Salmonella typhimurium and Escherichia coli dissimilarity: closely related bacteria with distinct metabolic profiles

Live attenuated strains of Salmonella typhimurium have been extensively investigated as vaccines for a number of infectious diseases. However, there is still little information available concerning aspects of their metabolism. S. typhimurium and Escherichia coli show a high degree of similarity in terms of their genome contents and metabolic networks. However, this work presents experimental evidence showing that significant differences exist in their abilities to direct carbon fluxes to biomass and energy production. It is important to study the metabolism of Salmonella in order to elucidate the formation of acetate and other metabolites involved in optimizing the production of biomass, essential for the development of recombinant vaccines. The metabolism of Salmonella under aerobic conditions was assessed using continuous cultures performed at dilution rates ranging from 0.1 to 0.67 h1, with glucose as main substrate. Acetate assimilation and glucose metabolism under anaerobic conditions were also investigated using batch cultures. Chemostat cultivations showed deviation of carbon towards acetate formation, starting at dilution rates above 0.1 h1. This differed from previous findings for E. coli, where acetate accumulation was only detected at dilution rates exceeding 0.4 h1, and was due to the lower rate of acetate assimilation by S. typhimurium under aerobic conditions. Under anaerobic conditions, both microorganisms mainly produced ethanol, acetate, and formate. A genome-scale metabolic model, reconstructed for Salmonella based on an E. coli model, provided a poor description of the mixed fermentation pattern observed during Salmonella cultures, reinforcing the different patterns of carbon utilization exhibited by these closely related bacteria. This article is protected by copyright. All rights reserved.Special thanks to Amadeus Azevedo for the HPLC analyses and technical assistance. The authors acknowledge the national funding received from CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, Brazil), the international cooperation project CAPES-FCT (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior/Brazil-Fundacao para a Ciencia e a Tecnologia/Portugal-Process 315/11), CAPES (Atracao de Jovens Talentos-Process 064922/2014-01) and to Fundacao para a Ciencia e Tecnologia the strategic funding of UID/BIO/04469/2013 unit

Improved photocatalytic activity of d-FeOOH by using H2O2 as an electron acceptor.

In this work, d-FeOOH nanoparticles were synthesized by a simple co-precipitation method and used as a photocatalyst in the presence of H2O2 for the oxidation of Rhodamine B (RhB) dye under artificial light. The d-FeOOH was characterized by powder X-ray diffraction, 57Fe M?ssbauer spectroscopy, N2 adsorption/desorption and UV?vis diffuse reflectance measurements. The d-FeOOH nanoparticles have high specific surface area (101 m2 g 1) and optical bandgap energy of 2.02 eV. Under artificial light, only 59% of RhB (100 mL; 20 mg L 1) was photocatalytically degraded by d-FeOOH in 60 min reaction. However, after adding H2O2, the photocatalytic activity of d-FeOOH was significantly improved, reaching 87% of dye removal. Tests using scavengers of reactive species and EPR analysis revealed that h+ and OH are the main species in this system. Based on the experimental results, the mechanism of RhB photodegradation in the presence of d-FeOOH and H2O2 was proposed. By this mechanism, the OH can be formed by direct water oxidation or by H2O2 reduction, as the electron transfer from the conduction band of d-FeOOH to H2O2 is thermodynamically favorable. Moreover, the H2O2 retards the electron-hole recombination in d-FeOOH, thus increasing its photocatalytic activity. Given its high efficiency for degrading RhB in water, d-FeOOH revealed to be a promising photocatalyst to be tested in the oxidation of emerging pollutants for the environmental decontamination

Comparison of methods for the detection of biofilm production in coagulase-negative staphylococci

<p>Abstract</p> <p>Background</p> <p>The ability of biofilm formation seems to play an essential role in the virulence of coagulase-negative staphylococci (CNS). The most clearly characterized component of staphylococcal biofilms is the polysaccharide intercellular adhesin (PIA) encoded by the <it>icaADBC </it>operon. Biofilm production was studied in 80 coagulase-negative staphylococci (CNS) strains isolated from clinical specimens of newborns with infection hospitalized at the Neonatal Unit of the University Hospital, Faculty of Medicine of Botucatu, and in 20 isolates obtained from the nares of healthy individuals without signs of infection. The objective was to compare three phenotypic methods with the detection of the <it>icaA</it>, <it>icaD </it>and <it>icaC </it>genes by PCR.</p> <p>Findings</p> <p>Among the 100 CNS isolates studied, 82% tested positive by PCR, 82% by the tube test, 81% by the TCP assay, and 73% by the CRA method. Using PCR as a reference, the tube test showed the best correlation with detection of the <it>ica </it>genes, presenting high sensitivity and specificity.</p> <p>Conclusions</p> <p>The tube adherence test can be indicated for the routine detection of biofilm production in CNS because of its easy application and low cost and because it guarantees reliable results with excellent sensitivity and specificity.</p

Physical, ecological and human dimensions of environmental change in Brazil's Pantanal wetland: Synthesis and research agenda

The Pantanal is the world's largest freshwater wetland, located in the geographical centre of South America. It is relatively well conserved, and features unique landscapes, ecosystems, and traditional cultural practices, shaped by the dynamic interaction of climatological, hydrological, geological, ecological, and anthropogenic factors. Its ecological integrity is increasingly threatened by human activities, particularly, in the wider catchment area, for example, deforestation, agricultural intensification, and construction of hydropower plants, with implications for local people's livelihoods. We present a synthesis of current literature on physical, ecological, and human dimensions of environmental change in the wetland, outline key research gaps, and discuss environmental management implications. The literature review suggests that better integration of insights from multiple disciplines is needed and that environmental management could be improved through a better grounding in traditional practices and local perspectives. We conclude with four recommendations: First, future environmental change research should build more strongly on the positive example of a small number of case studies where traditional and local knowledge of the environment was put into a dialogue with scientific knowledge and techniques. Second, we recommend a more explicit consideration of longer temporal scales (>10 years) in environmental change research, making use of oral and written histories, as well as palaeoecological techniques, to understand system responses to different magnitudes of human and climatic pressures, and ultimately, to inform future adaptation activities. Third, we suggest that enhanced stakeholder participation in conceiving and implementing research projects in the Pantanal would strengthen the practical relevance of research in addressing environmental management challenges, livelihood needs, and advocacy processes. Fourth, we call for a more systemic and integrative perspective on environmental education, which encompasses engagement activities between researchers, policy-makers, and citizens, to foster environmental awareness, scientific literacy, and public participation