bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fine‐scale population genetic structure of a wildlife disease vector: the southern house mosquito on the island of Hawaii
Authors: KEYGHOBADI NUSHA , LaPOINTE DENNIS , FLEISCHER ROBERT C. , FONSECA DINA M. 
Published: August 2006

AbstractThe southern house mosquito, Culex quinquefasciatus, is a widespread tropical and subtropical disease vector. In the Hawaiian Islands, where it was introduced accidentally almost two centuries ago, it is considered the primary vector of avian malaria and pox. Avian malaria in particular has contributed to the extinction and endangerment of Hawaii's native avifauna, and has altered the altitudinal distribution of native bird populations. We examined the population genetic structure of Cx. quinquefasciatus on the island of Hawaii at a smaller spatial scale than has previously been attempted, with particular emphasis on the effects of elevation on population genetic structure. We found significant genetic differentiation among populations and patterns of isolation by distance within the island. Elevation per se did not have a limiting effect on gene flow; however, there was significantly lower genetic diversity among populations at mid elevations compared to those at low elevations. A recent sample taken from just above the predicted upper altitudinal distribution of Cx. quinquefasciatus on the island of Hawaii was confirmed as being a temporary summer population and appeared to consist of individuals from more than one source population. Our results indicate effects of elevation gradients on genetic structure that are consistent with known effects of elevation on population dynamics of this disease vector.
Molecular and phenotypic divergence in the bluethroat (Luscinia svecica) subspecies complex
Authors: JOHNSEN ARILD , ANDERSSON STAFFAN , FERNANDEZ JAVIER GARCIA , KEMPENAERS BART , PAVEL VÁCLAV , QUESTIAU SOPHIE , RAESS MICHAEL , RINDAL EIRIK , LIFJELD JAN T. 
Published: August 2006

AbstractSubspecies complexes may provide valuable insights into the early stages of the speciation process. The bluethroat (Luscinia svecica) consists of many morphologically distinct subspecies that differ most strikingly in the ornamental colour pattern of the male throat. We investigated the genetic and phenotypic differentiation in this subspecies complex, using (i) microsatellite genotyping (11 loci) of a sample of 364 individuals from bluethroat populations in Europe and Asia, and (ii) spectrometric and morphological measurements of a sample of 131 museum skin specimens. Population genetic analyses, based on microsatellite allele frequency variation, revealed a slight but significant overall population differentiation (FST = 0.042). There was a well‐differentiated southern group of subspecies with white or no throat spots and a less‐differentiated northern group of chestnut‐spotted populations. Phylogenetic analyses indicated that the southern all‐blue and white‐spotted forms are ancestral to the chestnut‐spotted subspecies. In addition to the qualitative variation in throat plumage pattern already described in the literature, we found significant quantitative variation among subspecies in hue, chroma and brightness of the ultraviolet (UV)/blue throat coloration, and this variation seemed to be unrelated to the phylogenetic distance between subspecies.
Multiple paternity in a salamander with socially monogamous behaviour
Authors: LIEBGOLD ERIC B. , CABE PAUL R. , JAEGER ROBERT G. , LEBERG PAUL L. 
Published: August 2006

AbstractIn the majority of birds and mammals, social monogamy is not congruent with genetic monogamy. No research to date has compared social and genetic monogamy in amphibians. We analysed paternity in clutches of red‐backed salamanders (Plethodon cinereus), a species in which social monogamy has been demonstrated in the laboratory, and 28% of individuals in the forest are found in male‐female pairs in the noncourtship season. We collected 16 clutches of eggs ofP. cinereus in the southern Appalachian Mountains of Virginia and collected tail clippings from attending mothers. We genotyped embryos and adults at five microsatellite loci in order to analyse paternity of clutches. Most clutches (84.6%) had multiple sires, with two to three sires per clutch. In this study, 25% of clutches had males in addition to females attending eggs. None of the mothers of these clutches were genetically monogamous. All attending males sired some of the offspring in the clutch that they attended (between 9% and 50%) but never sired a majority in that clutch. We conclude that, at least in this population, social monogamy inP. cinereusis not concomitant with genetic monogamy.
Cryptic biodiversity and phylogeographical patterns in a snapping shrimp species complex
Authors: MATHEWS LAUREN M. 
Published: August 2006

AbstractRecent investigations suggest that marine biodiversity may be much higher than earlier estimates, and an important hidden source of diversity in marine systems is the phenomenon of cryptic species complexes. Such complexes are informative models for research into the evolutionary processes that govern species compositions of marine fauna. The snapping shrimp generaAlpheusandSynalpheusare known to harbour large numbers of cryptic species; here, I characterize the genetic structure of theAlpheus armillatusspecies complex in the northern Caribbean, west Atlantic, and Gulf of Mexico using mitochondrial and nuclear sequence data. Over this geographical region, the complex harbours at least three lineages that are probable reproductively isolated species; all major lineages diverged subsequent to the close of the Isthmus of Panama. Only one lineage was present in the Gulf of Mexico, whereas outside the Gulf of Mexico there was no clear tendency for lineage dominance by geographical region, as most sites were populated by shrimp from at least two lineages. However, within each lineage, there was strong evidence of population genetic differentiation between geographical regions. All lineages showed strong signals of demographic expansion, and one lineage showed sharply reduced genetic diversity, suggestive of past population bottlenecks or recently founded populations with low gene flow from other sites. These results show that evolutionary processes leading to divergence and speciation have been common and recent in the snapping shrimp, and suggest that connectivity among shrimp populations may be limited.
Phylogeography of the endangered Cathaya argyrophylla (Pinaceae) inferred from sequence variation of mitochondrial and nuclear DNA
Authors: WANG HONG‐WEI , GE SONG 
Published: August 2006

AbstractCathaya argyrophylla is an endangered conifer restricted to subtropical mountains of China. To study phylogeographical pattern and demographic history of C. argyrophylla, species‐wide genetic variation was investigated using sequences of maternally inherited mtDNA and biparentally inherited nuclear DNA. Of 15 populations sampled from all four distinct regions, only three mitotypes were detected at two loci, without single region having a mixed composition (GST = 1). Average nucleotide diversity (θws = 0.0024; πs = 0.0029) across eight nuclear loci is significantly lower than those found for other conifers (θws = 0.003∼0.015; πs = 0.002∼0.012) based on estimates of multiple loci. Because of its highest diversity among the eight nuclear loci and evolving neutrally, one locus (2009) was further used for phylogeographical studies and eight haplotypes resulting from 12 polymorphic sites were obtained from 98 individuals. All the four distinct regions had at least four haplotypes, with the Dalou region (DL) having the highest diversity and the Bamian region (BM) the lowest, paralleling the result of the eight nuclear loci. An AMOVA revealed significant proportion of diversity attributable to differences among regions (13.4%) and among populations within regions (8.9%). FST analysis also indicated significantly high differentiation among populations (FST = 0.22) and between regions (FST = 0.12–0.38). Non‐overlapping distribution of mitotypes and high genetic differentiation among the distinct geographical groups suggest the existence of at least four separate glacial refugia. Based on network and mismatch distribution analyses, we do not find evidence of long distance dispersal and population expansion in C. argyrophylla. Ex situ conservation and artificial crossing are recommended for the management of this endangered species.
A new ferrous iron‐uptake transporter, EfeU (YcdN), from Escherichia coli
Authors: Große Cornelia , Scherer Judith , Koch Doreen , Otto Markus , Taudte Nadine , Grass Gregor 
Published: August 2006

Summary Escherichia coli possesses multiple routes for iron uptake. Here we present EfeU (YcdN), a novel iron acquisition system of E. coli strain Nissle 1917. Laboratory strains of E. coli such as K12 lack a functional (efeU) ycdN gene caused by a frameshift mutation. EfeU, a member of the oxidase‐dependent iron transporters (OFeT), is a homologue of the iron permease Ftr1p from yeast. The ycdN gene is part of the ycdNOB tricistronic operon which is expressed in response to iron deprivation in a Fur‐dependent manner. Expression of efeU resulted in improved growth of an E. coli mutant lacking all known iron‐uptake systems and mediated increased iron uptake into cells. Furthermore, the presence of other divalent metal cations did not impair growth of strains expressing efeU. The EfeU protein functioned as ferrous iron permease in proteoliposomes in vitro. Topology analysis indicated that EfeU is an integral cytoplasmic membrane protein exhibiting seven transmembrane helices. Two REXXE motifs within transmembrane helices of OFeT family members are implicated in iron translocation. Site‐directed mutagenesis of each REGLE motif of EfeU diminished iron uptake in vivo and growth yield. In vitro the EfeU variant protein with an altered first REGLE motif was impaired in iron permeation, whereas activity of the EfeU variant with a mutation in the second motif was similar to the wild‐type protein.
Structural and biochemical characterization of gentisate 1,2‐dioxygenase from Escherichia coli O157:H7
Authors: Adams Melanie A. , Singh Vinay K. , Keller Bernd O. , Jia Zongchao 
Published: August 2006

SummaryGentisic acid (2,5‐dihydroxybenzoic acid) is a key intermediate in aerobic bacterial pathways that are responsible for the metabolism of a large number of aromatic compounds. The critical step of these pathways is the oxygen‐dependent reaction catalysed by gentisate 1,2‐dioxygenase which opens the aromatic ring of gentisate to form maleylpyruvate. From gentisic acid, the cell derives carbon and energy through the conversion of maleylpyruvate to central metabolites. We have confirmed the annotation of a gentisate 1,2‐dioygenase from the pathogenic O157:H7 Escherichia coli strain and present the first structural characterization of this family of enzymes. The identity of the reaction product was revealed using tandem mass spectroscopy. The operon responsible for the degradation of gentisate in this organism exhibits a high degree of conservation with the gentisate‐degrading operons of other pathogenic bacteria, including the Shiga toxin‐producing E. coli O103:H2, but does not appear to be present in non‐pathogenic strains. The acquisition of the gentisate operon may represent a special adaptation to meet carbon source requirements under conditions of environmental stress and may provide a selective advantage for enterohaemorrhagic E. coli relative to their non‐pathogenic counterparts.
The peroxisomal import proteins PEX2, PEX5 and PEX7 are differently involved in Podospora anserina sexual cycle
Authors: Bonnet Crystel , Espagne Eric , Zickler Denise , Boisnard Stéphanie , Bourdais Anne , Berteaux‐Lecellier Véronique 
Published: August 2006

SummaryPEX5, PEX7 and PEX2 are involved in the peroxisomal matrix protein import machinery. PEX5 and PEX7 are the receptors for the proteins harbouring, respectively, a PTS1 and a PTS2 peroxisomal targeting sequence and cycle between the cytoplasm and the peroxisome. PEX2 belongs to the RING‐finger complex located in the peroxisomal membrane and acts in protein import downstream of PEX5 and PEX7; it is therefore required for the import of both PTS1 and PTS2 proteins. We have shown previously that PEX2 deficiency leads to an impairment of meiotic commitment in the filamentous fungus Podospora anserina. Here we report that both PEX5 and PEX7 receptors are dispensable for this commitment but are needed for normal sexual cycle. Data suggest also a new role of PEX2 and/or the RING‐finger complex in addition to their role in PTS1 and PTS2 import. Strikingly, Δpex5 and Δpex7 single and double knockout strains analyses indicate that Δpex7 acts as a partial suppressor of Δpex5 life cycle deficiencies. Moreover, contrary to pex2 mutants, Δpex5 and Δpex7 show mitochondrial morphological abnormalities.
A novel signal transduction system and feedback loop regulate fructan hydrolase gene expression in Streptococcus mutans
Authors: Zeng Lin , Wen Zezhang T. , Burne Robert A. 
Published: August 2006

SummaryThe fruA gene of Streptococcus mutans encodes for a secreted fructan hydrolase (fructanase), an established virulence determinant required for releasing d‐fructose from levan‐ and inulin‐type fructans. Expression of fruA is under the control of carbon catabolite repression and is induced by growth in fructans. In this report, we identified an operon in S. mutans UA159 encoding a two‐component system flanked by two predicted carbohydrate‐binding proteins that is absolutely required for the expression of fruA. All four genes were found to be required for optimal growth of S. mutans on inulin‐containing medium and for transcriptional activation of fruA. Complementation assays using a plasmid expressing the response regulator suggested that the two‐component system works in concert with the sugar‐binding proteins. This operon was also shown to activate a four‐gene cluster located immediately downstream and encoding an Enzyme II (EIILev) for a fructose/mannose sugar : phosphotransferase enzyme, which was found to negatively regulate the expression of fruA. Using transcriptional fusions, it was found that fructose could signal induction of the fruA and levD operons through the two‐component system/sugar‐binding protein complex. A recombinant LevR protein was shown to bind to the promoter regions of fruA and levD in gel mobility shift assays. Thus, a ‘four‐component signal transduction system’ activates fructan catabolism and the expression of an Enzyme II complex that functions in a feedback loop to sense the accumulation of the end‐product of fructan degradation.
The F‐box protein Grr1 regulates the stability of Ccn1, Cln3 and Hof1 and cell morphogenesis in Candida albicans
Authors: Li Wan Jie , Wang Yan Ming , Zheng Xin De , Shi Qing Mei , Zhang Ting Ting , Bai Chen , Li Di , Sang Jian Li , Wang Yue 
Published: August 2006

SummaryBoth G1 and mitotic cyclins have been implicated in regulating Candida albicans filamentous growth. We have investigated the functions of Grr1 whose orthologue in Saccharomyces cerevisiae is known to mediate ubiquitin‐dependent degradation of the G1 cyclins Cln1 and Cln2. Here, we report that deleting C. albicans GRR1 causes significant stabilization of two G1 cyclins Ccn1 and Cln3 and pseudohyphal growth. grr1Δ cells are highly heterogeneous in length and many of them fail to separate after cytokinesis. Interestingly, some isolated rod‐like G1 cells of similar sizes are present in the grr1Δ culture. Time‐lapse microscopy revealed that the rod‐shaped G1 cells first grew exclusively in width before budding and then the bud grew exclusively by apical extension until after cytokinesis, yielding rod‐like daughter cells. Consistently, actin patches persistently localize to the bud tip until around the time of cytokinesis. Despite the pseudohyphal phenotype, grr1Δ cells respond normally to hyphal induction. Hyperphosphorylated Cln3 isoforms accumulate in grr1Δ cells, indicating that Grr1 selectively mediates their degradation in wild‐type cells. grr1Δ pseudohyphal growth requires neither Hgc1 nor Swel, two important regulators of cell morphogenesis. Furthermore, the cellular level of Hof1, a protein having a role in cytokinesis, is also significantly increased in grr1Δ cells.
Implementing a comprehensive cost information system in rural health facilities: the case of Nouna health district, Burkina Faso
Authors: Flessa Steffen , Kouyaté Bocar 
Published: August 2006

SummaryObjectives  To present first findings of a cost‐of‐illness (COI) information system implemented in Nouna health district, Burkina Faso. The entire project will include household and provider tangible COI, whereas this article concentrates on the development of a provider cost information system in rural first‐line health facilities.Method  Special forms and reports are prepared to routinely collect capital and recurrent costs of first‐line facilities. Inventory lists are designed, and buildings and equipment are assessed by engineers. Total, fixed, variable and average costs are calculated for 15 rural health centres with five cost centres: general outpatient consultation, ambulatory nursing care, deliveries, immunization and other services (neonatal consultation, child care and family planning).Results  In 2003, the average costs per service unit were 1.34 US$ for a general consultation, 0.51 US$ for ambulatory nursing care, 6.73 US$ per delivery, 3.64 US$ per vaccination and 1.11 US$ per service unit of other care. On average, a health centre consumes 29 900 US$ per year for a catchment population of 10 000 inhabitants.Conclusions  The major share of costs is fixed and does not depend on the workload of the health centre. Consequently, the costs of first‐line facilities will hardly increase if the demand for health services rises. These findings can be used to improve the health financing in Nouna health district, Burkina Faso.
Detection of adult Brugia malayi filariae by ultrasonography in humans in India and Indonesia
Authors: Mand S. , Supali T. , Djuardi J. , Kar S. , Ravindran B. , Hoerauf A. 
Published: August 2006

SummaryIn bancroftian filariasis, ultrasonography (USG) is a suitable tool to monitor infection by the detection of adult filariae in addition to antigen detection tests (ICT, Og4C3). However, in brugian filariasis, ultrasound examinations in humans have so far failed to detect adult worms and no antigen test is available to verify infections in patients who are carriers of adult worms but amicrofilaraemic. In this study, we describe the feasibility of detection of adult Brugia malayi filariae by USG. Worm nests were detected in 4 of 32 patients in India and Indonesia, located in the breast, the thigh, the calf and an inguinal lymph node. The study shows that adult filariae of B. malayi in humans can be detected by USG, but the technique is limited by the fact that worm nests seem not to be stable over time in humans, as is the case in bancroftian filariasis.
Genotype‐by‐environment interactions leads to variable selection on life‐history strategy in Common Evening Primrose (Oenothera biennis)
Authors: JOHNSON M. T. J. 
Published: August 2006

AbstractMonocarpic plant species, where reproduction is fatal, frequently exhibit variation in the length of their prereproductive period prior to flowering. If this life‐history variation in flowering strategy has a genetic basis, genotype‐by‐environment interactions (G × E) may maintain phenotypic diversity in flowering strategy. The native monocarpic plant Common Evening Primrose (Oenothera biennis L., Onagraceae) exhibits phenotypic variation for annual vs. biennial flowering strategies. I tested whether there was a genetic basis to variation in flowering strategy in O. biennis, and whether environmental variation causes G × E that imposes variable selection on flowering strategy. In a field experiment, I randomized more than 900 plants from 14 clonal families (genotypes) into five distinct habitats that represented a natural productivity gradient. G × E strongly affected the lifetime fruit production of O. biennis, with the rank‐order in relative fitness of genotypes changing substantially between habitats. I detected genetic variation in annual vs. biennial strategies in most habitats, as well as a G × E effect on flowering strategy. This variation in flowering strategy was correlated with genetic variation in relative fitness, and phenotypic and genotypic selection analyses revealed that environmental variation resulted in variable directional selection on annual vs. biennial strategies. Specifically, a biennial strategy was favoured in moderately productive environments, whereas an annual strategy was favoured in low‐productivity environments. These results highlight the importance of variable selection for the maintenance of genetic variation in the life‐history strategy of a monocarpic plant.
Male mating preferences pre‐date the origin of a female trait polymorphism in an incipient species complex of Lake Victoria cichlids
Authors: PIEROTTI M. E. R. , SEEHAUSEN O. 
Published: August 2006

AbstractDisruptive sexual selection on colour patterns has been suggested as a major cause of diversification in the cichlid species flock of Lake Victoria. InNeochromis omnicaeruleus, a colour and sex determination polymorphism is associated with a polymorphism in male and female mating preferences. Theoretical work on this incipient species complex found conditions for rapid sympatric speciation by selection on sex determination and sexual selection on male and female colour patterns, under restrictive assumptions. Here we test the biological plausibility of a key assumption of such models, namely, the existence of a male preference against a novel female colour morph before its appearance in the population. We show that most males in a population that lacks the colour polymorphism exhibit a strong mating preference against the novel female colour morph and that reinforcement is not a likely explanation for the origin of such male preferences. Our results show that a specific condition required for the combined action of selection on sex determination and sexual selection to drive sympatric speciation is biologically justified. Finally, we suggest that Lake Victoria cichlids might share an ancestral female recognition scheme, predisposing colour monomorphic populations/species to similar evolutionary pathways leading to divergence of colour morphs in sympatry.
Comparison of Three Diagnostic Detection Methods for Tuberculosis in French Cattle
Authors: Watrelot‐Virieux D. , Drevon‐Gaillot E. , Toussaint Y. , Belli P. 
Published: August 2006

SummaryThree additional techniques (Ziehl–Neelsen, auramine O/rhodamine and immunostaining using polyclonal anti‐Mycobacterium bovis) to hematoxylin‐eosin histopathology were evaluated for bovine tuberculosis diagnosis on 39 samples from several slaughterhouses. The immunohistochemichal technique was more sensitive and could detect a greater number of positive cattle. It has about the same sensibility as the bacteriology but it was faster.