Small is better: comparing the efficiency of two Surber samplers' sizes for biomonitoring programs in tropical headwater streams in the Amazon region.

This study aimed to compare the efficiency of two different sizes of the Surber sampler to assess benthic macroinvertebrates in headwater streams in two Amazonian regions. Two Surber samplers of different sizes were used, one measuring 20 × 20 cm and the other 30 × 30 cm, both with a 0.25-mm net. The number of replicates taken was 6 for the smaller sampler and 3 for the bigger one, maintaining approximately the same total sampled area. The study was carried out in 12 headwater streams with different environmental conditions. Biological metrics were calculated for each size at each site and compared within each stream health category. A two-way analysis of similarities test was performed to compare the community structure assessed by each method at each stream. A normalized sampling effort was used to quantify the number of samples required to correctly sample each site. The data did not show a significant difference between the two sizes regarding the taxonomic recruitment and the community structure sampled at each stream, but differences were found between the two sizes in dominance values and in Shannon index scores for the natural sites. Furthermore, the smaller Surber was able to assess 70% of the estimated richness in all sites, which suggests that it is better to assess benthic macroinvertebrates than the larger Surber. Moreover, the smaller Surber is easier to transport in the field, reducing the effort of the technician, and takes less time to sort the material collected with it, which can reduce the sample processing effort, therefore reducing the cost of the project.

Acute toxicity bioassay with the amphipod, Grandidierella bonnieroides S. after exposure to sediments from an urban estuary (Macaé River Estuary, RJ, Brazil).

Acute toxicity to Grandidierella bonnieroides and physicochemical analysis were used for quality assessment of the sediment of the Macaé River urban estuary, located in the Brazilian coast where rapid socioeconomic growth has been induced by offshore oil and gas exploration at the Campos Basin. Sediment samples were collected during four events in four sampling sites of the estuary and also in a control site. Organism mortality after exposure to the estuarine sediments was, on average, 30 % a value higher than in the control site where it was 10 %. This result together with the physicochemical analysis suggests an initial toxicity condition of the sediments from this aquatic coastal environment.

Species identity and diversity effects on invasion resistance of tropical freshwater plant communities.

Biotic resistance mediated by native plant diversity has long been hypothesized to reduce the success of invading plant species in terrestrial systems in temperate regions. However, still little is known about the mechanisms driving invasion patterns in other biomes or latitudes. We help to fill this gap by investigating how native plant community presence and diversity, and the presence of native phylogenetically closely related species to an invader, would affect invader Hydrilla verticillata establishment success in tropical freshwater submerged plant communities. The presence of a native community suppressed the growth of H. verticillata, but did not prevent its colonisation. Invader growth was negatively affected by native plant productivity, but independent of native species richness and phylogenetic relatedness to the invader. Native plant production was not related to native species richness in our study. We show that resistance in these tropical aquatic submerged plant communities is mainly driven by the presence and biomass of a native community independent of native species diversity. Our study illustrates that resistance provided by these tropical freshwater submerged plant communities to invasive species contrasts to resistance described for other ecosystems. This emphasizes the need to include understudied systems when predicting patterns of species invasiveness and ecosystem invasibility across biomes.

Global regulation of methane emission from natural lakes.

Methane (CH4) emissions from lakes are the largest of the emissions from freshwater ecosystems. We compile open water CH4 emission estimates from individual lakes from all over the world and consider the three main emission pathways: diffusive; ebullitive; and storage. The relationships between emissions, environmental variables, lake characteristics and methodological approaches are investigated for the measurements from 297 lakes. We show that environmental factors, such as temperature and precipitation, act as important driving factors for CH4 emissions, with higher emissions occurring where air temperature and precipitation are high. The diffusive flux of CH4 was found to be positively related to dissolved organic carbon concentration. Diffusive flux is the most frequently estimated component of the total flux, while the other emission pathways are often neglected. Based on the cases where all three components of the total flux were measured (30 lakes), we estimate that measuring the diffusive emission only, and then assuming that the value obtained is a good surrogate for the total emission, would have led to a 277% underestimation of the real total flux. In addition we show that the estimation of fluxes is method-dependent with substantial differences revealed between the flux estimates obtained from different measurement techniques. Some of this uncertainty is due to technical constraints which should not be neglected, and lake CH4 flux measurement techniques require thorough re-evaluation.

Detection of multidrug-resistant Enterobacteriaceae isolated from river waters flowing to the Guanabara Bay and from clinical samples of hospitals in Rio de Janeiro, Brazil / Detección de enterobacterias multirresistentes aisladas en aguas de los ríos que desembocan en la bahía de Guanabara y en muestras de hospitales de Río de Janeiro, Brasil

INTRODUCTION: The use of antibiotics in humans, animal husbandry and veterinary activities induces selective pressure leading to the colonization and infection by resistant strains. OBJECTIVE: We evaluated water samples collected from rivers of the Guanabara Bay, which have suffered minor and major environmental degradation, and clinical samples of hospital origin to detect evidence of the presence of resistance genes to aminoglycosides, beta-lactam antibiotics and fluoroquinolones in strains of Klebsiella pneumoniae subsp. pneumoniae, K. pneumoniae subsp. ozaenae and Escherichia coli. MATERIALS AND METHODS: For isolation of the water strains we employed culture media containing 32 µg/ml cephalotin and 8 µg/ml gentamicin. The strains from clinical materials were selected using culture media containing 8 µg/ml gentamicin. The strains were identified and subjected to antimicrobial susceptibility testing (AST), plasmid DNA extraction and polymerase chain reaction (PCR) to detect genes encoding enzymes modifying aminoglycosides (EMA), extended-spectrum beta-lactamases (ESBL) and plasmid mechanisms of quinolone resistance (PMQR). RESULTS: The AST of the isolates recovered from water samples showed multidrugresistance profiles similar to those found in isolates recovered from clinical materials. All isolates from water samples and 90% of the isolates from clinical samples showed at least one plasmid band. In the PCR assays, 7.4% of the isolates recovered from water samples and 20% of those from clinical materials showed amplification products for the three antimicrobial classes. CONCLUSION: We believe that the detection of microorganisms presenting genetic elements in environments such as water is necessary for the prevention and control of their dissemination with potential to infect humans and other animals in eventual contact with these environments.

Introducción. El uso de antibióticos en seres humanos, en la industria pecuaria y en las actividades veterinarias induce una presión selectiva que resulta en la colonización e infección con cepas resistentes. Objetivo. Determinar la presencia de genes de resistencia a aminoglucósidos, betalactámicos y fluoroquinolonas en cepas de Klebsiella pneumoniae subsp. pneumoniae, K. pneumoniae subsp. ozaenae y Escherichia coli, obtenidas de muestras de agua de los ríos que desembocan en la bahía de Guanabara y de muestras clínicas de hospitales de Río de Janeiro. Materiales y métodos. En la selección de las cepas resistentes obtenidas de las muestras de agua de los ríos, se emplearon medios de cultivo que contenían 32 µg/ml de cefalotina y 8 µg/ml de gentamicina. En el caso de las muestras de especímenes clínicos, se usaron medios de cultivo que contenían 8 µg/ml de gentamicina. Las cepas se identificaron y se sometieron a pruebas de sensibilidad antimicrobiana, extracción de ADN plasmídico y pruebas de reacción en cadena de la polimerasa (PCR) para detectar los genes que codifican aquellas enzimas que modifican los aminoglucósidos, las betalactamasas de espectro extendido (BLEE) y los mecanismos de resistencia a las quinolonas mediados por plásmidos. Resultados. Se encontraron perfiles de resistencia a los antimicrobianos similares en los dos grupos. En todas las bacterias obtenidas de las muestras de agua y en 90 % de las muestras clínicas, se evidenciaron bandas de plásmidos asociados con la transferencia de genes de resistencia. En las pruebas de PCR, se obtuvieron productos de amplificación de los genes de resistencia para las tres clases de antimicrobianos analizados, en el 7,4 % de las bacterias recuperadas de las muestras de agua y en el 20 % de aquellas recuperadas de las muestras clínicas. Conclusión. La detección de microorganismos con elementos genéticos que confieren resistencia a los antibióticos en ambientes como el agua, es una estrategia necesaria para prevenir y controlar la diseminación de estos agentes patógenos con potencial para infectar a humanos y a otros animales en dichos ambientes.

Nitric Oxide Production Inhibition and Anti-Mycobacterial Activity of Extracts and Halogenated Sesquiterpenes from the Brazilian Red Alga Laurencia Dendroidea J. Agardh.

BACKGROUND: Red algae of the genus Laurencia J. V. Lamouroux are a rich source of secondary metabolites with important pharmacological activities such as anti-tumoral, anti-inflammatory, anti-fungal, anti-viral, anti-leishmanial, anti-helminthic, anti-malarial, anti-trypanosomal, anti-microbial as well as anti-bacterial against Mycobacterium tuberculosis. OBJECTIVE: In the present study, we evaluated the inhibition of nitric oxide (NO) and tumor necrosis factor-α production and the anti-mycobacterial activity of crude extracts from the red Alga Laurencia dendroidea (from the South-Eastern coast of Brazil). Halogenated sesquiterpenes elatol (1), obtusol (2) and cartilagineol (3), previously isolated from this Alga by our group, were also studied. MATERIALS AND METHODS: The lipopolysaccharide-activated macrophage cells (RAW 264.7) were used as inflammation model. Cytotoxic effect was determined using a commercial lactate dehydrogenase (LDH) kit and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The growing Mycobacterium inhibition was verified against Mycobacterium bovis Bacillus Calmette-Guérin and M. tuberculosis H37 Rv strains. RESULTS: The crude extract from Alga collected at Angra dos Reis, RJ, Brazil, was the most active inhibitor of both mycobacterial growth (half maximal inhibitory concentration [IC50] 8.7 ± 1.4 µg/mL) and NO production by activated macrophages (IC50 5.3 ± 1.3 µg/mL). The assays with isolated compounds revealed the anti-mycobacterial activity of obtusol (2), whereas (-)-elatol (1) inhibited the release of inflammatory mediators, especially NO. To our knowledge, this is the first report describing an anti-mycobacterial effect of L. dendroidea extract and demonstrating the association of this activity with obtusol (2). CONCLUSION: The described effects of active compounds from L. dendroidea are promising for the control of inflammation in infectious diseases and specifically, against mycobacterial infections associated with exacerbated inflammation. SUMMARY: Inflammation is strongly involved in the pathogenesis of most infectious diseases, including TB. The treatment of TB is based on the use of anti mycobacterial drugs, however the most severe forms of TB, require additional anti inflammatory therapy to prevent excessive inflammation. A combination of these properties in one compound could provide additional therapeutic benefits. In this work, we studied L. dendroidea extracts and purified compounds and demonstrated that the LDA extract and (-)-elatol (1) were potent in inhibiting NO production by macrophages through the specific inhibition of iNOS expression. The LDA and LDM extracts and obtusol (2) were active against virulent strain of M. tuberculosis. This is the first report demonstrating that the anti-inflammatory activities of L. dendroidea were associated with the presence of (-)-elatol (1), whereas anti-mycobacterial activities of L. dendroidea extracts were associated with obtusol (2).