Screening of Bacterial Isolates from Polluted Soils Exhibiting Catalase and Peroxidase Activity and Diversity of their Responses to Oxidative Stress

For the survival of individual isolates of gram-negative bacteria Pseudomonas putida, Achromobacter xylosoxidans, and the gram-positive bacterium Bacillus megaterium, in an environment polluted with crude oil products, the production of catalases exhibiting both catalase and dianisidine-peroxidase activity is important. Electrophoretic resolution of cell-free extracts of aerobically grown strains in Luria–Bertani medium during exponential phase revealed distinctive expression of catalatic and peroxidatic activities detected with 3,3′-diaminobenzidine tetrahydrochloride. A considerable diversity in microbial catalase and peroxidase responses to 20 or 40 mM H₂O₂ stress, resulted from hydroperoxidase’s variant of original isolates, indicating an environmental selective pressure. However, catalase was important for the adaptation of cultures to high concentration of 60 mM H₂O₂. Appreciable differences in the sensitivity to toxic effect of H₂O₂ (20 or 40 mM) treatment between individual isolates and their adapted variants during growth were observed until the middle of exponential phase, but they were insignificant at the entry to stationary phase. Isolates also exhibited a considerable diversity in catalases responses to phenolic contaminants 1 and 2 mM o- or p-phenylenediamine. Catalase activity of bacterium P. putida was visibly stimulated only by p-phenylenediamine and not by its positional isomer o-PDA. This study contributes to a better understanding of the role catalases play in bacterial responses to a polluted environment.     

An Inhibitor of Tryptophan-Dependent Biosynthesis of Indole-3-Acetic Acid Alters Seedling Development in Arabidopsis

Although polar transport and the TIR1-dependent signaling pathway of the plant hormone auxin/indole-3-acetic acid (IAA) are well characterized, understanding of the biosynthetic pathway(s) leading to the production of IAA is still limited. Genetic dissection of IAA biosynthetic pathways has been complicated by the metabolic redundancy caused by the apparent existence of several parallel biosynthetic routes leading to IAA production. Valuable complementary tools for genetic as well as biochemical analysis of auxin biosynthesis would be molecular inhibitors capable of acting in vivo on specific or general components of the pathway(s), which unfortunately have been lacking. Several indole derivatives have been previously identified to inhibit tryptophan-dependent IAA biosynthesis in an in vitro system from maize endosperm. We examined the effect of one of them, 6-fluoroindole, on seedling development of Arabidopsis thaliana and tested its ability to inhibit IAA biosynthesis in feeding experiments in vivo. We demonstrated a correlation of severe developmental defects or growth retardation caused by 6-fluoroindole with significant downregulation of de novo synthesized IAA levels, derived from the stable isotope-labeled tryptophan pool, upon treatment. Hence, 6-fluoroindole shows important features of an inhibitor of tryptophan-dependent IAA biosynthesis both in vitro and in vivo and thus may find use as a promising molecular tool for the identification of novel components of the auxin biosynthetic pathway(s).     

Changes in abundance of hibernating bats in central Slovakia (1992–2009)

An analysis of long-term changes in abundance of hibernating bats as revealed from the annual monitoring programme conducted in four mountain regions of the Western Carpathians (Muránska planina Mts, Revúcka vrchovina Mts, Slovensky kras Mts, Štiavnické vrchy Mts) during the period 1992–2009 is providing in the paper. Data from 52 hibernacula were analysed. Among 18 bat species recorded, an apparent population increase of three most abundant thermophilous and originally cave dwelling species of bats, Rhinolophus hipposideros, R. ferrumequinum, Myotis myotis, was observed. In other bat species (e.g., R. euryale, M. emarginatus, M. mystacinus, M. dasycneme, Barbastella barbastellus), population trends could not be detected and because of data scarcity, they should be evaluated from more extensive datasets obtained from a wide range of hibernacula or from a completely different type of evidence.     

The kinetics of YOYO-1 intercalation into single molecules of double-stranded DNA

Recent studies have suggested that treatment of glucocorticoid to immature growth hormone (GH)-producing cell line, MtT/S cells, dramatically induced the accumulation of GH-containing secretory granules in the cytosol and differentiated into mature GH-producing cells. However, the molecular mechanism of glucocorticoid-induced GH-containing secretory granule biogenesis in the MtT/S cells remains unknown. In the present study, we found that GH mRNA expression was facilitated by application of glucocorticoid. We artificially increased GH synthesis by transfection of green fluorescent protein-tagged GH (GH-GFP) gene. We found that the artificial elevation of GH expression in the cells did not accumulate the secretory granules in the cytosol, whereas glucocorticoid-induced the biogenesis of granules in GH-GFP-expressing MtT/S cells. We next performed DNA microarray and real-time RT-PCR analysis and found that glucocorticoid significantly altered the expression of membrane trafficking-related protein, syntaxin11 (Syx11). Immunocytochemical analysis further demonstrated that Syx11 positive structures were well colocalized with GH-containing granules in both MtT/S cells and rat anterior pituitary gland. Our findings indicate that glucocorticoid regulate the expression of Syx11 and facilitate the biogenesis and the trafficking of GH-containing granules in the MtT/S cells.     

Ionic partition and transport in multi-ionic channels: a molecular dynamics simulation study of the OmpF bacterial porin

We performed all-atom molecular dynamics simulations studying the partition of ions and the ionic current through the bacterial porin OmpF and two selected mutants. The study is motivated by new, interesting experimental findings concerning their selectivity and conductance behavior at neutral pH. The mutations considered here are designed to study the effect of removal of negative charges present in the constriction zone of the wild-type OmpF channel (which contains, on one side, a cluster with three positive residues, and on the other side, two negatively charged residues). Our results show that these mutations induce an exclusion of cations from the constriction zone of the channel, substantially reducing the flow of cations. In fact, the partition of ions inside the mutant channels is strongly inhomogeneous, with regions containing an excess of cations and regions containing an excess of anions. Interestingly, the overall number of cations inside the channel is larger than the number of anions, this excess being different for each protein channel. We found that the differences in ionic charge inside these channels are justified by the differences in electric charge between the wild-type OmpF and the mutants, following an electroneutral balance.     

Insights from the eco‐physiological book of records: Bewick's swans outperform the canonical intake‐maximizing vertebrate

During periods of high energy demand an animal may be constrained by a physiological maximum to its energy intake rate. Predictions by allometric equations describing this maximum for endotherms were significantly surpassed during a few recent laboratory experiments on birds and mammals, being given access to food 24 h day^?1. How relevant this is in the field remains to be assessed. We predicted that Bewick's swans Cygnus columbianus bewickii might surpass this maximum during stopover on their migration. We determined intake rate by measuring initial and final biomass density, and dividing the biomass difference by the feeding time required to reach this difference. This feeding time was given by the functional response. After conversion to daily energy intake rates, these exceeded the previously assumed maximum on two of the three stopover sites studied. The exception was a stopover site where daily foraging time was limited by the tidal cycle. Our study confirms that intake rates may exceed the formerly generally supposed maximum under natural conditions when foraging is possible day and night.     

Temporal differences in food abundance promote coexistence between two congeneric passerines

Many related species share the same environment and utilize similar resources. This is surprising because based on the principle of competitive exclusion one would predict that the superior competitor would drive the other species to extinction; coexistence is only predicted if interspecific competition is weaker than intraspecific competition. Interspecific competition is frequently reduced by differential resource use, resulting in habitat segregation. In this paper, we use the closely related collared and pied flycatcher to assess the potential of habitat differences to affect interspecific competition through a different mechanism, namely by generating temporal differences in availability of similar food resources between the two species. We found that the tree species composition of the breeding territories of the two species differed, mainly by a higher abundance of coniferous species around nest-boxes occupied by pied flycatchers. The temporal availability of caterpillars was measured using frass traps under four deciduous and two coniferous tree species. Deciduous tree species showed an early and narrow peak in abundance, which contrasted with the steady increase in caterpillar abundance in the coniferous tree species through the season. We subsequently calculated the predicted total caterpillar biomass available in each flycatcher territory. This differed between the species, with biomass decreasing more slowly in pied flycatcher territories. Caterpillar biomass is strongly correlated with the reproductive success of collared flycatchers, but much less so with pied flycatchers. However, caterpillar availability can only partly explain the differences in seasonal decline of reproductive success between the two species; we discuss additional factors that may contribute to this species difference. Overall, our results are consistent with the suggestion that minor habitat differences between these two species may contribute to promoting their coexistence.     

Inhibition of C6 rat glioma proliferation by [Ru2Cl(Ibp)4] depends on changes in p21, p27, Bax/Bcl2 ratio and mitochondrial membrane potential

The ruthenium compound [Ru₂Cl(Ibp)₄] (or RuIbp) has been reported to cause significantly greater inhibition of C6 glioma cell proliferation than the parent HIbp. The present study determined the effects of 0-72 h exposure to RuIbp upon C6 cell cycle distribution, mitochondrial membrane potential, reactive species generation and mRNA and protein expression of E2F1, cyclin D1, c-myc, pRb, p21, p27, p53, Ku70, Ku80, Bax, Bcl2, cyclooxygenase 1 and 2 (COX1 and COX2). The most significant changes in mRNA and protein expression were seen for the cyclin-dependent kinase inhibitors p21 and p27 which were both increased (p < 0.05). The marked decrease in mitochondrial membrane potential (p < 0.01) and modest increase in apoptosis was accompanied by a decrease in anti-apoptotic Bcl2 expression and an increase in pro-apoptotic Bax expression (p < 0.05). Interestingly, COX1 expression was increased in response to a significant loss of prostaglandin E₂ production (p < 0.001), most likely due to the intracellular action of Ibp. Future studies will investigate the efficacy of this novel ruthenium-ibuprofen complex in human glioma cell lines in vitro and both rat and human glioma cells growing under orthotopic conditions in vivo.