wisconsin, southwestern Ontario, and Michigan's Upper Peninsula. All six males also had similar migration routes, with spring stopovers in southern Mexico, Guatemala, and Belize, a trans‐Gulf flight, and a stopover in the region of Louisiana, Arkansas, eastern Oklahoma, and Texas. Our results, in combination with those of previous studies, demonstrate strong migratory connectivity between portions of the breeding and winter distributions of Golden‐winged Warblers currently targeted for conservation. However, additional studies are needed to improve our understanding of the stopover ecology of Golden‐winged Warblers, especially in areas where they remain for extended periods of time. Finally, patterns of migratory connectivity revealed in our study should be used in combination with existing demographic parameters for Golden‐winged Warblers in the western Great Lakes and Nicaragua to help inform full life cycle population models for this imperiled songbird.