No abstract

I In nf fl lu ue en nc ce e o of f b be ed d m me ed di ia a c ch ha ar ra ac ct te er ri is st ti ic cs s o on n a am mm mo on ni ia a a an nd d n ni it tr ra at te e r re em mo ov va al l i in n s sh ha al ll lo ow w h ho or ri iz zo on nt ta al l s su ub bs su ur rf fa ac ce e f fl lo ow w c co on ns st tr ru uc ct te ed d w we et tl la an nd ds s Abstract Two bed media were tested (gravel and Filtralite) in shallow horizontal subsurface flow (HSSF) constructed wetlands in order to evaluate the removal of ammonia and nitrate for different types of wastewater (acetate-based and domestic wastewater) and different COD/N ratios. The use of Filtralite allowed both higher mass removal rates (1.1 g NH4-N m −2 d −1 and 3 g NO3-N m −2 d −1 ) and removal efficiencies (>62% for ammonia, 90-100% for nitrate), in less than 2 weeks, when compared to the ones observed with gravel. The COD/N ratio seems to have no significant influence on nitrate removal and the removal of both ammonia and nitrate seems to have involved not only the conventional pathways of nitrificationdenitrification. The nitrogen loading rate of both ammonia (0.8-2.4 g NH4-N m −2 d −1 ) and nitrate (0.6-3.2 g NO3-N m −2 d −1 ) seem to have influenced the respective removal rates.

The proper design of DNA microarray experiments requires knowledge of biological and technical variation of the studied biological model. For the filamentous fungus Aspergillus niger, a fast, quantitative real-time PCR (qPCR)-based hierarchical experimental design was used to determine this variation. Analysis of variance components determined the contribution of each processing step to total variation: 68% is due to differences in day-to-day handling and processing, while the fermentor vessel, cDNA synthesis, and qPCR measurement each contributed equally to the remainder of variation. The global transcriptional response to D-xylose was analyzed using Affymetrix microarrays. Twenty-four statistically differentially expressed genes were identified. These encode enzymes required to degrade and metabolize D-xylose-containing polysaccharides, as well as complementary enzymes required to metabolize complex polymers likely present in the vicinity of D-xylosecontaining substrates. These results confirm previous findings that the D-xylose signal is interpreted by the fungus as the availability of a multitude of complex polysaccharides. Measurement of a limited number of transcripts in a defined experimental setup followed by analysis of variance components is a fast and reliable method to determine biological and technical variation present in qPCR and microarray studies. This approach provides important parameters for the experimental design of batch-grown filamentous cultures and facilitates the evaluation and interpretation of microarray data.Culturing filamentous organisms such as Aspergillus niger is difficult to reproduce compared to culturing unicellular organisms. Filamentous growth is characterized by the elongation and branching of hyphae, cylindrical cells that increase in length by growth at one end. De novo biosynthesis and active enzyme production occur mainly at the hyphal tips. In regions of distance from the tip, the hyphae age and become biologically less active (38). This hyphal growth is the result of adaption to the habitat of the organism, which enables it to spread over and penetrate surfaces and cross over nutrient-depleted gaps (6). However, under laboratory conditions, attachment of fungal mycelium to fermentor baffles and other extremities introduces heterogeneous growth that can be suppressed only to a certain extent (for instance, by cooling the fermentor headplate). The growing mycelium increases the culture broth viscosity, which reduces the mass transport of nutrients, oxygen, and heat, and affects the mixing characteristics in a fermentor or shake flask over time. Physical agitation and shear stress can cause uncontrolled breakage and fragmentation of the mycelia (37).Recent technologies such as global transcriptome analysis by DNA microarrays or quantitative real-time PCR (qPCR) require the use of replicate biological samples for high-quality data. Given the difficulties in culturing A. niger, obtaining transcript data without wasting resources requires proper experimental design. The k...

The capacity for physiological colour change has long been described in anuran amphibians. Camouflage against predators seems to be the most relevant function of dynamic changes in skin colour of frogs, but key aspects such as the rate at which these changes occur, or the specific colour components involved are not completely clear. Whereas most research on the topic has been reported on tree frogs in laboratory conditions, studies in other anurans or in the field are much scarcer. Here we show a potentially plastic, adaptive response in coloration of common midwife toads, Alytes obstetricans, from a population of central Portugal, whose pigmentation varied with their natural backgrounds. Using quantitative image analysis, we compared hue, saturation and brightness of dorsal skin coloration of toads and the colour of the area of ground immediately around them. We found a positive correlation between coloration of toads and background colour for the three components of the colour. As well as other anuran species, A. obstetricans might adjust skin coloration to match the surrounding environment, thus benefitting from short-term reversible crypsis strategies against predators. A less supported hypothesis would be that toads accurately select matching backgrounds to improve concealment as an antipredatory strategy.