The effects of two abundant ant species on soil nutrients and seedling recruitment in Brazilian Atlantic Forest

Ants can influence soil fertility and the spatial distribution of seeds, with possible effects on seedling recruitment. The ant species Pachycondyla striata Fr. Smith, 1858 and Odontomachus chelifer (Latreille, 1802) co-occur in many forest areas in the Neotropics. We assessed soil fertility and seed bank structure in soil samples close and distant (control) from ant nests in forest fragments. We also assessed the richness and abundance of seedlings on nests and control sites. In soil samples from ant nests, the concentration of phosphorus and potassium were respectively 55.6% and 36% higher than in control sites. Aluminium was 11–15% lower in soil samples from ant nests. In the greenhouse, soils from ant nests had higher plant abundance and species richness, but the same species composition in comparison with control sites. Although more plants emerged from soil samples of O. chelifer nests, in the field, the density and richness of seedlings were similar for the two ant species studied. Seedlings in the nest sites were, on average, 1.8 times more abundant and 1.6 times richer in species than in control sites. Our results showed that ant species can play a key role in seedling recruitment in forest fragments, where other animals with equivalent and positive effects, such as mammals, are missing.     

Diversity of bacteriocins in the microbiome of the Tucuruí Hydroelectric Power Plant water reservoir and three-dimensional structure prediction of a zoocin

Bacteriocins are antimicrobial peptides expressed by bacteria through ribosomal activity. In this study, we analyzed the diversity of bacteriocin-like genes in the Tucuruí-HPP using a whole-metagenome shotgun sequencing approach. Three layers of the water column were analyzed (photic, aphotic and sediment). Detection of bacteriocin-like genes was performed with blastx using the BAGEL4 database as subject sequences. In order to calculate the abundance of bacteriocin-like genes we also determined the number of 16S rRNA genes using blastn. Taxonomic analysis was performed using RAST server and the metagenome was assembled using IDBA-UD in order to recover the full sequence of a zoocin which had its three-dimensional structure determined. The photic zone presented the highest number of reads affiliated to bacteriocins. The most abundant bacteriocins were sonorensin, Klebicin D , pyocin and colicin. The zoocin model was composed of eight anti-parallel β-sheets and two α-helices with a Zn²⁺ ion in the active site. This model was considerably stable during 10 ns of molecular dynamics simulation. We observed a high diversity of bacteriocins in the Tucuruí-HPP, demonstrating that the environment is an inexhaustible source for prospecting these molecules. Finally, the zoocin model can be used for further studies of substrate binding and molecular mechanisms involving peptidoglycan degradation.     

Gene Expression Studies in Formalin-Fixed Paraffin-Embedded Samples of Cutaneous Cancer: The Need for Reference Genes

Formalin-fixed paraffin-embedded (FFPE) tumour samples may provide crucial data regarding biomarkers for neoplasm progression. Analysis of gene expression is frequently used for this purpose. Therefore, mRNA expression needs to be normalized through comparison to reference genes. In this study, we establish which of the usually reported reference genes is the most reliable one in cutaneous malignant melanoma (MM) and cutaneous squamous cell carcinoma (CSCC). ACTB, TFRC, HPRT1 and TBP expression was quantified in 123 FFPE samples (74 MM and 49 CSCC biopsies) using qPCR. Expression stability was analysed by NormFinder and Bestkeeper softwares, and the direct comparison method between means and SD. The in-silico analysis with BestKeeper indicated that HPRT1 was more stable than ACTB and TFRC in MM (1.85 vs. 2.15) and CSCC tissues (2.09 vs. 2.33). The best option to NormFinder was ACTB gene (0.56) in MM and TFRC (0.26) in CSCC. The direct comparison method showed lower SD means of ACTB expression in MM (1.17) and TFRC expression in CSCC samples (1.00). When analysing the combination of two reference genes for improving stability, NormFinder indicated HPRT1 and ACTB to be the best for MM samples, and HPRT1 and TFRC genes for CSCC. In conclusion, HPRT1 and ACTB genes in combination are the most appropriate choice for normalization in gene expression studies in MM FFPE tissue, while the combination of HPRT1 and TFRC genes are the best option in analysing CSCC FFPE samples. These may be used consistently in forthcoming studies on gene expression in both tumours.     

Interleukin-2 (IL-2) receptor-betagamma signalling is activated by c-Kit in the absence of IL-2, or by exogenous IL-2 via JAK3/STAT5 in human papillomavirus-associated cervical cancer

Activation of the interleukin-2 receptor (IL-2R) induces signalling cascades promoting T cell proliferation. However, signal transduction pathways triggered in IL-2R-expressing solid tumours are unknown. This report shows that human papillomavirus (HPV)-associated cervical cancer cells express an IL-2R composed of beta and gamma chains (IL-2Rbetagamma), and that IL-2-mediated activation increases the phosphorylation of JAK3 and STAT5, stimulating cell proliferation. Interestingly, endogenous IL-2 is not produced by these cells, suggesting the activation of IL-2Rbetagamma by an alternative mechanism. Accordingly, we found that Stem Cell Factor (SCF)-activated c-Kit induces phosphorylation of the IL-2Rbeta chain in the absence of IL-2. Moreover, inhibition of IL-2Rbeta phosphorylation by blocking c-Kit tyrosine kinase activity abolishes both, IL-2 and SCF-mediated proliferation. Thus, these results demonstrate that IL-2 triggers a JAK3/STAT5 cascade in HPV-associated cervical cancer cells expressing IL-2Rbetagamma, and that this receptor can be alternatively activated by SCF-activated c-Kit in the absence of IL-2.     

Innate immune recognition of microbes through Nod1 and Nod2: implications for disease

Nod1 and Nod2 are cytosolic proteins involved in intracellular recognition of microbes and their products. Recently, it was shown that these proteins recognize different moieties of bacterial peptidoglycan (PGN) mediating non-specific pathogen resistance and possibly generating signals for the adaptive immune response. Moreover, mutations in the gene encoding Nod2 are associated with increased susceptibility to chronic inflammatory disorders.     

Ethanol formation and enzyme activities around glucose-6-phosphate in Kluyveromyces marxianus CBS 6556 exposed to glucose or lactose excess

The aim of this work was to investigate the physiology of Kluyveromyces marxianus CBS 6556 in terms of its low tendency to form ethanol under exposure to sugar excess, and the split of carbon flux which takes place at the level of glucose-6-phosphate. Measurements were performed in batch cultivations, and after a glucose or a lactose pulse applied to chemostat-grown respiring cells (with a dilution rate of 0.1 h(-1)). No ethanol formation was observed in batch cultivations or during pulse experiments, unless the oxygen supply was shut down, indicating that this organism is more strictly Crabtree-negative than its close relative K. lactis and other known Crabtree-negative yeasts. During the pulse experiments, activities of phosphoglucoisomerase, glucose-6-phosphate dehydrogenase and phosphoglucomutase in cell-free extracts remained rather constant, at higher levels than those of Saccharomyces cerevisiae grown at similar conditions. When cells were exposed to glucose concentrations as high as 26 gl(-1), the activity of phosphoglucomutase was higher than that in cells exposed to 14 gl(-1) glucose, whereas the activities of phosphoglucoisomerase and glucose-6-phosphate dehydrogenase did not change. Our results suggest that the low tendency for ethanol formation in K. marxianus might be a consequence of this yeast's capacity of keeping the glycolytic flux constant, due at least in part to the diversion of carbon flux towards the biosynthesis of carbohydrates and towards the pentose phosphate pathway.     

S-allylmercaptocysteine scavenges hydroxyl radical and singlet oxygen <Emphasis Type="Italic">in vitro</Emphasis> and attenuates gentamicin-induced oxidative and nitrosative stress and renal damage <Emphasis Type="Italic">in vivo</Emphasis>

Background  

Oxidative and nitrosative stress have been involved in gentamicin-induced nephrotoxicity. The purpose of this work was to study the effect of S-allylmercaptocysteine, a garlic derived compound, on gentamicin-induced oxidative and nitrosative stress and nephrotoxicity. In addition, the in vitro reactive oxygen species scavenging properties of S-allylmercaptocysteine were studied.     

Ketogenic Diet Increases Glutathione Peroxidase Activity in Rat Hippocampus

Ketogenic diets have been used in the treatment of refractory childhood epilepsy for almost 80 years; however, we know little about the underlying biochemical basis of their action. In this study, we evaluate oxidative stress in different brain regions from Wistar rats fed a ketogenic diet. Cerebral cortex appears to have not been affected by this diet, and cerebellum presented a decrease in antioxidant capacity measured by a luminol oxidation assay without changes in antioxidant enzyme activities—glutathione peroxidase, catalase, and superoxide dismutase. In the hippocampus, however, we observed an increase in antioxidant activity accompanied by an increase of glutathione peroxidase (about 4 times) and no changes in lipoperoxidation levels. We suggest that the higher activity of this enzyme induced by ketogenic diet in hippocampus might contribute to protect this structure from neurodegenerative sequelae of convulsive disorders.