Na-G-penicillin penetration into rat cerebral cortex and formation of an epileptic focus.

Fluorescein isothiocyanate-labelled Na-G-penicillin was applied to the intact dura of 11 rats and the cortical layers were determined to which this epileptogenic substance must penetrate for electrophysiologically demonstrable focal activity to be induced. In 10 animals labelled penicillin was demonstrated in cortical layers I--III and in one animal in layers I and II. This concurs with the results obtained in 12 other animals in which activity was recorded from three depths of the cerebral cortex with semimicroelectrodes.     

Neovahlkampfia nana n. sp. Reinforcing an Underrepresented Subclade of Tetramitia,Heterolobosea

The study provides robust genetic evidence that a newly isolated naked ameba with morphological and ultrastructural features indicative of Heterolobosea is a new species. Neovahlkampfia nana n. sp. associates with the yet underrepresented subclade of Tetramitia I. Considerable differences found in 18S rRNA gene sequences of individual molecular clones derived from DNA of five clonal cultures, using a low fidelity DNA polymerase, raised the issue of intragenomic sequence variation, a phenomenon that has not been previously studied in Heterolobosea. However, as proved using a higher fidelity DNA polymerase, the sequence variability observed was introduced by PCR mediated by the low fidelity polymerase and fixed by molecular cloning. This points to the potentially dubious validity of some current nominal species of Heterolobosea that differ from one another in just one or two base positions.     

Biological invasions in forest ecosystems: a global problem requiring international and multidisciplinary integration

The world’s forests are crucial biological resources that provide a variety of ecosystem services such as nutrient cycling and provisioning of resources to society. But forests are particularly affected by biological invasions, with regions around the world experiencing invasions by species from virtually every kingdom. Many of these species have severely disrupted forest ecosystem processes, thereby interrupting the provisioning of ecosystem services that societies depend upon. The problem of biological invasion in forests has many facets, and a large diversity of scientific disciplines addresses these issues. To make progress in solving the problems forest invasions pose, developing interdisciplinary collaborations is crucial because the causes of invasions and many of the measures for prevention or management require expertise in biology, economics, and social sciences. The goal of this special issue is to compile a series of articles summarizing various biological, sociological, and policy subject areas associated with forest invasions from a global perspective. These papers were prepared by the task force, “Forests and Biological Invasions,” organized by the International Union of Forest Research Organizations. Publication of this special issue is intended to advance the integration of scientific knowledge and development of solutions to this very serious and growing problem.     

Non-native plantation forests as alternative habitat for native forest beetles in a heavily modified landscape

The once extensive native forests of New Zealand’s central North Island are heavily fragmented, and the scattered remnants are now surrounded by a matrix of exotic pastoral grasslands and Pinus radiata plantation forests. The importance of these exotic habitats for native biodiversity is poorly understood. This study examines the utilisation of exotic plantation forests by native beetles in a heavily modified landscape. The diversity of selected beetle taxa was compared at multiple distances across edge gradients between each of the six possible combinations of adjacent pastoral, plantation, clearfell and native forest land-use types. Estimated species richness (Michaelis–Menten) was greater in production habitats than native forest; however this was largely due to the absence of exotic species in native forest. Beetle relative abundance was highest in clearfell-harvested areas, mainly due to colonisation by open-habitat, disturbance-adapted species. More importantly, though, of all the non-native habitats sampled, beetle species composition in mature P. radiata was most similar to native forest. Understanding the influence of key environmental factors and stand level management is important for enhancing biodiversity values within the landscape. Native habitat proximity was the most significant environmental correlate of beetle community composition, highlighting the importance of retaining native remnants within plantation landscapes. The proportion of exotic beetles was consistently low in mature plantation stands, however it increased in pasture sites at increasing distances from native forest. These results suggest that exotic plantation forests may provide important alternative habitat for native forest beetles in landscapes with a low proportion of native forest cover.     

Functional diversity and electron donor dependence of microbial populations capable of U(VI) reduction in radionuclide-contaminated subsurface sediments

In order to elucidate the potential mechanisms of U(VI) reduction for the optimization of bioremediation strategies, the structure-function relationships of microbial communities were investigated in microcosms of subsurface materials cocontaminated with radionuclides and nitrate. A polyphasic approach was used to assess the functional diversity of microbial populations likely to catalyze electron flow under conditions proposed for in situ uranium bioremediation. The addition of ethanol and glucose as supplemental electron donors stimulated microbial nitrate and Fe(III) reduction as the predominant terminal electron-accepting processes (TEAPs). U(VI), Fe(III), and sulfate reduction overlapped in the glucose treatment, whereas U(VI) reduction was concurrent with sulfate reduction but preceded Fe(III) reduction in the ethanol treatments. Phyllosilicate clays were shown to be the major source of Fe(III) for microbial respiration by using variable-temperature Mössbauer spectroscopy. Nitrate- and Fe(III)-reducing bacteria (FeRB) were abundant throughout the shifts in TEAPs observed in biostimulated microcosms and were affiliated with the genera Geobacter, Tolumonas, Clostridium, Arthrobacter, Dechloromonas, and Pseudomonas. Up to two orders of magnitude higher counts of FeRB and enhanced U(VI) removal were observed in ethanol-amended treatments compared to the results in glucose-amended treatments. Quantification of citrate synthase (gltA) levels demonstrated a stimulation of Geobacteraceae activity during metal reduction in carbon-amended microcosms, with the highest expression observed in the glucose treatment. Phylogenetic analysis indicated that the active FeRB share high sequence identity with Geobacteraceae members cultivated from contaminated subsurface environments. Our results show that the functional diversity of populations capable of U(VI) reduction is dependent upon the choice of electron donor.Uranium contamination in subsurface environments is a widespread problem at mining and milling sites across North America, South America, and Eastern Europe (1). Uranium in the oxidized state, U(VI), is highly soluble and toxic and thus is a potential contaminant to local drinking-water supplies (46). Nitrate is often a cocontaminant with U(VI) as a result of the use of nitric acid in the processing of uranium and uranium-bearing waste (6, 45). Oxidized uranium can be immobilized in contaminated groundwater through the reduction of U(VI) to insoluble U(IV) by indirect (abiotic) and direct (enzymatic) processes catalyzed by microorganisms. Current remediation practices favor the stimulation of reductive uranium immobilization catalyzed by indigenous microbial communities along with natural attenuation and monitoring (5, 24, 40, 44, 65, 68, 69). Microbial uranium reduction activity in contaminated subsurface environments is often limited by carbon or electron donor availability (13, 24, 44, 69). Previous studies have indicated that U(VI) reduction does not proceed until nitrate is depleted (13, 16, 24, 44, 68, 69), as high nitrate concentrations inhibit the reduction of U(VI) by serving as a competing and more energetically favorable terminal electron acceptor for microorganisms (11, 16). The fate and transport of uranium in groundwater are also strongly linked through sorption and precipitation processes to the bioreduction of Fe minerals, including oxides, layer-silicate clay minerals, and sulfides (7, 23, 53).In order to appropriately design U(VI) bioremediation strategies, the potential function and phylogenetic structure of indigenous subsurface microbial communities must be further understood (24, 34, 46). Conflicting evidence has been presented on which microbial groups, Fe(III)- or sulfate-reducing bacteria (FeRB or SRB), effectively catalyze the reductive immobilization of U(VI) in the presence of amended electron donors (5, 44, 69). The addition of acetate to the subsurface at a uranium-contaminated site in Rifle, Colorado, initially stimulated FeRB within the family Geobacteraceae to reduce U(VI) (5, 65). However, with long-term acetate addition, SRB within the family Desulfobacteraceae, which are not capable of U(VI) reduction, increased in abundance and a concomitant reoxidation of U(IV) was observed (5, 65). At a uranium-contaminated site in Oak Ridge, Tennessee, in situ and laboratory-based experiments successfully employed ethanol amendments to stimulate denitrification followed by the reduction of U(VI) by indigenous microbial communities (13, 24, 44, 48, 50, 57, 68). In these studies, ethanol amendments stimulated both SRB and FeRB, with SRB likely catalyzing the reduction of U(VI). This suggests that the potential for bioremediation will be affected by the choice of electron donor amendment through effects on the functional diversity of U(VI)-reducing microbial populations. As uranium reduction is dependent on the depletion of nitrate, the microbial populations mediating nitrate reduction are also critical to the design of bioremediation strategies. Although nitrate-reducing bacteria (NRB) have been studied extensively in subsurface environments (2, 15, 19, 24, 56, 58, 70), the mechanisms controlling the in situ metabolism of NRB remain poorly understood.The dynamics of microbial populations capable of U(VI) reduction in subsurface sediments are poorly understood, and the differences in the microbial community dynamics during bioremediation have not been explored. Based on the results of previous studies (13, 44, 49, 57, 68, 69), we hypothesized that the activity of nitrate- and Fe(III)-reducing microbial populations, catalyzing the reductive immobilization of U(VI) in subsurface radionuclide-contaminated sediments, would be dependent on the choice of electron donor. The objectives of the present study were (i) to characterize structure-function relationships for microbial groups likely to catalyze or limit U(VI) reduction in radionuclide-contaminated sediments and (ii) to further develop a proxy for the metabolic activity of FeRB. Microbial activity was assessed by monitoring terminal electron-accepting processes (TEAPs), electron donor utilization, and Fe(III) mineral transformations in microcosms conducted with subsurface materials cocontaminated with high levels of U(VI) and nitrate. In parallel, microbial functional groups (i.e., NRB and FeRB) were enumerated and characterized using a combination of cultivation-dependent and -independent methods.     

Importin 13: a novel mediator of nuclear import and export.

Importin beta-related receptors mediate translocation through nuclear pore complexes. Co-operation with the RanGTPase system allows them to bind and subsequently release their substrates on opposite sides of the nuclear envelope, which in turn ensures a directed nucleocytoplasmic transport. Here we identify a novel family member from higher eukaryotes that functions primarily, but not exclusively, in import. It accounts for nuclear accumulation of the SUMO-1/sentrin-conjugating enzyme hUBC9 and mediates import of the RBM8 (Y14) protein, and is therefore referred to as importin 13 (Imp13). Unexpectedly, Imp13 also shows export activity towards the translation initiation factor eIF1A and is thus a case where a single importin beta-like receptor transports different substrates in opposite directions. However, Imp13 operates differently from typical exportins in that the binding of eIF1A to Imp13 is only regulated indirectly by RanGTP, and the cytoplasmic release of eIF1A from Imp13 is triggered by the loading of import substrates onto Imp13.