Different Hosts (different + hosts)

Distribution by Scientific Domains
Distribution within Life Sciences


Selected Abstracts


Gastrointestinal Bacterial Transmission among Humans, Mountain Gorillas, and Livestock in Bwindi Impenetrable National Park, Uganda

CONSERVATION BIOLOGY, Issue 6 2008
INNOCENT B. RWEGO
ecología de enfermedades; Escherichia coli; primates; salud del ecosistema; zoonosis Abstract:,Habitat overlap can increase the risks of anthroponotic and zoonotic pathogen transmission between humans, livestock, and wild apes. We collected Escherichia coli bacteria from humans, livestock, and mountain gorillas (Gorilla gorilla beringei) in Bwindi Impenetrable National Park, Uganda, from May to August 2005 to examine whether habitat overlap influences rates and patterns of pathogen transmission between humans and apes and whether livestock might facilitate transmission. We genotyped 496 E. coli isolates with repetitive extragenic palindromic polymerase chain reaction fingerprinting and measured susceptibility to 11 antibiotics with the disc-diffusion method. We conducted population genetic analyses to examine genetic differences among populations of bacteria from different hosts and locations. Gorilla populations that overlapped in their use of habitat at high rates with people and livestock harbored E. coli that were genetically similar to E. coli from those people and livestock, whereas E. coli from gorillas that did not overlap in their use of habitats with people and livestock were more distantly related to human or livestock bacteria. Thirty-five percent of isolates from humans, 27% of isolates from livestock, and 17% of isolates from gorillas were clinically resistant to at least one antibiotic used by local people, and the proportion of individual gorillas harboring resistant isolates declined across populations in proportion to decreasing degrees of habitat overlap with humans. These patterns of genetic similarity and antibiotic resistance among E. coli from populations of apes, humans, and livestock indicate that habitat overlap between species affects the dynamics of gastrointestinal bacterial transmission, perhaps through domestic animal intermediates and the physical environment. Limiting such transmission would benefit human and domestic animal health and ape conservation. Resumen:,El traslape de hábitats puede incrementar los riesgos de transmisión de patógenos antroponótica y zoonótica entre humanos, ganado y simios silvestres. Recolectamos bacterias Escherichia coli de humanos, ganado y gorilas de montaña (Gorilla gorilla beringei) en el Parque Nacional Bwindi Impenetrable, Uganda, de mayo a agosto 2005 para examinar sí el traslape de hábitat influye en las tasas y patrones de transmisión de patógenos entre humanos y simios y sí el ganado facilita esa transmisión. Determinamos el genotipo de 496 aislados de E. coli con marcaje de reacción en cadena de polimerasa palindrómica extragénica (rep-PCR) y medimos la susceptibilidad a 11 antibióticos con el método de difusión de disco. Realizamos análisis de genética poblacional para examinar las diferencias genéticas entre poblaciones de bacterias de huéspedes y localidades diferentes. Las poblaciones de gorilas con alto grado de traslape en el uso de hábitat con humanos y ganado presentaron E. coli genéticamente similar a E. coli de humanos y ganado, mientras que E. coli de gorilas sin traslape en el uso hábitat con humanos y ganado tuvo relación lejana con las bacterias de humanos y ganado. Treinta y cinco porciento de los aislados de humanos, 27% de los aislados de ganado y 17% de los aislados de gorilas fueron clínicamente resistentes a por lo menos un antibiótico utilizado por habitantes locales, y la proporción de gorilas individuales con presencia de aislados resistentes declinó en las poblaciones proporcionalmente con la disminución en el grado de traslape con humanos. Estos de patrones de similitud genética y resistencia a antibióticos entre E. coli de poblaciones de simios, humanos y ganado indican que el traslape de hábitat entre especies afecta la dinámica de transmisión de bacterias gastrointestinales, probablemente a través de animales domésticos intermediarios y el ambiente físico. La limitación de esa transmisión beneficiaría a la salud de humanos y animales domésticos y a la conservación de simios. [source]


Ascomycetes associated with ectomycorrhizas: molecular diversity and ecology with particular reference to the Helotiales

ENVIRONMENTAL MICROBIOLOGY, Issue 12 2009
Leho Tedersoo
Summary Mycorrhizosphere microbes enhance functioning of the plant,soil interface, but little is known of their ecology. This study aims to characterize the ascomycete communities associated with ectomycorrhizas in two Tasmanian wet sclerophyll forests. We hypothesize that both the phyto- and mycobiont, mantle type, soil microbiotope and geographical distance affect the diversity and occurrence of the associated ascomycetes. Using the culture-independent rDNA sequence analysis, we demonstrate a high diversity of these fungi on different hosts and habitats. Plant host has the strongest effect on the occurrence of the dominant species and community composition of ectomycorrhiza-associated fungi. Root endophytes, soil saprobes, myco-, phyto- and entomopathogens contribute to the ectomycorrhiza-associated ascomycete community. Taxonomically these Ascomycota mostly belong to the orders Helotiales, Hypocreales, Chaetothyriales and Sordariales. Members of Helotiales from both Tasmania and the Northern Hemisphere are phylogenetically closely related to root endophytes and ericoid mycorrhizal fungi, suggesting their strong ecological and evolutionary links. Ectomycorrhizal mycobionts from Australia and the Northern Hemisphere are taxonomically unrelated to each other and phylogenetically distant to other helotialean root-associated fungi, indicating independent evolution. The ubiquity and diversity of the secondary root-associated fungi should be considered in studies of mycorrhizal communities to avoid overestimating the richness of true symbionts. [source]


Application of nr-DNA ITS sequence for identification of Fusarium culmorum isolates,

EPPO BULLETIN, Issue 3-4 2000
P. K. Mishra
Variation within the internal transcribed spacers (ITS1 and ITS2) and 5.8S ribosomal DNA region of 60 Fusarium culmorum isolates (section Discolor), representing different hosts and diverse geographical origins was examined by polymerase chain reaction (PCR), coupled with sequencing. Phylogenetic relationships of these F. culmorum isolates were estimated in relation to Fusarium spp. from this and other sections of the form-genus, using sequences available from Genbank. The amplified ITS region was approximately 570 bp long in 56 isolates and approximately 585 bp in four other isolates. The inferred phylogeny distinguished clearly four isolates supplied as F. culmorum. These isolates differed in both morphology and sequence from the remaining F. culmorum material. Sequence analysis revealed that the remaining 56 isolates were divided into three ITS types, within which the divergence was extremely low. ITS sequence comparison among the Fusarium isolates showed two major clades, one comprising sections Discolor, Sporotrichiella and Gibbosum and the other comprising Elegans, Liseola, Martiella and Roseum. These results demonstrate the use of the ITS region to resolve the identification and taxonomic problems of Fusarium spp. especially at sectional level but demonstrate the need to develop some other molecular markers for identification at the level of species or race. [source]


Ericoid mycorrhizal fungi are common root inhabitants of non- Ericaceae plants in a south-eastern Australian sclerophyll forest

FEMS MICROBIOLOGY ECOLOGY, Issue 2 2008
Susan M. Chambers
Abstract Fungi were isolated from the roots of 17 plant species from the families Apiaceae, Cunoniaceae, Cyperaceae, Droseraceae, Fabaceae-Mimosoideae, Lomandraceae, Myrtaceae, Pittosporaceae, Proteaceae and Stylidiaceae at a sclerophyll forest site in New South Wales, Australia. Internal transcribed spacer (ITS) restriction fragment length polymorphism (RFLP) and sequence comparisons indicated that the isolated fungi had affinities to a range of ascomycetes, basidiomycetes and zygomycetes. Four RFLP types had closest affinities to previously identified Helotiales ericoid mycorrhizal (ERM) or Oidiodendron spp. Isolates representing six RFLP types, which were variously isolated from all 17 plant species, formed ERM coils in hair root epidermal cells of Woollsia pungens (Ericaceae) under gnotobiotic conditions. Three of these isolates formed intercellular hyphae, intracellular hyphae and/or microsclerotia, which are typical of dark septate endophyte infection, in roots of Stylidium productum (Stylidiaceae), indicating an ability to form different types of association with roots of different hosts. Overall the data indicate that a broad range of plant taxa may act as repositories for ERM fungi in sclerophyll forest soil. [source]


Spent media from cultures of environmental isolates of Escherichia coli can suppress the deficiency of biofilm formation under anoxic conditions of laboratory E. coli strains

FEMS MICROBIOLOGY ECOLOGY, Issue 3 2006
Tecilli Cabellos-Avelar
Abstract The prevailing lifestyle of bacteria is sessile and they attach to surfaces in structures known as biofilms. In Escherichia coli, as in many other bacteria, biofilms are formed at the air-liquid interface, suggesting that oxygen has a critical role in the biofilm formation process. It has been reported that anaerobically growing E. coli laboratory strains are unable to form biofilms even after 96 h of incubation on Luria Bertani (LB) medium. After analyzing 22 000 transposon-induced and 26 000 chemically-induced mutants we failed to isolate an E. coli laboratory strain with the ability to form biofilm under anaerobic growth conditions. Notably, seven strains from a collection of E. coli isolated from different hosts and the environment had the ability to form biofilm in the absence of oxygen. Interestingly, spent medium from cultures of one strain, Souza298, can promote biofilm formation of E. coli laboratory strains growing under anaerobic conditions. Our results led us to propose that laboratory E. coli strains do not release (or synthesize) a molecule needed for biofilm formation under anoxic conditions but that they bear all the required machinery needed for this process. [source]


Development of microsatellite markers for Pythium helicoides

FEMS MICROBIOLOGY LETTERS, Issue 1 2009
Yin-Ling
Abstract A strategy combining dual-suppression PCR and thermal asymmetric interlaced PCR was used to determine sequences flanking microsatellite regions in Pythium helicoides. The primer pairs were designed to amplify loci containing (AC)n, (GA)n, (AGC)n, (CAC)n(CAA)n, (TCA)n and (CTTT)n repeats from the P. helicoides nuclear genome. The PCR products of each primer pair, amplified from three representative isolates collected from different hosts and locations, were cloned and sequenced. Different degrees of polymorphism were detected among these microsatellite markers. The numbers of alleles were 6, 2, 4, 11, 4 and 4 in YL-AC, YL-AGC, YL-CAA, YL-CTTT, YL-GA and YL-TCA, respectively. Allele analysis of 30 P. helicoides isolates showed length polymorphisms in all loci, except for YL-AC, using capillary electrophoresis. Thus, we have developed a simple method for designing PCR primers to amplify microsatellite markers from P. helicoides. [source]


High Efficiency Blue Organic LEDs Achieved By an Integrated Fluorescence,Interlayer,Phosphorescence Emission Architecture

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010
Tianhang Zheng
Abstract This paper presents a new strategy to develop efficient organic light-emitting devices (OLEDs) by doping fluorescent- and phosphorescent-type emitters individually into two different hosts separated by an interlayer to form a fluorescence,interlayer,phosphorescence (FIP) emission architecture. One blue OLED with FIP emission structure comprising p -bis(p - N,N -diphenylaminostyryl)benzene (DSA-Ph) and bis[(4,6-di-fluorophenyl)-pyridinate- N,C2']picolinate (FIrpic) exhibiting a peak luminance efficiency of 15.8,cd A,1 at 1.54,mA cm,2 and a power efficiency of 10.2,lm W,1 at 0.1,mA cm,2 is successfully demonstrated. The results are higher than those of typical phosphorescent OLEDs with a single emission layer by 34% and 28%, respectively. From experimental and theoretical investigations on device performance, and the functions of the used emitters and interlayer, such enhancement should ascribe to the appropriate utilization of the two types of emitters. The fluorescent emitter of DSA-Ph is used to facilitate the carrier transport, and thus accelerate the generation of excitons, while the phosphorescent emitter of FIrpic could convert the generated excitons into light efficiently. The method proposed here can be applied for developing other types of red, green, and white OLEDs. [source]


Susceptibility of cones and seeds to fungal infection in a pine (Pinus spp.) collection

FOREST PATHOLOGY, Issue 6 2000
V. Vujanovic
Summary Thirty-one fungi, members of Ascomycota and Deuteromycota, were isolated from cones/seeds of 28 hosts (Pinus spp.) originating from East Asia, Europe and North America, and growing at the Montreal Botanical Garden, Canada. A total of 21 taxa of these isolated fungi are considered pathogens. The damage severity was most prevalent on Diploxylon pines of European provenance (Pinus nigra, Pinus mugo and Pinus sylvestris), and one indigenous North American species (Pinus albicaulis). Twelve fungi occurred on different hosts, i.e. Sphaeropsis sapinea (12), Herpotrichia juniperi (8), Truncatella hartigii (7), Ceuthospora sp. (5), Fusarium, spp. (5), Pestalotiopsis funerea (3), Phomopsis sp. (3), Valsa spp. (anamorph. Cytospora) (3), Diaporthe sp. (3), Fusicoccum sp. (2) and Sirococcus strobilinus (2). Sphaeropsis sapinea, Herpotrichia juniperi, Phomopsis conorum, Truncatella hartigii, Tubercularia sp. and Valsa spp. were related to high cone and seed damage. For the most frequently observed Sphaeropsis sapinea damage, the subgenus Haploxylon was less susceptible than Diploxylon, and P. sylvestris less than P. nigra and P. mugo. Pinus resinosa showed more tolerance to S. sapinea. Truncatella hartigii was more frequently associated with necrotic lesions on cones/seeds in comparison with Pestalotiopsis funerea. The results are discussed in the context of arboretum, seed orchard, nursery and quarantine management. [source]


The capacity of Salmonella to survive inside dendritic cells and prevent antigen presentation to T cells is host specific

IMMUNOLOGY, Issue 4 2008
Susan M. Bueno
Summary Infection with Salmonella enterica serovar Typhimurium (S. Typhimurium) causes a severe and lethal systemic disease in mice, characterized by poor activation of the adaptive immune response against Salmonella -derived antigens. Recently, we and others have reported that this feature relies on the ability of S. Typhimurium to survive within murine dendritic cells (DCs) and avoid the presentation of bacteria-derived antigens to T cells. In contrast, here we show that infection of murine DCs with either S. Typhi or S. Enteritidis, two serovars adapted to different hosts, leads to an efficient T-cell activation both in vitro and in vivo. Accordingly, S. Typhi and S. Enteritidis failed to replicate within murine DCs and were quickly degraded, allowing T-cell activation. In contrast, human DCs were found to be permissive for survival and proliferation of S. Typhi, but not for S. Typhimurium or S. Enteritidis. Our data suggest that Salmonella host restriction is characterized by the ability of these bacteria to survive within DCs and avoid activation of the adaptive immune response in their specific hosts. [source]


Are ectoparasite communities structured?

JOURNAL OF ANIMAL ECOLOGY, Issue 6 2006
Species co-occurrence, null models, temporal variation
Summary 1We studied temporal variation in the structure of flea communities on small mammalian hosts from eastern Slovakia using null models. We asked (a) whether flea co-occurrences in infracommunities (in the individual hosts) in different hosts as well as in the component communities (in the host species) demonstrate a non-random pattern; (b) whether this pattern is indicative of either positive or negative flea species interactions; (c) whether this pattern varies temporally; and (d) whether the expression of this pattern is related to population size of either fleas or hosts or both. 2We constructed a presence/absence matrix of flea species for each temporal sample of a host species and calculated four metrics of co-occurrence, namely the C -score, the number of checkerboard species pairs, the number of species combinations and the variance ratio (V -ratio). Then we compared these metrics with the respective indices calculated for 5000 null matrices that were assembled randomly using two algorithms, namely fixed-fixed (FF) and fixed-equiprobable (FE). 3Most co-occurrence metrics calculated for real data did not differ significantly from the metrics calculated for simulated matrices using the FF algorithm. However, the indices observed for 42 of 75 presence/absence matrices differed significantly from the null expectations for the FE models. Non-randomness was detected mainly by the C -score and V -ratio metrics. In all cases, the direction of non-randomness was the same, namely the aggregation, not competition, of flea species in host individuals and host species. 4The inclusion or exclusion of the uninfested hosts in the FE models did not affect the results for individual host species. However, exclusion of the uninfested host species led to the acceptance of the null hypothesis for only six of 13 temporal samples of the component flea communities for which non-randomness was detected when the uninfested hosts were included in the analysis. 5In most host species, the absolute values of the standardized size effect of both the C -score and V -ratio increased with an increase in host density and a concomitant decrease in flea abundance and prevalence. 6Results of this study demonstrated that (a) flea assemblages on small mammalian hosts were structured at some times, whereas they appeared to be randomly assembled at other times; (b) whenever non-randomness of flea co-occurrences was detected, it suggested aggregation but never segregation of flea species in host individuals or populations; and (c) the expression of structure in flea assemblages depended on the level of density of both fleas and hosts. [source]


Foraging behaviour of Helicoverpa armigera first instar larvae on crop plants of different developmental stages

JOURNAL OF APPLIED ENTOMOLOGY, Issue 5 2005
M.-L. Johnson
Abstract:, Understanding how insect pests forage on their food plants can help optimize management strategies. Helicoverpa armigera (Hübner) (Lep., Noctuidae) is a major polyphagous pest of agricultural crops worldwide. The immature stages feed and forage on crops at all stages of plant development, damaging fruiting and non-fruiting structures, yet very little is known about the influence of host type or stage on the location and behaviour of larvae. Through semi-continuous observation, we evaluated the foraging (movement and feeding) behaviours of H. armigera first instar larvae as well as the proportion of time spent at key locations on mungbean [Vigna radiata (L.) Wilczek] and pigeon pea [Cajanus cajan (L.) Millspaugh] of differing developmental stages: seedling- and mature (flowering/pod fill)-stage plants. Both host type and age affected the behaviour of larvae. Larvae spent more time in the upper parts of mature plants than on seedlings and tended to stay at the top of mature plants if they moved there. This difference was greater in pigeon pea than in mungbean. The proportion of time allocated to feeding on different parts of a plant differed with host and age. More feeding occurred in the top of mature pigeon pea plants but did not differ between mature and seedling mungbean plants. The duration of key behaviours did not differ between plant ages in either crop type and was similar between hosts although resting bouts were substantially longer on mungbeans. Thus a polyphagous species such as H. armigera does not forage in equivalent ways on different hosts in the first instar stage. [source]


Genetic characterization of Erwinia amylovora strains by amplified fragment length polymorphism

JOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2004
A. Rico
Abstract Aims:,Erwinia amylovora is one of the most important pathogens of pear and apple and is subject to strict quarantine regulations worldwide, although its patterns of dispersal are largely unknown. Previous attempts to fingerprint E. amylovora strains by molecular techniques have detected very little polymorphism because of the high genetic homogeneity of this bacterium. Our aim was to establish and test a typing method to quantify genetic diversity among strains of this plant pathogen. Methods and Results:, Twenty-two strains from different hosts and geographical locations were examined by PCR fingerprinting with four primers and by amplified fragment length polymorphism (AFLP) with four selected combinations of primers with a single base extension. PCR fingerprinting revealed little polymorphism producing the same amplification patterns for 17 strains, while the combined AFLP patterns yielded 78 polymorphic bands (34% of total bands) and allowed the differentiation of all but two strains. Clustering of strains in the resulting dendrogram was not correlated with host, year or country of isolation, and questions previous genealogies based on PFGE patterns. Conclusions:, The AFLP technique allowed the detection of an unprecedented number of genetic markers in E. amylovora and proved to be the most useful tool so far for discriminating among strains of this pathogen. The results obtained in this study strongly suggest the occurrence of multiple introductions of the pathogen in Spain and other European countries. Significance and Impact of the Study:, A major limitation in understanding the ecology of fire blight is the lack of typing techniques with a high power of discrimination. This study demonstrates the high resolution and the usefulness of the AFLP technique to differentiate among E. amylovora strains. [source]


Reproductive barriers between two sympatric beetle species specialized on different host plants

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 11 2009
H.-J. XUE
Abstract Knowledge on interspecific pre- and post-zygotic isolation mechanisms provides insights into speciation patterns. Using crosses (F1 and backcrosses) of two closely related flea beetles species, Altica fragariae and A. viridicyanea, specialized on different hosts in sympatry, we measured: (a) the type of reproductive isolation and (b) the inheritance mode of preference and host-specific performance, using a joint-scaling test. Each species preferred almost exclusively its host plant, creating strong prezygotic isolation between them, and suggesting that speciation may occur at least partly in sympatry. Reproductive isolation was intrinsic between females of A. fragariae and either A. viridicyanea or F1 males, whereas the other crosses showed ecologically dependent reproductive isolation, suggesting ecological speciation. The genetic basis of preference and performance was at least partially independent, and several loci coded for preference, which limits the possibility of sympatric speciation. Hence, both ecological and intrinsic factors may contribute to speciation between these species. [source]


Resource specialization in a phytophagous insect: no evidence for genetically based performance trade-offs across hosts in the field or laboratory

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2009
S. J. AGOSTA
Abstract We present a field test of the genetically based performance trade-off hypothesis for resource specialization in a population of the moth Rothschildia lebeau whose larvae primarily feed on three host plant species. Pairwise correlations between growth vs. growth, survival vs. survival and growth vs. survival across the different hosts were calculated, using families (sibships) as the units of analysis. Of 15 pairwise correlations, 14 were positive, 5 significantly so and none were negative. The same pattern was found using complementary growth and survival data from the laboratory. Overall, we found no evidence of negative genetic correlations in cross-host performance that would be indicative of performance trade-offs in this population. Rather, variation among families in performance appears to reflect ,general vigour' whereby families that perform well on one host perform well across multiple hosts. We discuss the implications of positive genetic correlations in cross-host performance in terms of the ecology and evolution of host range. We argue that this genetic architecture facilitates colonization of novel hosts and recolonization of historical hosts, therefore contributing to host shifts, host range expansions, biological invasions and introductions, and host ranges that are regionally broad but locally narrow. [source]


Genetic architecture for normal and novel host-plant use in two local populations of the herbivorous ladybird beetle, Epilachna pustulosa

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2003
H. Ueno
Abstract Trade-offs in host-plant use are thought to promote the evolution of host specificity. However, usually either positive or no genetic correlations have been found. Whereas factors enhancing variation in overall viability have been claimed to mask negative genetic correlations, alternative hypotheses emphasize the sequential changes in genetic correlation in the course of host-range evolution. In this study, the genetic architectures of performances on different hosts were compared in two populations of the herbivorous ladybird beetle, Epilachna pustulosa, using three host plants, one being normal for both, one novel for only one population, and the other novel for both populations. The genetic correlations between larval periods on normal hosts were significantly positive whereas those between normal and novel hosts were not different from zero. There was no evidence for reduced genetic variation on the normal host-plants. These results suggest that the host-range is not restricted by the antagonistic genetic associations among exploitation abilities on different plant species, but rather that selection of different host-plants may improve the coordination between genes responsible for the use of different plants. [source]


Validity of species status of the parasitic mite Otodectes cynotis

MEDICAL AND VETERINARY ENTOMOLOGY, Issue 2 2002
J. Lohse
Abstract A combined molecular and phenotypic approach was used to determine whether ear mites of the genus Otodectes (Acari: Psoroptidae) belong to a single species. The second internal transcribed spacer (ITS 2) of the rDNA of 16 isolates from 11 cats, two dogs, one arctic fox and two ferrets originating from four different continents was characterized. In addition, mites from dog, cat and arctic fox were investigated morphologically. Sequence comparisons revealed five different, but closely related genotypes which did not segregate according to host species or geographical origin. Morphologically, mites of the three host species did not differ significantly in their body or leg sizes. These investigations support the view that ear mites of the genus Otodectes from different hosts and geographical origins belong to a single species, Otodectes cynotis (Hering). [source]


Host-driven divergence in the parasitic plant Orobanche minor Sm. (Orobanchaceae)

MOLECULAR ECOLOGY, Issue 19 2008
C. J. THOROGOOD
Abstract Many parasitic angiosperms have a broad host range and are therefore considered to be host generalists. Orobanche minor is a nonphotosynthetic root parasite that attacks a range of hosts from taxonomically disparate families. In the present study, we show that O. minor sensu lato may comprise distinct, genetically divergent races isolated by the different ecologies of their hosts. Using a three-pronged approach, we tested the hypothesis that intraspecific taxa O. minor var. minor and O. minor ssp. maritima parasitizing either clover (Trifolium pratense) or sea carrot (Daucus carota ssp. gummifer), respectively, are in allopatric isolation. Morphometric analysis revealed evidence of divergence but this was insufficient to define discrete, host-specific taxa. Intersimple sequence repeat (ISSR) marker-based data provided stronger evidence of divergence, suggesting that populations were isolated from gene flow. Phylogenetic analysis, using sequence-characterized amplified region (SCAR) markers derived from ISSR loci, provided strong evidence for divergence by clearly differentiating sea carrot-specific clades and mixed-host clades. Low levels of intrapopulation SCAR marker sequence variation and floral morphology suggest that populations on different hosts are probably selfing and inbreeding. Morphologically cryptic Orobanche taxa may therefore be isolated from gene flow by host ecology. Together, these data suggest that host specificity may be an important driver of allopatric speciation in parasitic plants. [source]


Molecular diversity of arbuscular mycorrhizal fungi and patterns of host association over time and space in a tropical forest

MOLECULAR ECOLOGY, Issue 12 2002
R. Husband
Abstract We have used molecular techniques to investigate the diversity and distribution of the arbuscular mycorrhizal (AM) fungi colonizing tree seedling roots in the tropical forest on Barro Colorado Island (BCI), Republic of Panama. In the first year, we sampled newly emergent seedlings of the understory treelet Faramea occidentalis and the canopy emergent Tetragastris panamensis, from mixed seedling carpets at each of two sites. The following year we sampled surviving seedlings from these cohorts. The roots of 48 plants were analysed using AM fungal-specific primers to amplify and clone partial small subunit (SSU) ribosomal RNA gene sequences. Over 1300 clones were screened for random fragment length polymorphism (RFLP) variation and 7% of these were sequenced. Compared with AM fungal communities sampled from temperate habitats using the same method, the overall diversity was high, with a total of 30 AM fungal types identified. Seventeen of these types have not been recorded previously, with the remainder being similar to types reported from temperate habitats. The tropical mycorrhizal population showed significant spatial heterogeneity and nonrandom associations with the different hosts. Moreover there was a strong shift in the mycorrhizal communities over time. AM fungal types that were dominant in the newly germinated seedlings were almost entirely replaced by previously rare types in the surviving seedlings the following year. The high diversity and huge variation detected across time points, sites and hosts, implies that the AM fungal types are ecologically distinct and thus may have the potential to influence recruitment and host composition in tropical forests. [source]


Host specificity and incidence of Trypanosoma in some African rainforest birds: a molecular approach

MOLECULAR ECOLOGY, Issue 9 2001
Ravinder N. M. Sehgal
Abstract Studies of host,parasite interactions in birds have contributed greatly to our understanding of the evolution and ecology of disease. Here we employ molecular techniques to determine the incidence and study the host-specificity of parasitic trypanosomes in the African avifauna. We developed a polymerase chain reaction (PCR)-based diagnostic test that amplified the small subunit ribosomal RNA gene (SSU rRNA) of Trypanosoma from avian blood samples. This nested PCR assay complements and corroborates information obtained by the traditional method of blood smear analysis. The test was used to describe the incidence of trypanosomes in 479 host individuals representing 71 rainforest bird species from Cameroon, the Ivory Coast and Equatorial Guinea. Forty-two (59%) of these potential host species harboured trypanosomes and 189 individuals (35%) were infected. To examine host and geographical specificity, we examined the morphology and sequenced a portion of the SSU rRNA gene from representative trypanosomes drawn from different hosts and collecting locations. In traditional blood smear analyses we identified two trypanosome morphospecies, T. avium and T. everetti. Our molecular and morphological results were congruent in that these two morphospecies had highly divergent SSU rRNA sequences, but the molecular assay also identified cryptic variation in T. avium, in which we found seven closely allied haplotypes. The pattern of sequence diversity within T. avium provides evidence for widespread trypanosome mixing across avian host taxa and across geographical locations. For example, T. avium lineages with identical haplotypes infected birds from different families, whereas single host species were infected by T. avium lineages with different haplotypes. Furthermore, some conspecific hosts from geographically distant sampling locations were infected with the same trypanosome lineage, but other individuals from those locations harboured different trypanosome lineages. This apparent lack of host or geographical specificity may have important consequences for the evolutionary and ecological interactions between parasitic trypanosomes and their avian hosts. [source]


DNA barcodes to identify species and explore diversity in the Adelgidae (Insecta: Hemiptera: Aphidoidea)

MOLECULAR ECOLOGY RESOURCES, Issue 2009
R. G. FOOTTIT
Abstract The Adelgidae are relatively small, cryptic insects, exhibiting complex life cycles with parthenogenetic reproduction. Due to these characteristics, the taxonomy of the group is problematic. Here, we test the effectiveness of the standard 658-bp barcode fragment from the 5,-end of the mitochondrial cytochrome c oxidase 1 gene (COI) in differentiating among 17 species of Adelgidae, in associating life-cycle stages, and in assessing patterns of geographical variation in selected species. Species of Adelgidae are well-differentiated by DNA barcodes, enabling the identification of different morphological forms, immature stages and individuals on different hosts and at different periods of the life cycle. DNA barcodes have uncovered cryptic diversity within taxa and, in other cases, a lack of sequence divergence in species pairs previously separated by life-cycle characteristics, indicating a need for further taxonomic analysis. [source]


Programmed responses to virus replication in plants

MOLECULAR PLANT PATHOLOGY, Issue 1 2000
A. J. Maule
Despite their economic importance, we understand very little about the mechanism leading to symptom formation in compatible virus infections. By applying a spatial analysis to advancing infection fronts, we have been able to relate molecular events in small groups of cells to a sequence of virus-induced changes. This sequence starts ahead of the main front of virus replication and virus protein accumulation and lasts beyond the time at which virus replication has ceased. The host changes include alterations in gene expression, physiology and cellular ultrastructure. The relationship between these effects has been analysed in comparative studies between different virus infections in different hosts and abiotic stress. The research points to there being common features for different viruses leading to common effects. Also, although many of the consequences of virus infection are similar to the effects of heat shock, there are sufficient differences to suggest that the two inducers use distinct control pathways. The immediate challenge for the future is to establish synchronous infections of tissues so that the complex relationship between the virus and the host can be investigated using temporal rather than spatial analyses. [source]


Distinct host-related dendritic cell responses during the early stage of Plasmodium yoelii infection in susceptible and resistant mice

PARASITE IMMUNOLOGY, Issue 5 2010
W. ZHENG
Summary The diverse outcomes of experimental murine infection with Plasmodium parasites, ranging from spontaneous cure to death, depend largely on the establishment of an effective Th1 immune response during the early stages of infection. However, the molecular and cellular factors responsible for the induction and regulation of this response are poorly understood. As immunity is initiated by dendritic cells (DCs), we compared their phenotype and function during the early stages of infection with Plasmodium yoelii 17XL (P.y 17XL) strain in susceptible (BALB/c) and resistant (DBA/2) mice. Resistant DBA/2 mice developed a greater number of myeloid (CD11c+CD11b+) and mature DCs, which were fully functional and capable of secreting IL-12p40. In contrast, susceptible BALB/c mice produced more plasmacytoid (CD11c+CD45R/B220+) and less mature DCs, resulting in high levels of IL-10 and TGF-,1. In addition, an in vitro experiment confirmed that splenic DCs from the two strains of mice differ in their ability to prime CD4+T cells in response to P.y 17XL stimulation. These findings indicate that the subset, the phenotype and the type of inflammatory and anti-inflammatory signals of splenic DCs are critical factors responsible for the discrepancy in the ability to induce or regulate Th1 immune responses in different hosts. [source]


Selectivity of pesticides used on cotton (Gossypium hirsutum) to Trichogramma pretiosum reared on two laboratory-reared hosts,

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 1 2006
Cristina S Bastos
Abstract The side-effects of pesticides (insecticides, fungicides, herbicides and plant growth regulators) used on cotton were tested on adults and pupae of Trichogramma pretiosum Riley reared in the laboratory on two different hosts, the Angoumois grain moth (Sitotroga cerealella Olivier) and the Mediterranean flour moth (Ephestia kuehniella (Zeller)). The eggs of the host enclosing the parasitoid pupae received direct pesticide sprays, while the adults of the parasitoid were exposed to the pesticides through contact with residues on sprayed eggs offered to parasitism. Alpha-cypermethrin, carbosulfan, deltamethrin, endosulfan, profenofos and zeta-cypermethrin were highly noxious to the parasitoid, significantly reducing the percentage of emergence and parasitism of T. pretiosum developing in E. kuehniella or S. cerealella eggs. However, the pupal stage of the parasitoid developing in S. cerealella eggs was less susceptible to alpha-cypermethrin and deltamethrin. Lufenuron and metamidophos greatly reduced the percentage of adult emergence from eggs of both hosts, while novaluron only interfered on this variable when the wasps were developing in E. kuehniella eggs. However, lufenuron and monocrotophos had no effect on the parasitoid pupae of T. pretiosum developing in E. kuehniella eggs. Chlorfluazuron, diafenthiuron, diflubenzuron, fentin hydroxide, mepiquat chloride, novaluron, thiacloprid and triflumuron did not affect T. pretiosum emergence when eggs of S. cerealella enclosing pupae of the wasps were surface treated. The pesticides azoxystrobin, carbendazin + thiram, mepiquat chloride and novaluron had no effect on the ability of the wasps to parasitise E. kuehniella eggs. However, only mepiquat chloride did not affect the percentage of F1 wasps emerging from E. kuehniella eggs. The remaining pesticides moderately reduced the percentage of emergence and parasitism of the wasps when they had contact with the chemicals during their pupal or adult stage. Thus there were differences in pesticide toxicity according to the host used for parasitoid development. These differences were hypothesised to occur because of differences in egg morphology and parasitoid performance. Copyright © 2005 Society of Chemical Industry [source]


Compatible and Incompetent Paxillus involutus Isolates for Ectomycorrhiza Formation in vitro with Poplar (Populus×canescens) Differ in H2O2 Production

PLANT BIOLOGY, Issue 1 2004
A. Gafur
Abstract: Isolates of Paxillus involutus (Batsch) Fr. collected from different hosts and environmental conditions were screened for their ability to form ectomycorrhizal symbiosis with hybrid poplar P.×canescens (= Populus tremula L. ×P. alba) in vitro. The ability to form ectomycorrhiza varied between the fungal isolates and was not correlated with the growth rate of the fungi on agar-based medium. The isolate MAJ, which was capable of mycorrhiza synthesis under axenic conditions, and the incompetent isolate NAU were characterized morphologically and anatomically. MAJ formed a typical hyphal mantle and a Hartig net, whereas NAU was not able to penetrate the host cell walls and caused thickenings of the outer cell walls of the host. MAJ, but not NAU, displayed strong H2O2 accumulation in the outer hyphal mantle. Increases in H2O2 in the outer epidermal walls and adjacent hyphae of the incompetent isolate were moderate. No increases of H2O2 in response to the mycobionts were found inside roots. Suggested functions of H2O2 production in the outer hyphal mantle of the compatible interaction are: growth regulation of the host's roots, defence against other invading microbes, or increasing plant-innate immunity. The system established here for P.×canescens compatible and incompetent fungal associations will be useful to take advantage of genomic information now available for poplar to study tree-fungal interactions at the molecular and physiological level. [source]


Different forms of interference between two tobamoviruses in two different hosts

PLANT PATHOLOGY, Issue 6 2000
I Aguilar
Oilseed rape mosaic (ORMV) and tobacco mild green mosaic (TMGMV) tobamoviruses interfered with each other when infecting the same host, and interference was host-dependent. In tobacco cross-protection was obtained in two ways: the protecting virus prevented the accumulation of the challenging virus, even in the inoculated leaf; in Arabidopsis, protection was obtained only when the protecting virus was TMGMV. The protecting mechanism in Arabidopsis appeared to differ from that operating in tobacco. Although ORMV could be detected in the inoculated leaf, TMGMV prevented systemic infection by ORMV. Thus the host appears to play an important role in this type of cross-protection. [source]


Identification of the adherent microbiota on the gills and skin of poly-cultured gibel carp (Carassius auratus gibelio) and bluntnose black bream (Megalobrama amblycephala Yih)

AQUACULTURE RESEARCH, Issue 9 2010
Wenwen Wang
Abstract PCR-denaturing gradient gel electrophoresis (DGGE) was applied to analyse the microbial community attached to the gills and skin of poly-cultured gibel carp (Carassius auratus gibelio) and bluntnose black bream (Megalobrama amblycephala Yih) and compare these results with those detected in the rearing water. The microbiota discussed included bacteria, fungi and a specific bacterial taxa of actinomycetes was also analysed. Proteobacteria, Firmicutes, Actinobacteria, Cyanobacteria, Ascomycota, Basidiomycota and some unclassified microbiota were identified. Based on our results, we concluded that: (1) the adherent bacterial/fungal communities on the gills and skin were different from those in the rearing water, (2) the bacterial/fungal diversities on fish gills were lower than that on fish skin, (3) the adherent bacterial/fungal communities on gill and skin of gibel carp were different from that of bluntnose black bream and (4) the adherent actinomycetal community showed certain similarity between the skin of different hosts. Based on our conclusions, we suggested that the topic investigated in the present study merits further investigations. [source]


Thermodynamic Analysis of Receptors Based on Guanidinium/Boronic Acid Groups for the Complexation of Carboxylates, ,-Hydroxycarboxylates, and Diols: Driving Force for Binding and Cooperativity

CHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2004
Sheryl L. Wiskur Dr.
Abstract The thermodynamics of guanidinium and boronic acid interactions with carboxylates, ,-hydroxycarboxylates, and diols were studied by determination of the binding constants of a variety of different guests to four different hosts (7,10). Each host contains a different combination of guanidinium groups and boronic acids. The guests included molecules with carboxylate and/or diol moieties, such as citrate, tartrate, and fructose, among others. The Gibbs free energies of binding were determined by UV/Vis absorption spectroscopy, by use of indicator displacement assays. The receptor based on three guanidinium groups (7) was selective for the tricarboxylate guest. The receptors that incorporated boronic acids (8,10) had higher affinities for guests that included ,-hydroxycarboxylate and catechol moieties over guests containing only carboxylates or alkanediols. Isothermal titration calorimetry revealed the enthalpic and entropic contributions to the Gibbs free energies of binding. The binding of citrate and tartrate was investigated with hosts 7,10, for which all the binding events were exothermic, with positive entropy. Because of the selectivity of hosts 8,10, a simple boronic acid (14) was also investigated and determined to be selective for ,-hydroxycarboxylates and catechols over amino acids and alkanediols. Further, the cooperativity of 8 and 9 in binding tartrate was also investigated, revealing little or no cooperativity with 8, but negative cooperativity with 9. A linear entropy/enthalpy compensation relationship for all the hosts 7,10, 14, and the carboxylate-/diol-containing guests was also obtained. This relationship indicates that increasing enthalpy of binding is offset by similar losses in entropy for molecular recognition involving guanidinium and boronic acid groups. [source]