Grasping the heterogeneity of kettle hole water quality in Northeast Germany

Riparian vegetation typically provides substantial allochthonous material to aquatic ecosystems where micro-organisms can play an important role in organic matter degradation which can support consumer biomass. We examined the effects of leaf litter quality (e.g., leaf nutrients, lignin and cellulose content), leaf species mixing, and microbial community diversity on in-stream breakdown rates of litter from dominant riparian trees (Melaleuca argentea, M. leucadendra, and Nauclea orientalis) in both a perennial and intermittent river in Australia’s wet-dry tropics. Leaf mass remaining after 82 days of in-stream incubation was negatively correlated (P < 0.05) with initial leaf N and P content while initial lignin and cellulose content had no statistically significant effect. Breakdown rates of incubated leaves of both Melaleuca and Nauclea were significantly higher in mixed litter bags compared with single species litter bags. Although it was expected that leaf N content would decrease from initial levels during decomposition, we found either similar or slightly higher N content following in-stream incubation suggesting microbial colonisation increased overall N content. Stable isotopes of δ¹³C and δ¹⁵N for the major sources and consumers in both rivers provide evidence that leaf litter was an important macroinvertebrate food source in the perennial river where heavy shading may limit algal production. However, in the intermittent river where riparian cover was low, benthic algae were the major organic carbon source for consumers. Our findings suggest that riparian tree species influence rates of in-stream organic matter processing, microbial community composition, and aquatic food web dynamics in tropical wet-dry streams.     

Cultivating <Emphasis Type="Italic">in vitro</Emphasis> coconut palms (<Emphasis Type="Italic">Cocos nucifera</Emphasis>) under glasshouse conditions with natural light,improves <Emphasis Type="Italic">in vitro</Emphasis> photosynthesis nursery survival and growth

Plantlets of coconut were cultured in vitro under three different ambient conditions including a standard culture room, a culture room inside a glasshouse with natural light but controlled temperature, and a standard glasshouse with natural light and natural fluctuations of temperature. Plantlets from the 3 treatments were compared in terms of growth, plant survival as well as net photosynthesis and efficiency of PSII (Fv/Fm ratio) both at the end of the in vitro stage and at 3 stages of ex vitro acclimatization. At the end of the in vitro stage, plantlets cultured in vitro under glasshouse conditions showed the best performance showing the highest photosynthesis rate, dry weight and number of leaves. Plantlets from the standard culture room showed the lowest photosynthesis and growth rate. After 6 months of ex vitro acclimatization, plantlets originally grown in vitro under glasshouse conditions maintained better field survival and growth rates in terms of fresh weight, dry weight and leaf number than plantlets originally grown in vitro in the standard culture room. Although more studies are required to define the reason for this effect, it is clear that the conditions of standard culture rooms are not the best for in vitro cultivation of coconut and perhaps other tropical species.     

Autohydrolysis Pretreatment of Mixed Softwood to Produce Value Prior to Combustion

Autohydrolysis is a hot water pretreatment to extract soluble components from wood that can be used prior to converting the woody residuals into paper, wood products, fuel, or other goods. In this study, mixed softwood chips were autohydrolyzed in hot water at 150, 160, 170, and 180 °C for 1 and 2 h residence times. The objective was to understand the tradeoff between the extraction of fermentable sugar and the residual solid total energy of combustion quantitatively. This process strategy will be referred to as “value prior to combustion”. High-performance liquid chromatography was used to determine chemical compositions (sugars and byproducts such as acetic acid, furfural, and hydroxymethylfurfural) of the extracted liquid and residuals; a bomb calorimeter was used to measure the heating value of original wood and solid residue. As the autohydrolysis temperature increased, material balances of the system indicated higher volatile byproducts loss. More hemicelluloses were solubilized by the hot water extraction process at higher temperatures and longer residence times, and a greater degree of sugar degradation was also observed. The maximum sugar yield was determined to occur at conditions of 170 °C for 2 h, during which 13 g of sugar was recovered from the extract out of 100 g of oven-dried wood. The heating value of the solid residues after extraction was greater than the original wood. The total energy content of the solid residual after extraction ranged from 85 to 98 % of the original energy content of the feed with higher temperatures reducing the total energy content.     

Galactose/N-acetylgalactosamine lectin: The coordinator of host cell killing

Entamoeba histolytica is an enteric parasite that can kill host cells via a contact-dependent mechanism. This killing involves the amoebic surface protein referred to as the Gal/GalNAc lectin. The Gal/GalNAc lectin binds galactose and N-acetylgalactosamine allowing the adherence of amoebas to host cells. Involvement of the lectin in the pathogenesis ofE. histolytica infection will be reviewed in this paper. The lectin has been shown to have very specific and substantial effects on adherence, cytotoxicity, and encystation. There is also possible involvement of the lectin in phagocytosis and caspase activation in host cells.     

Enzymatic characterization of Catalase from Bacillus anthracis and prediction of critical residues using information theoretic measure of Relative Entropy

In order to cope up with the reactive oxygen species (ROS) generated by host innate immune response, most of the intracellular organisms express Catalase for the enzymatic destruction/detoxification of hydrogen peroxide, to combat its deleterious effects. Catalase thus, scavenges ROS thereby playing a pivotal role in facilitating the survival of the pathogen within the host, and thus contributes to its pathogenesis. Bacillus anthracis harbors five isoforms of Catalase, but none of them has been studied so far. Thus, this study is the first attempt to delineate the biochemical and functional characteristics of one of the isoforms of Catalase (Cat1.4) of B. anthracis, followed by identification of residues critical for catalysis. The general strategy used, so far for mutational analysis in Catalases is structure based, i.e. the residues in the vicinity of heme were mutated to decipher the enzymatic mechanism. However, in the present study, protein sequence analysis was used for the prediction of catalytically important residues of Catalase. Essential measures were adopted to ensure the accuracy of predictions like after retrieval of well-annotated sequences from the database with EC 1.11.1.6, preprocessing was done to remove irrelevant sequences. The method used for multiple alignment of sequences, was guided by structural alignment and thereafter, an information theoretic measure, Relative Entropy was used for the critical residue prediction. By exploiting this strategy, we identified two previously known essential residues, H55 and Y338 in the active site which were demonstrated to be crucial for the activity. We also identified six novel crucial residues (Q332, Y117, H215, W257, N376 and H146) located distantly from the active site. Thus, the present study highlights the significance of this methodology to identify not only those crucial residues which lie in the active site of Catalase, but also the residues located distantly.     

Deep brain stimulation

During the last decade deep brain stimulation (DBS) has become a routine method for the treatment of advanced Parkinsons disease (PD), leading to striking improvements in motor function and quality of life of PD patients. It is associated with minimal morbidity. The rationale of targeting specific structures within basal ganglia such as the subthalamic nucleus (STN) or the internal segment of the globus pallidus (GPi) is strongly supported by the current knowledge of the basal ganglia pathophysiology, which is derived from extensive experimental work and which provides the theoretical basis for surgical therapy in PD. In particular, the STN has advanced to the worldwide most used target for DBS in the treatment of PD, due to the marked improvement of all cardinal symptoms of the disease. Moreover on-period dyskinesias are reduced in parallel with a marked reduction of the equivalent daily levodopa dose following STN–DBS. The success of the therapy largely depends on the selection of the appropriate candidate patients and on the precise implantation of the stimulation electrode, which necessitates careful imaging-based pre-targeting and extensive electrophysiological exploration of the target area. Despite the clinical success of the therapy, the fundamental mechanisms of high-frequency stimulation are still not fully elucidated. There is a large amount of evidence from experimental and clinical data that stimulation frequency represents a key factor with respect to clinical effect of DBS. Interestingly, high-frequency stimulation mimics the functional effects of ablation in various brain structures. The main hypotheses for the mechanism of high-frequency stimulation are: (1) depolarization blocking of neuronal transmission through inactivation of voltage dependent ion-channels, (2) jamming of information by imposing an efferent stimulation-driven high-frequency pattern, (3) synaptic inhibition by stimulation of inhibitory afferents to the target nucleus, (4) synaptic failure by stimulation-induced neurotransmitter depletion. As the hyperactivity of the STN is considered a functional hallmark of PD and as there is experimental evidence for STN-mediated glutamatergic excitotoxicity on neurons of the substantia nigra pars compacta (SNc), STN–DBS might reduce glutamatergic drive, leading to neuroprotection. Further studies will be needed to elucidate if STN–DBS indeed provides a slow-down of disease progression.     

Belowground carbon cycling in a humid tropical forest decreases with fertilization

Only a small fraction of the carbon (C) allocated belowground by trees is retained by soils in long-lived, decay-resistant forms, yet because of the large magnitude of terrestrial primary productivity, even small changes in C allocation or retention can alter terrestrial C storage. The humid tropics exert a disproportionately large influence over terrestrial C storage, but C allocation and belowground retention in these ecosystems remain poorly quantified. Using mass balance and ¹³C isotope methods, we examined the effects of afforestation and fertilization, two land-use changes of large-scale importance, on belowground C cycling at a humid tropical site in Hawaii. Here we report that in unfertilized plots, 80% of the C allocated belowground by trees to roots and mycorrhizae was returned to the atmosphere within 1 year; 9% of the belowground C flux was retained in coarse roots and 11% was retained as new soil C. The gains in new soil C were offset entirely by losses of old soil C. Further, while fertilization early in stand development increased C storage in the litter layer and in coarse roots, it reduced by 22% the flux of C moving through roots and mycorrhizae into mineral soils. Because soil C formation rates related strongly to rhizosphere C flux, fertilization may reduce an already limited capacity of these forests to sequester decay-resistant soil C.     

Enhanced iturin A production by <Emphasis Type="Italic">Bacillus subtilis</Emphasis> and its effect on suppression of the plant pathogen <Emphasis Type="Italic">Rhizoctonia solani</Emphasis>

The behavior of Streptomyces peucetius var. caesius N47 was studied in a glucose limited chemostat with a complex cultivation medium. The steady-state study yielded the characteristic constants μ _max over 0.10 h⁻¹, Y _XS 0.536 g g⁻¹, and m_S 0.54 mg g⁻¹ h⁻¹. The product of secondary metabolism, ɛ-rhodomycinone, was produced with characteristics Y _PX 12.99 mg g⁻¹ and m _P 1.20 mg g⁻¹ h⁻¹. Significant correlations were found for phosphate and glucose consumption with biomass and ɛ-rhodomycinone production. Metabolic flux analysis was conducted to estimate intracellular fluxes at different dilution rates. TCA, PPP, and shikimate pathway fluxes exhibited bigger values with production than with growth. Environmental perturbation experiments with temperature, airflow, and pH changes on a steady-state chemostat implied that an elevation of pH could be the most effective way to shift the cells from growing to producing, as the pH change induced the biggest transient increase to the calculated ɛ-rhodomycinone flux.