Structure and dynamics of phytoplankton in an Amazon lake, Brazil

Natural lake systems represent important reservoirs for residential water supply, fish production, recreational activities and enjoyment of their natural beauty. Nevertheless, human impacts may affect their health status resulting in degradation and loss of biodiversity. The aim of the present study was to obtain data on the health status of a natural lake located in an indigenous reservation in the Brazilian Amazon, using the phytoplankton community changes along the rainy (June) and dry (November) seasons of 2006. We collected water (temperature, pH, Secchi depth and conductivity) and phytoplankton samples from the subsurface, middle of the water column, and approximately 30 cm above the bottom, over 24-hour sampling periods, from a central station in the lake. Samples taken from biotic and abiotic variables were correlated using canonical correspondence analysis (CCA). Results showed that the lake exhibited high temperatures in both seasons, and showed thermal stratification only during the rainy season. Dissolved oxygen exhibited a clinograde pattern in the rainy season and high oxygen in the hypolimnion in the dry season. In the rainy season, the water near the bottom was acidic, turbid and had a greater concentration of phosphorus. Dissolved oxygen, conductivity, pH, nitrite, total phosphorus and total dissolved phosphorus exhibited diel variations in the rainy season, whereas water temperature, dissolved oxygen, total nitrogen and total dissolved phosphorus exhibited significant differences between hours of the day in the dry season. The phytoplankton was represented by 39 taxa, and Chlorophyta showed the greatest species richness, totaling 25 taxa. Among Chlorophyta, desmids were the most diverse, accounting 52%. Bacillariophyta (nine species) was the second most diverse group. Cyanophyta was represented by three species, including Merismopedia tenuissima, the most abundant taxon. Despite the occurrence of taxa that indicate organic pollution, their biomass and frequency indicate that the system is not currently threatened. Lake Caracaran? is an oligotrophic system, with low algal density and isolated blooming episodes due to its shallow depth.     

Field biology of Edessa rufomarginata (Hemiptera: Pentatomidae): phenology, behavior, and patterns of host plant use

Pentatomids may cause direct and indirect damage to important crop plants. Biological and ecological features of phytophagous stink bugs in natural environments, however, remain poorly documented. Here, we provide an ecological account of Edessa rufomarginata De Geer on Caryocar brasiliense (Caryocaraceae) in the Brazilian savanna. The phenology of E. rufomarginata matched that of its host plant, with immatures developing in the wet season simultaneously with the production of vegetative and reproductive plant tissue. Females do not exhibit parental care and lay eggs more frequently on larger plants. Oviposition frequency, however, does not differ between plants with and without flowers/fruits. Nymphs and adults usually feed on stem parts and more rarely on flower buds and fruits. First- and second-instar nymphs remain aggregated, but disperse as third-instar nymphs. Adults and nymphs were more abundant on mature stems of C. brasiliense compared with other plant locations. Ants visiting the plant to search for extrafloral nectar occasionally tap the abdomen of E. rufomarginata nymphs with their antennae to obtain honeydew. This is the first record of trophobiotic interactions between Edessa stinkbugs and ants, and one of the few for heteropterans. The interaction of the stink bug with other natural enemies, such as predaceous Heniartes (Reduviidae), was also observed. Given the pest status of Edessa species for crop plants, additional field studies on host plants, interaction with ants, and natural enemies in native habitats are needed for an effective management of these stink bugs in tropical agricultural systems.     

<Emphasis Type="Italic">Candida albicans</Emphasis> virulence and drug-resistance requires the <Emphasis Type="Italic">O</Emphasis>-acyltransferase Gup1p

Background  

GUP1 gene was primarily identified in Saccharomyces cerevisiae being connected with glycerol uptake defects in association with osmotic stress response. Soon after, Gup1p was implicated in a complex and extensive series of phenotypes involving major cellular processes. These include membrane and wall maintenance, lipid composition, bud-site selection, cytoskeleton orientation, vacuole morphology, secretory/endocytic pathway, GPI anchors remodelling, and lipid-ordered domains assembly, which is compatible with their inclusion in the Membrane Bound O-acyl transferases (MBOAT) family. In mammals, it has been described as a negative regulator of the Sonic hedgehog pathway involved in morphogenesis, differentiation, proliferation, among other processes.     

Global gene expression under nitrogen starvation in <Emphasis Type="Italic">Xylella fastidiosa</Emphasis>: contribution of the σ<Superscript>54</Superscript> regulon

Background  

Xylella fastidiosa, a Gram-negative fastidious bacterium, grows in the xylem of several plants causing diseases such as citrus variegated chlorosis. As the xylem sap contains low concentrations of amino acids and other compounds, X. fastidiosa needs to cope with nitrogen limitation in its natural habitat.     

Automated assay for screening the enzymatic release of reducing sugars from micronized biomass

Background  

To reduce the production cost of bioethanol obtained from fermentation of the sugars provided by degradation of lignocellulosic biomass (i.e., second generation bioethanol), it is necessary to screen for new enzymes endowed with more efficient biomass degrading properties. This demands the set-up of high-throughput screening methods. Several methods have been devised all using microplates in the industrial SBS format. Although this size reduction and standardization has greatly improved the screening process, the published methods comprise one or more manual steps that seriously decrease throughput. Therefore, we worked to devise a screening method devoid of any manual steps.     

Extracellular <Emphasis Type="Italic">Paracoccidioides brasiliensis</Emphasis> phospholipase B involvement in alveolar macrophage interaction

Background  

Phospholipase B (PLB) has been reported to be one of the virulence factors for human pathogenic fungi and has also been described as necessary for the early events in infection. Based on these data, we investigated the role of PLB in virulence and modulation of the alveolar pulmonary immune response during infection using an in-vitro model of host-pathogen interaction, i.e. Paracoccidioides brasiliensis yeast cells infecting alveolar macrophage (MH-S) cells.     

A rational use of glucocorticoids in patients with early arthritis has a minimal impact on bone mass

Introduction  

Glucocorticoid (GC)-induced osteoporosis is a frequent complication in patients with rheumatoid arthritis. However, little information exists about the consequences of GC use in patients with early arthritis. Here we describe the variables underlying the use of GC in early arthritis, as well as its effect on bone-mineral density.     

Quality of different aphids species as hosts for the parasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae: Aphidiinae)

The suitability of Macrosiphum euphorbiae (Thomas), Aulacorthum solani (Kaltenbach) and Acyrthosiphon kondoi Shinji (Hemiptera: Aphididae) as hosts for the aphid parasitoid Aphidius ervi Haliday was evaluated by assessing host size, host preference, and host quality. Tests were carried out in an environmental chamber at 22±1oC, 70±10% RH and 12h photophase. Replicates (11) consisted of one 24h-old mated female of A. ervi without a previous oviposition experience. Female was released into a Petri dish (5 cm) with 20 2nd and 3rd instars of one of each aphid species tested on a leaf disc of the host plant onto a 1% water-agar layer. Parasitoid emergency was lower in A. kondoi (78.7%) compared to M. euphorbiae (92.2%) and A. solani (91.7%). Acyrthosiphon kondoi (0.36 mm) was the smallest host. The parasitoid showed preference (74.0% parasitism) for M. euphorbiae, the largest host (hind tibia length=0.73 mm), which in turn yielded larger A. ervi females (0.75 mm).