Two fish species, one top predator
and one intermediate detritivorous species
, were experimentally manipulated to evaluate their relative importance in structuring the periphytic community, as well as their effects on the other trophic levels. An enclosure experiment was conducted in the Potreirinho creek, a second order tributary of Paranapanema River, SE Brazil. Five treatments were used: enclosure of the predator species, enclosure of the detritivorous species, enclosure of both together, exclusion of all fish species (closed control cage), and cage open to all fish community (open control). Through direct and indirect effects,
, when alone, gave rise to a trophic cascade that resulted in a positive effect on algal resources. Through direct effects,
, when alone, reduced the amount of organic matter, resulting in a positive indirect effect on algae. In addition, when the two species were enclosed together, only the effects determined by the detritivorous species were present. The results indicate the important role of the intermediate detritivorous species in the maintenance of the composition and trophic structure of the analyzed community by reducing the effects caused by the top predator.
Two wheat genotypes were grown in hydroponic culture, containing 4 mM KNO3, NH4Cl and NH4NO3. Activities of N metabolizing enzymes, aminotransferases, carbohydrate and TCA cycle enzymes were analyzed along with protein, amino acid, N, sugar content and growth parameters in shoot and root. After 12 days, the size of shoot and root system decreased significantly when plants were supplied with NH4Cl as exclusive N source. Under NH4NO3 growth parameters, N and carbon metabolism were elevated as compared to NH4Cl but less than KNO3 source indicating inhibition of NH4+ toxicity by NO3− uptake. Our results suggested that GDH, aminotransferases and PEPC play an important role in ammonium detoxification by its incorporation into amino acids. Thus, the morphologic differences among plants growing in NH4+ or NO3− nutrition confirm the hypothesis that N source determines the growth habit of plant in wheat by modulating the endogenous levels of protein and sugar content.
Authors:Bosede Titilope Bamigboye, Olugbenga Adekunle Olowe, and Samuel Sunday Taiwo
, designated vancomycin intermediate-resistant S. aureus (VISA), is associated with a thickened and poorly cross-linked cell wall, resulting in accumulation of acyl- d -alanyl- d -alanine (X- d -Ala- d -Ala) targets at the periphery of the cell that sequester
Authors:Oreva Ogbor, Abraham Ajayi, Andreas E. Zautner, and Stella I. Smith
%), chloramphenicol 8/8 (100%), cloxacillin 8/8 (100%), and streptomycin 8/8 (100%). Five (62.5%) of the isolates showed decreased susceptibility (i.e., were intermediate tested) to erythromycin. Seven (87.5%) of the isolates showed susceptibility to amoxicillin
Authors:Maha Refaey, Nóra Kováts, Á. Kárpáti, and P. Thury
Whole effluent toxicity is most often considered as a static parameter. However, toxicity might change as degradation processes, especially biodegradation goes by and intermediate products appear. These intermediates can even be more toxic than the original effluent was, posing higher risk to the ecosystem of the recipient water body. In our test series it was assessed how toxicity of a municipal wastewater sample changes during biodegradation taking into consideration different temperature regimes (10, 20 and 30 °C). Results proved our null hypothesis: after the high initial toxicity of the fresh effluent sample toxicity did show a further increase. Biodegradation resulted in toxicity reduction only after an approx. 2 week-period.
This study describes plant species diversity in well preserved dry coastal dune systems along the southern Baltic coast. Variations in diversity and in distributional character of plant species and plant communities throughout the study areas result mainly because of the interplay between plant succession, exposure, disturbance and resource availability. Environmental indicator values, used to describe dynamics in dune habitats, show a decline of light and temperature with increased distance to the sea, accompanied by higher soil moisture due to accumulation of organic matter. Species richness and species diversity showed a humped-shaped curve along a coast-to-inland gradient. The highest species richness of vascular plants and cryptogamic species were found in plant communities of grey dunes at intermediate levels of environmental and disturbance gradients, which confirms the intermediate disturbance theory.