Showing papers by "University of Guelph published in 2006"
TL;DR: In this article, a review of adaptation of human communities to global changes, especially climate change, in the context of adaptive capacity and vulnerability is presented, focusing on scholarship that contributes to practical implementation of adaptations at the community scale.
Abstract: This paper reviews the concept of adaptation of human communities to global changes, especially climate change, in the context of adaptive capacity and vulnerability. It focuses on scholarship that contributes to practical implementation of adaptations at the community scale. In numerous social science fields, adaptations are considered as responses to risks associated with the interaction of environmental hazards and human vulnerability or adaptive capacity. In the climate change field, adaptation analyses have been undertaken for several distinct purposes. Impact assessments assume adaptations to estimate damages to longer term climate scenarios with and without adjustments. Evaluations of specified adaptation options aim to identify preferred measures. Vulnerability indices seek to provide relative vulnerability scores for countries, regions or communities. The main purpose of participatory vulnerability assessments is to identify adaptation strategies that are feasible and practical in communities. The distinctive features of adaptation analyses with this purpose are outlined, and common elements of this approach are described. Practical adaptation initiatives tend to focus on risks that are already problematic, climate is considered together with other environmental and social stresses, and adaptations are mostly integrated or mainstreamed into other resource management, disaster preparedness and sustainable development programs. r 2006 Elsevier Ltd. All rights reserved.
4,612 citations
TL;DR: Nanowires produced by the oxygenic phototrophic cyanobacterium Synechocystis PCC6803 and the thermophilic, fermentative bacterium Pelotomaculum thermopropionicum reveal that electrically conductive appendages are not exclusive to dissimilatory metal-reducing bacteria and may, in fact, represent a common bacterial strategy for efficient electron transfer and energy distribution.
Abstract: Shewanella oneidensis MR-1 produced electrically conductive pilus-like appendages called bacterial nanowires in direct response to electron-acceptor limitation. Mutants deficient in genes for c-type decaheme cytochromes MtrC and OmcA, and those that lacked a functional Type II secretion pathway displayed nanowires that were poorly conductive. These mutants were also deficient in their ability to reduce hydrous ferric oxide and in their ability to generate current in a microbial fuel cell. Nanowires produced by the oxygenic phototrophic cyanobacterium Synechocystis PCC6803 and the thermophilic, fermentative bacterium Pelotomaculum thermopropionicum reveal that electrically conductive appendages are not exclusive to dissimilatory metal-reducing bacteria and may, in fact, represent a common bacterial strategy for efficient electron transfer and energy distribution.
1,666 citations
TL;DR: It is shown that cytochrome c oxidase I DNA barcodes effectively discriminate among species in three Lepidoptera families from Area de Conservación Guanacaste in northwestern Costa Rica, suggesting DNA barcoding will significantly aid species identification and discovery in tropical settings.
Abstract: Although central to much biological research, the identification of species is often difficult. The use of DNA barcodes, short DNA sequences from a standardized region of the genome, has recently been proposed as a tool to facilitate species identification and discovery. However, the effectiveness of DNA barcoding for identifying specimens in species-rich tropical biotas is unknown. Here we show that cytochrome c oxidase I DNA barcodes effectively discriminate among species in three Lepidoptera families from Area de Conservacion Guanacaste in northwestern Costa Rica. We found that 97.9% of the 521 species recognized by prior taxonomic work possess distinctive cytochrome c oxidase I barcodes and that the few instances of interspecific sequence overlap involve very similar species. We also found two or more barcode clusters within each of 13 supposedly single species. Covariation between these clusters and morphological and/or ecological traits indicates overlooked species complexes. If these results are general, DNA barcoding will significantly aid species identification and discovery in tropical settings.
1,288 citations
TL;DR: This study presents a silica-based method that is sensitive, inexpensive and compliant with automation that has now been tested on more than 5000 animal specimens with highly positive results.
Abstract: Although commercial kits are available for automated DNA extraction, ‘artisanal’ protocols are not. In this study, we present a silica-based method that is sensitive, inexpensive and compliant with automation. The effectiveness of this protocol has now been tested on more than 5000 animal specimens with highly positive results.
1,233 citations
TL;DR: The pattern of contamination in wildlife varied among species and locations suggesting multiple emission sources and knowledge gaps with respect to the transport, accumulation, biodegradation, temporal/spatial trends and PFS precursors have been identified.
Abstract: Polyfluoroalkyl substances (PFSs) are used in industrial and commercial products and can degrade to persistent perfluorocarboxylates (PFCAs) and perfluoroalkyl sulfonates (PFSAs). Temporal trend st...
1,139 citations
TL;DR: In gram-negative bacteria, it is proposed that biosynthesis and translocation of capsular polysaccharides to the cell surface are temporally and spatially coupled by multiprotein complexes that span the cell envelope.
Abstract: Capsules are protective structures on the surfaces of many bacteria. The remarkable structural diversity in capsular polysaccharides is illustrated by almost 80 capsular serotypes in Escherichia coli. Despite this variation, the range of strategies used for capsule biosynthesis and assembly is limited, and E. coli isolates provide critical prototypes for other bacterial species. Related pathways are also used for synthesis and export of other bacterial glycoconjugates and some enzymes/processes have counterparts in eukaryotes. In gram-negative bacteria, it is proposed that biosynthesis and translocation of capsular polysaccharides to the cell surface are temporally and spatially coupled by multiprotein complexes that span the cell envelope. These systems have an impact on both a general understanding of membrane trafficking in bacteria and on bacterial pathogenesis.
946 citations
TL;DR: In this paper, the authors developed indicators to measure community tourism development within a sustainable framework using a modified Delphi technique, which employed a panel of 38 academic researchers in tourism provided input into developing the indicators.
921 citations
TL;DR: Genome-wide selection may become a popular tool for genetic improvement in livestock after a strategy that utilizes these advantages was compared with a traditional progeny testing strategy under a typical Canadian-like dairy cattle situation.
Abstract: Animals can be genotyped for thousands of single nucleotide polymorphisms (SNPs) at one time, where the SNPs are located at roughly 1-cM intervals throughout the genome. For each contiguous pair of SNPs there are four possible haplotypes that could be inherited from the sire. The effects of each interval on a trait can be estimated for all intervals simultaneously in a model where interval effects are random factors. Given the estimated effects of each haplotype for every interval in the genome, and given an animal's genotype, a 'genomic' estimated breeding value is obtained by summing the estimated effects for that genotype. The accuracy of that estimator of breeding values is around 80%. Because the genomic estimated breeding values can be calculated at birth, and because it has a high accuracy, a strategy that utilizes these advantages was compared with a traditional progeny testing strategy under a typical Canadian-like dairy cattle situation. Costs of proving bulls were reduced by 92% and genetic change was increased by a factor of 2. Genome-wide selection may become a popular tool for genetic improvement in livestock.
785 citations
TL;DR: Novel evidence is presented that antifungal phytochemistry of the invasive plant, Alliaria petiolata, a European invader of North American forests, suppresses native plant growth by disrupting mutualistic associations between native canopy tree seedlings and belowground arbuscular mycorrhizal fungi.
Abstract: The impact of exotic species on native organisms is widely acknowledged, but poorly understood. Very few studies have empirically investigated how invading plants may alter delicate ecological interactions among resident species in the invaded range. We present novel evidence that antifungal phytochemistry of the invasive plant, Alliaria petiolata, a European invader of North American forests, suppresses native plant growth by disrupting mutualistic associations between native canopy tree seedlings and belowground arbuscular mycorrhizal fungi. Our results elucidate an indirect mechanism by which invasive plants can impact native flora, and may help explain how this plant successfully invades relatively undisturbed forest habitat.
775 citations
TL;DR: It is concluded that species introductions generally alter plants' interactions with enemies, mutualists and competitors, and that there is increasing evidence that these altered interactions jointly influence the success of introduced populations.
Abstract: Introduced plant populations lose interactions with enemies, mutualists and competitors from their native ranges, and gain interactions with new species, under new abiotic conditions. From a biogeographical perspective, differences in the assemblage of interacting species, as well as in abiotic conditions, may explain the demographic success of the introduced plant populations relative to conspecifics in their native range. Within invaded communities, the new interactions and conditions experienced by the invader may influence both its demographic success and its effects on native biodiversity. Here, we examine indirect effects involving enemies, mutualists and competitors of introduced plants, and effects of abiotic conditions on biotic interactions. We then synthesize ideas building on Darwin’s idea that the kinds of new interactions gained by an introduced population will depend on its relatedness to native populations. This yields a heuristic framework to explain how biotic interactions and abiotic conditions influence invader success. We conclude that species introductions generally alter plants interactions with enemies, mutualists and competitors, and that there is increasing evidence that these altered interactions jointly influence the success of introduced populations. Ecology Letters (2006) 9: 726‐740
761 citations
TL;DR: In this paper, the authors show that real food webs are structured such that top predators act as couplers of distinct energy channels that differ in both productivity and turnover rate, and that coupled fast and slow channels convey both local and non-local stability to food webs.
Abstract: Untangling the influence of human activities on food-web stability and persistence is complex given the large numbers of species and overwhelming number of interactions within ecosystems. Although biodiversity has been associated with stability, the actual structures and processes that confer stability to diverse food webs remain largely unknown. Here we show that real food webs are structured such that top predators act as couplers of distinct energy channels that differ in both productivity and turnover rate. Our theoretical analysis shows that coupled fast and slow channels convey both local and non-local stability to food webs. Alarmingly, the same human actions that have been implicated in the loss of biodiversity also directly erode the very structures and processes that we show to confer stability on food webs.
TL;DR: The main models of innovation diffusion were established by 1970 as discussed by the authors, and the main categories of these modifications are: the introduction of marketing variables in the parameterisation of the models; generalising the models to consider innovations at different stages of diffusions in different countries; and generalizing the models by considering the diffusion of successive generations of technology.
TL;DR: In this paper, a conceptual model to investigate population migration as a possible adaptive response to risks associated with climate change is presented, based upon the concepts of vulnerability, exposure to risk and adaptive capacity, as developed in the climate change research community.
Abstract: This article presents a conceptual model to investigate population migration as a possible adaptive response to risks associated with climate change. The model reflects established theories of human migration behaviour, and is based upon the concepts of vulnerability, exposure to risk and adaptive capacity, as developed in the climate change research community. The application of the model is illustrated using the case of 1930s migration patterns in rural Eastern Oklahoma, which took place during a period of repeated crop failures due to drought and flooding.
TL;DR: If general, these results will increase estimates of global species richness and imply that tropical conservation and host-parasite interactions may be more complex than expected.
Abstract: Insect parasitoids are a major component of global biodiversity and affect the population dynamics of their hosts. However, identification of insect parasitoids is often difficult, and they are suspected to contain many cryptic species. Here, we ask whether the cytochrome c oxidase I DNA barcode could function as a tool for species identification and discovery for the 20 morphospecies of Belvosia parasitoid flies (Diptera: Tachinidae) that have been reared from caterpillars (Lepidoptera) in Area de Conservacion Guanacaste (ACG), northwestern Costa Rica. Barcoding not only discriminates among all 17 highly host-specific morphospecies of ACG Belvosia, but it also raises the species count to 32 by revealing that each of the three generalist species are actually arrays of highly host-specific cryptic species. We also identified likely hybridization among Belvosia by using a variable internal transcribed spacer region 1 nuclear rDNA sequence as a genetic covariate in addition to the strategy of overlaying barcode clusters with ecological information. If general, these results will increase estimates of global species richness and imply that tropical conservation and host–parasite interactions may be more complex than expected.
TL;DR: It is suggested that DGAT1 and DGAT2 have nonredundant functions in plants and that the production of storage oils, including those containing unusual fatty acids, occurs in distinct ER subdomains.
Abstract: Seeds of the tung tree (Vernicia fordii) produce large quantities of triacylglycerols (TAGs) containing ∼80% eleostearic acid, an unusual conjugated fatty acid. We present a comparative analysis of the genetic, functional, and cellular properties of tung type 1 and type 2 diacylglycerol acyltransferases (DGAT1 and DGAT2), two unrelated enzymes that catalyze the committed step in TAG biosynthesis. We show that both enzymes are encoded by single genes and that DGAT1 is expressed at similar levels in various organs, whereas DGAT2 is strongly induced in developing seeds at the onset of oil biosynthesis. Expression of DGAT1 and DGAT2 in yeast produced different types and proportions of TAGs containing eleostearic acid, with DGAT2 possessing an enhanced propensity for the synthesis of trieleostearin, the main component of tung oil. Both DGAT1 and DGAT2 are located in distinct, dynamic regions of the endoplasmic reticulum (ER), and surprisingly, these regions do not overlap. Furthermore, although both DGAT1 and DGAT2 contain a similar C-terminal pentapeptide ER retrieval motif, this motif alone is not sufficient for their localization to specific regions of the ER. These data suggest that DGAT1 and DGAT2 have nonredundant functions in plants and that the production of storage oils, including those containing unusual fatty acids, occurs in distinct ER subdomains.
TL;DR: Short barcodes were effective in identifying specimens, confirming their utility in circumstances where full barcodes are too expensive to obtain and the identification comparisons are within a confined taxonomic group.
Abstract: A DNA barcode based on 650 bp of mitochondrial gene cytochrome c oxidase I is proving to be highly functional in species identification for various animal groups. However, DNA degradation complicates the recovery of a full-length barcode from many museum specimens. Here we explore the use of shorter barcode sequences for identification of such specimens. We recovered short sequences — i.e. ∼ 100 bp — with a single PCR pass from more than 90% of the specimens in assemblages of moth and wasp museum specimens from which full barcode recovery was only 50%, and the latter were usually less than 8 years old. Short barcodes were effective in identifying specimens, confirming their utility in circumstances where full barcodes are too expensive to obtain and the identification comparisons are within a confined taxonomic group.
TL;DR: It is shown that membrane vesicles (MVs), structures derived from the outer membrane of gram-negative bacteria, are a common particulate feature of the matrix of Pseudomonas aeruginosa biofilms and were established as common biofilm constituents.
Abstract: The matrix helps define the architecture and infrastructure of biofilms and also contributes to their resilient nature. Although many studies continue to define the properties of both gram-positive and gram-negative bacterial biofilms, there is still much to learn, especially about how structural characteristics help bridge the gap between the chemistry and physical aspects of the matrix. Here, we show that membrane vesicles (MVs), structures derived from the outer membrane of gram-negative bacteria, are a common particulate feature of the matrix of Pseudomonas aeruginosa biofilms. Biofilms grown using different model systems and growth conditions were shown to contain MVs when thin sectioned for transmission electron microscopy, and mechanically disrupted biofilms revealed MVs in association with intercellular material. MVs were also isolated from biofilms by employing techniques for matrix isolation and a modified MV isolation protocol. Together these observations verified the presence and frequency of MVs and indicated that MVs were a definite component of the matrix. Characterization of planktonic and biofilm-derived MVs revealed quantitative and qualitative differences between the two and indicated functional roles, such as proteolytic activity and binding of antibiotics. The ubiquity of MVs was supported by observations of biofilms from a variety of natural environments outside the laboratory and established MVs as common biofilm constituents. MVs appear to be important and relatively unacknowledged particulate components of the matrix of gram-negative or mixed bacterial biofilms.
Centers for Disease Control and Prevention1, International Maize and Wheat Improvement Center2, Indian Council of Medical Research3, World Health Organization4, Johns Hopkins University5, International Institute of Tropical Agriculture6, Center for Food Safety and Applied Nutrition7, Agricultural & Applied Economics Association8, University of Alabama at Birmingham9, Chinese Center for Disease Control and Prevention10, Istituto Superiore di Sanità11, National University of Singapore12, United States Department of Agriculture13, Center for Food Safety14, Food and Agriculture Organization15, Instituto Adolfo Lutz16, University of Guelph17, South African Medical Research Council18, University of Leeds19, University of Georgia20
TL;DR: A workgroup of international experts and health officials convened in Geneva, Switzerland, in July 2005 identified gaps in current knowledge about acute and chronic human health effects of aflatoxins, surveillance and food monitoring, analytic methods, and the efficacy of intervention strategies.
Abstract: Consecutive outbreaks of acute aflatoxicosis in Kenya in 2004 and 2005 caused > 150 deaths. In response, the Centers for Disease Control and Prevention and the World Health Organization convened a workgroup of international experts and health officials in Geneva, Switzerland, in July 2005. After discussions concerning what is known about aflatoxins, the workgroup identified gaps in current knowledge about acute and chronic human health effects of aflatoxins, surveillance and food monitoring, analytic methods, and the efficacy of intervention strategies. The workgroup also identified public health strategies that could be integrated with current agricultural approaches to resolve gaps in current knowledge and ultimately reduce morbidity and mortality associated with the consumption of aflatoxin-contaminated food in the developing world. Four issues that warrant immediate attention were identified: a) quantify the human health impacts and the burden of disease due to aflatoxin exposure; b) compile an inventory, evaluate the efficacy, and disseminate results of ongoing intervention strategies; c) develop and augment the disease surveillance, food monitoring, laboratory, and public health response capacity of affected regions; and d) develop a response protocol that can be used in the event of an outbreak of acute aflatoxicosis. This report expands on the workgroup's discussions concerning aflatoxin in developing countries and summarizes the findings.
TL;DR: The authors developed a vulnerability-based approach to characterize the human implications of climate change in Arctic Bay, Canada, focusing on community vulnerabilities associated with resource harvesting and the processes through which people adapt to them in the context of livelihood assets, constraints, and outside influences.
Abstract: This paper develops a vulnerability-based approach to characterize the human implications of climate change in Arctic Bay, Canada. It focuses on community vulnerabilities associated with resource harvesting and the processes through which people adapt to them in the context of livelihood assets, constraints, and outside influences. Inuit in Arctic Bay have demonstrated significant adaptability in the face of changing climate-related exposures. This adaptability is facilitated by traditional Inuit knowledge, strong social networks, flexibility in seasonal hunting cycles, some modern technologies, and economic support. Changing Inuit livelihoods, however, have undermined certain aspects of adaptive capacity, and have resulted in emerging vulnerabilities in certain sections of the community.
TL;DR: The greatest advances in dairy health in the last 25 yr have been the shifts to disease prevention, rather than treatment, as well as from focus on individual animals to groups and herds, and links between cattle and people through consideration of environmental or ecosystem health.
TL;DR: Data demonstrate the crucial role of early endosomal acidification and V-ATPase/ARNO/Arf6 interactions in the regulation of the endocytic degradative pathway and indicate that V-atPase could modulate membrane trafficking by recruiting and interacting with ARNO and Arf6; characteristics that are consistent with the role of V- ATPase as an essential component of theendosomal pH-sensing machinery.
Abstract: The recruitment of the small GTPase Arf6 and ARNO from cytosol to endosomal membranes is driven by V-ATPase-dependent intra-endosomal acidification. The molecular mechanism that mediates this pH-sensitive recruitment and its role are unknown. Here, we demonstrate that Arf6 interacts with the c-subunit, and ARNO with the a2-isoform of V-ATPase. The a2-isoform is targeted to early endosomes, interacts with ARNO in an intra-endosomal acidification-dependent manner, and disruption of this interaction results in reversible inhibition of endocytosis. Inhibition of endosomal acidification abrogates protein trafficking between early and late endosomal compartments. These data demonstrate the crucial role of early endosomal acidification and V-ATPase/ARNO/Arf6 interactions in the regulation of the endocytic degradative pathway. They also indicate that V-ATPase could modulate membrane trafficking by recruiting and interacting with ARNO and Arf6; characteristics that are consistent with the role of V-ATPase as an essential component of the endosomal pH-sensing machinery.
TL;DR: Different and novel aspects of handoff are presented and handoff related issues of fourth generation systems are discussed and desirable handoff features are presented.
Abstract: As mobile wireless networks increase in popularity and pervasiveness, we are faced with the challenge of combining a diverse number of wireless networks. The fourth generation of wireless communications is expected to integrate a potentially large number of heterogeneous wireless technologies in what could be considered a huge step forward toward universal seamless access. One of the main challenges for seamless mobility is the availability of reliable horizontal (intrasystem) and vertical (intersystem) handoff schemes. Efficient handoff schemes enhance quality of service and provide flawless mobility. This article presents different and novel aspects of handoff and discusses handoff related issues of fourth generation systems. Desirable handoff features are presented. Handoff decisions, radio link transfer, and channel assignment are described as stages of the complete handoff process. A vertical handoff decision function, which enables devices to assign weights to different network parameters, is also presented
TL;DR: The chemical composition of rocks and soils on Mars analyzed during the Mars Exploration Rover Spirit Mission was determined by X-ray analyses with the Alpha Particle X-Ray Spectrometer (APXS) as discussed by the authors.
Abstract: The chemical composition of rocks and soils on Mars analyzed during the Mars Exploration Rover Spirit Mission was determined by X-ray analyses with the Alpha Particle X-Ray Spectrometer (APXS). Details of the data analysis method and the instrument calibration are presented. Measurements performed on Mars to address geometry effects and background contributions are shown. Cross calibration measurements among several instrument sensors and sources are discussed. An unintentional swap of the two flight instruments is evaluated. New concentration data acquired during the first 470 sols of rover Spirit in Gusev Crater are presented. There are two geological regions, the Gusev plains and the Columbia Hills. The plains contain soils that are very similar to previous landing sites on Mars. A meteoritic component in the soil is identified. Rocks in the plains revealed thin weathering rinds. The underlying abraded rock was classified as primitive basalt. One of these rocks contained significant Br that is probably associated with vein-filling material of different composition. One of the trenches showed large subsurface enrichments of Mg, S, and Br. Disturbed soils and rocks in the Columbia Hills revealed different elemental compositions. These rocks are significantly weathered and enriched in mobile elements, such as P, S, Cl, or Br. Even abraded rock surfaces have high Br concentrations. Thus, in contrast to the rocks and soils in the Gusev Plains, the Columbia Hills material shows more significant evidence of ancient aqueous alteration.
TL;DR: The Moessbauer spectrometer on Spirit measured the oxidation state of Fe, identified Fe-bearing phases, and measured relative abundances of Fe among those phases for surface materials on the plains and in the Columbia Hills of Gusev crater as discussed by the authors.
Abstract: The Moessbauer spectrometer on Spirit measured the oxidation state of Fe, identified Fe-bearing phases, and measured relative abundances of Fe among those phases for surface materials on the plains and in the Columbia Hills of Gusev crater. Eight Fe-bearing phases were identified: olivine, pyroxene, ilmenite, magnetite, nanophase ferric oxide (npOx), hematite, goethite, and a Fe(3+)-sulfate. Adirondack basaltic rocks on the plains are nearly unaltered (Fe(3+)/Fe(sub T) Px), and minor npOx and magnetite. Columbia Hills basaltic rocks are nearly unaltered (Peace and Backstay), moderately altered (WoolyPatch, Wishstone, and Keystone), and pervasively altered (e.g., Clovis, Uchben, Watchtower, Keel, and Paros with Fe(3+)/Fe(sub T) approx.0.6-0.9). Fe from pyroxene is greater than Fe from olivine (Ol sometimes absent), and Fe(2+) from Ol+Px is 40-49% and 9-24% for moderately and pervasively altered materials, respectively. Ilmenite (Fe from Ilm approx.3-6%) is present in Backstay, Wishstone, Keystone, and related rocks along with magnetite (Fe from Mt approx. 10-15%). Remaining Fe is present as npOx, hematite, and goethite in variable proportions. Clovis has the highest goethite content (Fe from Gt=40%). Goethite (alpha-FeOOH) is mineralogical evidence for aqueous processes because it has structural hydroxide and is formed under aqueous conditions. Relatively unaltered basaltic soils (Fe(3+)/Fe(sub T) approx. 0.3) occur throughout Gusev crater (approx. 60-80% Fe from Ol+Px, approx. 10-30% from npOx, and approx. 10% from Mt). PasoRobles soil in the Columbia Hills has a unique occurrence of high concentrations of Fe(3+)-sulfate (approx. 65% of Fe). Magnetite is identified as a strongly magnetic phase in Martian soil and dust.
TL;DR: A route and mechanism for translocation of the capsular polysaccharide of Wza, an integral outer membrane lipoprotein, which is essential for group 1 capsule export in Escherichia coli is proposed and may provide insight into the export of other large polar molecules such as DNA and proteins.
Abstract: Many types of bacteria produce extracellular polysaccharides (EPSs). Some are secreted polymers and show only limited association with the cell surface, whereas others are firmly attached to the cell surface and form a discrete structural layer, the capsule, which envelopes the cell and allows the bacteria to evade or counteract the host immune system. EPSs have critical roles in bacterial colonization of surfaces, such as epithelia and medical implants; in addition some EPSs have important industrial and biomedical applications in their own right. Here we describe the 2.26 A resolution structure of the 340 kDa octamer of Wza, an integral outer membrane lipoprotein, which is essential for group 1 capsule export in Escherichia coli. The transmembrane region is a novel alpha-helical barrel. The bulk of the Wza structure is located in the periplasm and comprises three novel domains forming a large central cavity. Wza is open to the extracellular environment but closed to the periplasm. We propose a route and mechanism for translocation of the capsular polysaccharide. This work may provide insight into the export of other large polar molecules such as DNA and proteins.
TL;DR: Modulating the phases and amplitudes of the spectral components in the photoexcitation pulse showed that the absolute quantity of 13-cis retinal formed upon excitation can be enhanced or suppressed by ±20% of the yield observed using a short transform-limited pulse having the same actinic energy.
Abstract: Optical control of the primary step of photoisomerization of the retinal molecule in bacteriorhodopsin from the all-trans to the 13-cis state was demonstrated under weak field conditions (where only 1 of 300 retinal molecules absorbs a photon during the excitation cycle) that are relevant to understanding biological processes. By modulating the phases and amplitudes of the spectral components in the photoexcitation pulse, we showed that the absolute quantity of 13-cis retinal formed upon excitation can be enhanced or suppressed by ±20% of the yield observed using a short transform-limited pulse having the same actinic energy. The shaped pulses were shown to be phase-sensitive at intensities too low to access different higher electronic states, and so these pulses apparently steer the isomerization through constructive and destructive interference effects, a mechanism supported by observed signatures of vibrational coherence. These results show that the wave properties of matter can be observed and even manipulated in a system as large and complex as a protein.
TL;DR: This study employed DNA barcoding to examine Hyalella, a taxonomically difficult genus of amphipod crustaceans from sites in the southern Great Basin of California and Nevada, USA, and revealed extraordinary levels of cryptic diversity and endemism.
Abstract: DNA barcoding has revealed unrecognized species in several animal groups. In this study we have employed DNA barcoding to examine Hyalella, a taxonomically difficult genus of amphipod crustaceans, from sites in the southern Great Basin of California and Nevada, USA. We assessed the extent of species diversity using a species screening threshold (SST) set at 10 times the average intrapopulation cytochrome c oxidase subunit I (COI) haplotype divergence. Despite the fact that this threshold approach is more conservative in delineating provisional species than the phylogenetic species concept, our analyses revealed extraordinary levels of cryptic diversity and endemism. The SST discriminated two provisional species within Hyalella sandra, and 33 provisional species within Hyalella azteca. COI nucleotide divergences among these provisional species ranged from 4.4% to 29.9%. These results have important implications for the conservation of life in desert springs - habitats that are threatened as a result of groundwater over-exploitation.
TL;DR: The geographic range of I. scapularis-borne zoonoses may, therefore, expand significantly northwards as a consequence of climate change this century.
TL;DR: Analysis of over 10 000 rbcL sequences from GenBank demonstrate that this locus could serve well as the core region, with sufficient variation to discriminate among species in approximate ranges, and a tiered approach wherein highly variable loci are nested under a core barcoding gene is proposed.
Abstract: DNA barcoding based on the mitochondrial cytochrome c oxidase 1 (cox1) sequence is being employed for diverse groups of animals with demonstrated success in species identification and new species discovery. Applying barcoding systems to land plants will be a more challenging task as plant genome substitution rates are considerably lower than those observed in animal mitochondria, suggesting that a much greater amount of sequence data from multiple loci will be required to barcode plants. In the absence of an obvious well-characterized plant locus that meets all the necessary criteria, a key first step will be identifying candidate regions with the most potential. To meet the challenges with land plants, we are proposing the adoption of a tiered approach wherein highly variable loci are nested under a core barcoding gene. Analysis of over 10 000 rbcL sequences from GenBank demonstrate that this locus could serve well as the core region, with sufficient variation to discriminate among species in approximate...
TL;DR: The degree to which introductions of mycorrhizal fungi may lead to unintended negative, and potentially costly, consequences is assessed and appropriate management guidelines are made and top priority research needs are highlighted.
Abstract: Advances in ecology during the past decade have led to a much more detailed understanding of the potential negative consequences of species' introductions. Moreover, recent studies of mycorrhizal symbionts have led to an increased knowledge of the potential utility of fungal inoculations in agricultural, horticultural and ecological management. The intentional movement of mycorrhizal fungal species is growing, but the concomitant potential for negative ecological consequences of invasions by mycorrhizal fungi is poorly understood. We assess the degree to which introductions of mycorrhizal fungi may lead to unintended negative, and potentially costly, consequences. Our purpose is to make recommendations regarding appropriate management guidelines and highlight top priority research needs. Given the difficulty in discerning invasive species problems associated with mycorrhizal inoculations, we recommend the following. First, careful assessment documenting the need for inoculation, and the likelihood of success, should be conducted prior to inoculation because inoculations are not universally beneficial. Second, invasive species problems are costly and often impossible to control by the time they are recognized. We recommend using local inoculum sources whenever possible. Third, non-sterile cultures of inoculum can result in the movement of saprobes and pathogens as well as mutualists. We recommend using material that has been produced through sterile culture when local inoculum is not available. Finally, life-history characteristics of inoculated fungi may provide general guidelines relative to the likelihood of establishment and spread. We recommend that, when using non-local fungi, managers choose fungal taxa that carry life-history traits that may minimize the likelihood of deleterious invasive species problems. Additional research is needed on the potential of mycorrhizal fungi to spread to non-target areas and cause ecological damage.