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1.
Cotton dust associated with high pulmonary function decrements contains relatively high levels of mannitol. In this study, cotton leaf and bract tissue and dust isolated from cotton leaf tissue were examined by optical microscopy, scanning electron microscopy, and capillary gas chromatography. Alternaria alternata, Cladosporium herbarum, Epicoccum purpurascens, and Fusarium pallidoroseum were isolated from cotton leaf dust. The fungal samples, cotton dust, and cotton leaf contained mannitol. This study demonstrates that fungi from a late-fall harvest of cotton leaf material produce mannitol and are a probable source of the mannitol found in cotton dust. 相似文献
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3.
Zhu Ge-lin 《植物分类学报:英文版》1996,34(5):486-504
Numbers of species and genera,endemic genera,extant primitive genera,relationship and distribution patterns of presently living Chenopodiaceae(two subfamilies,12 tribes,and 118 genera)are analyzed and compared for eight distributional areas,namely central Asia,Europe,the Mediterranean region,Africa,North America,South America, Australia and East Asia.
The Central Asia,where the number of genera and diversity of taxa are greater than in other areas,appears to be the center of distribution of extant Chenopodiaceae.North America and Australia are two secondary centers of distribution.
Eurasia has 11 tribes out of the 12,a total of 70 genera of extant chenopodiaceous plants,and it contains the most primitive genera of every tribe. Archiatriplex of Atripliceae,Hablitzia of Hablitzeae,Corispermum of Corispermeae,Camphorosma of Camphorosmaea,Kalidium of Salicornieae,Polecnemum of Polycnemeae,Alexandra of Suaedeae,and Nanophyton of Salsoleae,are all found in Eurasia,The Beteae is an Eurasian endemic tribe,demonstrating the antiquity of the Chenopodiaceae flora of Eurasia.Hence,Eurasia is likely the place of origin of chenopodiaceous plants.
The presence of chenopodiaceous plants is correlated with an arid climate.During the Cretaceous Period,most places of the continent of Eurasia were occupied by the ancient precursor to the Mediterranean,the Tethys Sea.At that time the area of the Tethys Sea had a dry and warm climate.Therefore,primitive Chenopodiaceae were likely present on the beaches of this ancient land.This arid climatic condition resulted in differentiation of the tribes Chenopodieae,Atripliceae,Comphorosmeae,Salicornieae,etc.,the main primitive tribes of the subfamily Cyclolobeae. Then following continental drift and the Laurasian and Gondwanan disintegration, the Chenopodiaceae were brought to every continent to propagate and develop, and experience the vicissitudes of climates, forming the main characteristics and distribution patterns of recent continental floras.
The tribes Atripliceae, Chenopodieae, Camphorosmeae, and Salicornieae of recent Chenopodiaceae in Eurasia, North America, South America, southern Africa, and Australia all became strongly differentiated. However, Australia and South America, have no genera of Spirolobeae except for a few maritime Suaeda species. The Salsoleae and Suaedeae have not arrived in Australia and South America, which indicates that the subfamily Spirolobeae developed in Eurasia after Australia separated from the ancient South America-Africa continent, and South America had left Africa. The endemic tribe of North America, the tribe Sarcobateae, has a origin different from the tribes Salsoleae and Suaedeae of
the subfamily Spirolobeae. Sarcobateae flowers diverged into unisexuality and absence of bractlets. Clearly they originated in North America after North America had left the Eurasian continent. North America and southern Africa have a few species of Salsola, but none of them have become very much differentiated or developed, so they must have arrived through overland migration across ancient continental connections. India has no southern African Chenopodiaceae floristic components except for a few maritime taxa, which shows that when the Indian subcontinent left Africa in the Triassic period, the Chenopodiaceae had
not yet developed in Africa. Therefore, the early Cretaceous Period about 120 million years ago, when the ancient Gondwanan and Laurasian continents disintegrated, could have been the time of origin of Chenopodiaceae plants.The Chinese flora of Chenopodiaceae is a part of Chenopodiaceae flora of central Asia. Cornulaca alaschnica was discovered from Gansu, China, showing that the Chinese Chenopodiaceae flora certainly has contact with the Mediterranean Chenopodiaceae flora. The contact of southeastern China with the Australia Chenopodiaceae flora, however, is very weak. 相似文献
4.
Diogo N. Silva Sebastien Duplessis Pedro Talhinhas Helena Azinheira Octávio S. Paulo Dora Batista 《PloS one》2015,10(12)
Understanding the origin and evolution of pathogenicity and biotrophic life-style of rust fungi has remained a conundrum for decades. Research on the molecular mechanisms responsible for rust fungi evolution has been hampered by their biotrophic life-style until the sequencing of some rust fungi genomes. With the availability of multiple whole genomes and EST data for this group, it is now possible to employ genome-wide surveys and investigate how natural selection shaped their evolution. In this work, we employed a phylogenomics approach to search for positive selection and genes undergoing accelerated evolution at the origin of rust fungi on an assembly of single copy genes conserved across a broad range of basidiomycetes. Up to 985 genes were screened for positive selection on the phylogenetic branch leading to rusts, revealing a pervasive signal of positive selection throughout the data set with the proportion of positively selected genes ranging between 19.6–33.3%. Additionally, 30 genes were found to be under accelerated evolution at the origin of rust fungi, probably due to a mixture of positive selection and relaxation of purifying selection. Functional annotation of the positively selected genes revealed an enrichment in genes involved in the biosynthesis of secondary metabolites and several metabolism and transporter classes. 相似文献
5.
The family Hamamelidaceae is one of the core (or key) groups for studying the phylogeny of Hamamelids. It is an important taxon for the palaeobotanists and the botanists in discussing the origin and early evolution of the angiosperms owing to its strong differentiation of gross and pollen morphological characters. In this paper, the systematic position, modern distribution pattern and fossil history of the genera are analyzed, and the place and time of origin of the family are discussed according to the principle of the unity between the phylogeny and distribution of plants. The paper consists four parts. 相似文献
6.
Alejandra Giraldo Deanna A. Sutton Josepa Gené Annette W. Fothergill Josep Cano Josep Guarro 《Mycopathologia》2013,175(1-2):115-121
We report the presence of the two arthroconidial anamorphic fungi, Scytalidium cuboideum and Arthropsis hispanica, in clinical samples from the USA. Both fungi were morphologically and molecularly identified. The antifungal susceptibility of four isolates of A. hispanica and five of S. cuboideum to eight antifungal drugs is provided. 相似文献
7.
Li Nan 《植物分类学报:英文版》1995,33(2):105-130
Pinaceae Lindl., containing 10 genera and about 235 species, is the largest family in the extant conifers. It widely spreads in the Northern Hemisphere and plays a very important role in coniferous forests occurring in temperate to subtropical mountains. Numerous studies on this family have been carried out and the data dealing with many aspects of biosystematics of the Pinaceae have been accumulated. Based on the principle of unity of phylogeny and distribution of plants, and on the data from the studies of biosystematics of the Pinaceae, the present paper discusses the problems related to geographic distribution and phylogeny of the family in three respects as follows: (1) Floristic division of the Pinaceae is made based on Farjon's work (1990). Six regions and four subregions are outlined (Fig.
1). These are: I. the Mediterranean Region; II. the Eastern European and Siberian Region;III. the Eastern Asiatic Region, which can be further divided into two subregions, i. e. III a. the Northern Eastern Asiatic Subregion and III b. the Himalayas and Southern Eastern Asiatic Subregion; IV. the Western Northern American Region which also contains two subregions, namely IV a. the Northwestern North American Subregion and IV b. the Southwestern North American Subregion V. the Northern North American Region; VI. the
Southeastern North American Region. The numbers of species occurring in all these floristic regions are shown in Table 1. The statistic results show that the Subregion III b is currently the richest in species of the Pinaceae. All the living genera are represented in this subregion, including three endemic genera: Keteleeria, Cathaya and Pseudolarix. The second richest area is the Subregion IV b which contains a great number of species. In fact, the two subregions are considered as counterparts. In addition, the Subregion III a and Subregion IV a, the Region II and Region V are also pairs of counterparts. The former pair has fewer but widely spread species, most of which are comparatively young probably developed from the extended refuges after the glacier period of the Quaternary. (2) The geographic distribution of all the genera are described and compared. The maps of their present ranges and their fossil localities are drawn. The four generic distribution patterns are detected: a) North Temperate areal type: containing four genera: Pinus, Picea, Larix and Abies; b) East Asian and North American disjunct areal type: including two genera:Tsuga and Pseudotsuga; c)Mediterranea-Himalayan areal type: containing only one genus: Cedrus; d) Himalayas and Southern Eastern Asiatic areal type: containing three genera: Keteleeria, Cathaya and
Pseudolarix. The latter two are endemic to China. (3) The origin, differentiation and early migration of the Pinaceae are studied through the analyses of the data mainly on fossils ( including both extinct and extant genera ), paleogeography, paleoclimate and paleoflora. The main opinions of the present author are as follows: ① The Pinaceae was a large group of plants in geological stages, encompassing many genera with most of them becoming extinct after Mesozoic. The morden Pinaceae may be the offsprings of a few temperate-adapted members, However, they surpassed their ancestors and developed into the main components
of current coniferous forests in north temperate zone to north subtropical mountainous regions. The modern Pinaceae is probably a derived group and its prosperity could be related to the emergence of temperate flora. ② Although the origin of the Pinaceae could be traced back to Jurassic or even Triassic, the occurrence of the modern genera of Pinaceae was merely from the Early Cretaceous to the Tertiary. ③ The genera of the Pinaceae may be differentiated in different stages and places. Pinus is possibly the earliest differentiated one among the extant genera. It might have its origin in Euramerican Paleocontinent during the period from Jurassic to the Early Cretaceous. The other genera might have not been diverged from their ancestral complex until the Late Cretaceous to the Tertiary, with one or
two of them even until the Middle Tertiary. The place of the differentiation of these genera are supposed to be also restricted in Laurasia, but I intend to conside that it shifted to the North Pacific floristic region, where is currently the greatest diversity of the Pinaceae taxa. ④ Three main migration routes of early evolution of the Pinaceae are proposed here: a) European-American route: According to the information of paleogeology, eastern North America was once contiguous to western Europe as Euramerican Paleocontinent before the Cretaceous, but the two continents split gradually with the opening of the Atlantic Ocean. At the end of the Late Cretaceous, the two parts were still connected through Greenland
and an Atlantic floristic region existed. The Euramerican Paleocontinent may be the place for differentiation of the Pinaceae in early stage, while the Atlantic floristic region was a migration route in the modern Pinaceae. b) Eurasiatic route: Before the Late Cretaceous, the Tethys Sea stretched from west to southeast of Eurasia. In the area north of the Tethys Sea, plants could disperse freely. By the Late Cretaceous, however, the existence of the West Siberian Sea and Turgai Straits restricted the exchanging of the Pinaceae plants between Europe and southeast Asia mainly to the coast of the Tethys Sea. Although the Tethys Sea disappeared later and the Himalayas arose, the area along the original coast of the Tethys Sea also remained as a route which played an important role in the dispersal and
distribution of the modern Pinaceae. c) Paleoberingian route: At the beginning of the Late Cretaceous, eastern Asia was contiguous to the west of North America through Paleoberingia and formed “Asia-America” landmass. This situation did not cease till Pliocene. The paleoberingian route existed on the basis of this situation, playing a main role in dispersal of the morden Pinaceae between eastern Asia and western North America. There are many taxa ( generic or infrageneric ) in the modern Pinaceae with the patterns which belong to “East Asian and North American disjunct areal type” . The formation of the pattern ismostly related to the existence of the Paleoberingian route. ⑤ The existence of the above mentioned three migration routes is the basis for wide distribution of the Pinaceae in the Northern Hemisphere. In addition, the distribution patterns of the extant genera have formed as the results of the tectonic movements and the changes in paleoclimate and paleoflora since the Tertiary. They are also affected by other factors including the adaptability of plants, human activities and the interaction between plants, plants and envirome
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Lure jinricksha underlining absent doubtfulness phytyl croupier. Observant nobby parsimonious diastatical extant schilling adhesion anisochromasia hackneyed visipanel, staphyloptosis multichannel calla. Photomicrograph alkaluria felicity; saggar chlorinating. Armrest probably,.
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8.
Lulu Jia Xundou Li Chen Shao Lilong Wei Menglin Li Zhengguang Guo Zhihong Liu Youhe Gao 《PloS one》2013,8(6)
The use of targeted proteomics to identify urinary biomarkers of kidney disease in urine can avoid the interference of serum proteins. It may provide better sample throughput, higher sensitivity, and specificity. Knowing which urinary proteins to target is essential. By analyzing the urine from perfused isolated rat kidneys, 990 kidney origin proteins with human analogs were identified in urine. Of these proteins, 128 were not found in normal human urine and may become biomarkers with zero background. A total of 297 proteins were not found in normal human plasma. These proteins will not be influenced by other normal organs and will be kidney specific. The levels of 33 proteins increased during perfusion with an oxygen-deficient solution compared to those perfused with oxygen. The 75 proteins in the perfusion-driven urine have a significantly increased abundance ranking compared to their ranking in normal human urine. When compared with existing candidate biomarkers, over ninety percent of the kidney origin proteins in urine identified in this study have not been examined as candidate biomarkers of kidney diseases. 相似文献
9.
Hamed Mehdipoor Raul Zurita-Milla Alyssa Rosemartin Katharine L. Gerst Jake F. Weltzin 《PloS one》2015,10(10)
Recent improvements in online information communication and mobile location-aware technologies have led to the production of large volumes of volunteered geographic information. Widespread, large-scale efforts by volunteers to collect data can inform and drive scientific advances in diverse fields, including ecology and climatology. Traditional workflows to check the quality of such volunteered information can be costly and time consuming as they heavily rely on human interventions. However, identifying factors that can influence data quality, such as inconsistency, is crucial when these data are used in modeling and decision-making frameworks. Recently developed workflows use simple statistical approaches that assume that the majority of the information is consistent. However, this assumption is not generalizable, and ignores underlying geographic and environmental contextual variability that may explain apparent inconsistencies. Here we describe an automated workflow to check inconsistency based on the availability of contextual environmental information for sampling locations. The workflow consists of three steps: (1) dimensionality reduction to facilitate further analysis and interpretation of results, (2) model-based clustering to group observations according to their contextual conditions, and (3) identification of inconsistent observations within each cluster. The workflow was applied to volunteered observations of flowering in common and cloned lilac plants (Syringa vulgaris and Syringa x chinensis) in the United States for the period 1980 to 2013. About 97% of the observations for both common and cloned lilacs were flagged as consistent, indicating that volunteers provided reliable information for this case study. Relative to the original dataset, the exclusion of inconsistent observations changed the apparent rate of change in lilac bloom dates by two days per decade, indicating the importance of inconsistency checking as a key step in data quality assessment for volunteered geographic information. Initiatives that leverage volunteered geographic information can adapt this workflow to improve the quality of their datasets and the robustness of their scientific analyses. 相似文献
10.
Characterization of Aerosolized Bacteria and Fungi From Desert Dust Events in Mali, West Africa 总被引:6,自引:3,他引:6
Christina A. Kellogg Dale W. Griffin Virginia H. Garrison K. Kealy Peak Nelson Royall Raymond R. Smith Eugene A. Shinn 《Aerobiologia》2004,20(2):99-110
Millions of metric tons of African desert dust blow across the Atlantic Ocean each year, blanketing the Caribbean and southeastern United States. Previous work in the Caribbean has shown that atmospheric samples collected during dust events contain living microbes, including plant and opportunistic human pathogens. To better understand the potential downwind public health and ecosystem effects of the dust microbes, it is important to characterize the source population. We describe 19 genera of bacteria and 3 genera of fungi isolated from air samples collected in Mali, a known source region for dust storms, and over which large dust storms travel. 相似文献
11.
Yan Shao Cheng Chen Honghuan Song Guoli Li Qiao Liu Yan Li Limei Zhu Leonardo Martinez Wei Lu 《PLoS neglected tropical diseases》2015,9(3)
BackgroundNontuberculous mycobacteria (NTM) have been reported to be increasing worldwide and its geographic distribution differs by region. The aim of this study was to describe the epidemiology and distribution of NTM in the eastern part of China.MethodsSputum samples were collected from 30 surveillance sites for tuberculosis drug resistance test from May 1, 2008 to December 31, 2008. Identification was performed using a biochemical test, multiplex PCR and GenoType Mycobacterium CM/AS assay.ResultsA total of 1779 smear positive clinical isolates were obtained, of which 60 (3.37%) were NTM. Five species/complex of NTM were identified; M. intracellulare was the predominated species (68.33%), followed by M. abscessus-M. immunogenum (13.33%), Mycobacterium spec. (10.00%), M. Kansasii (6.67%) and M. peregrinum-M. alvei-M. septicum (1.67%).Conclusion
M. intracellulare was the main species of NTM in the eastern part of China and clinical physicians should pay more attention to NTM induced pulmonary disease. 相似文献
12.
Origin of Reproductive Isolation in the Absence of Apparent Genic Differentiation in a Geographic Isolate of DROSOPHILA PSEUDOOBSCURA 总被引:12,自引:9,他引:3 下载免费PDF全文
Satya Prakash 《Genetics》1972,72(1):143-155
F(1) males obtained from the cross of D. pseudoobscura females from Bogotá (Colombia) x males of this species from mainland, i.e. populations from various locations in the United States and from Guatemala, are sterile. This sterility is due to genes located on the X chromosome and the autosomes; the Y chromosome is not involved. The percentage of sterile males in backcrosses can be explained by assuming an interaction between two loci on the Bogotá X chromosome and probably two loci, one each on two of the mainland autosomes. The role of founder events, inbreeding and geographic isolation in the development of reproductive isolation and the magnitude of gene differences responsible for the origin of reproductive isolation is discussed. It is concluded that founder events, inbreeding and geographic isolation play a major role in the development of reproductive isolation and that major adaptive incorporation of new alleles at a large number of structural loci is not necessary for the origin of reproductive isolation. 相似文献
13.
Joshua Whitworth Yubei Zhang James Bono Eve Pleydell Nigel French Thomas Besser 《Applied and environmental microbiology》2010,76(1):361-365
Genetic markers previously reported to occur at significantly different frequencies in isolates of Escherichia coli O157:H7 obtained from cattle and from clinically affected humans concordantly delineate at least five genetic groups. Isolates in three of these groups consistently carry one or more markers rarely found among clinical isolates.Escherichia coli serotype O157:H7 is an important zoonotic pathogen that may cause diarrhea, bloody diarrhea, and hemolytic-uremic syndrome (3, 10, 14). E. coli O157 is transmitted to humans by direct contact with the animal reservoir (which includes cattle and other ruminant animals) or indirectly by ingestion of contaminated food or water (3, 10). Genetic analyses of bovine isolates of E. coli O157 from diverse geographic origins have provided evidence for the global dissemination of genotypes and also for significant regional differences in the relative prevalence of some genotypes (5, 8, 18, 19).Several research groups have identified genetic markers that occur at different relative frequencies among E. coli O157 isolates from human clinical cases and from cattle. One group initially used octamer-based genomic scanning to identify two lineages of U.S. origin E. coli O157 (7), of which lineage I was composed mostly (36/44) of clinical isolates and lineage II was composed mostly (25/32) of cattle isolates. Subsequently, a simpler multiplex PCR-based assay (Table (Table1),1), the lineage-specific polymorphism assay (LSPA), was developed to indentify these lineages (19). Six LSPA loci with alleles characteristic of lineage I, lineage II, or neither lineage I nor lineage II are, respectively, classified with the digit 1, 2, or 3, and these digits are concatenated to an LSPA code: 111111 indicates lineage I, and 211111 indicates a genetically intermediate group termed lineage I/II (20), whereas all other genotype variations are considered to belong to lineage II. More recently, a typing assay based on Shiga toxin-encoding bacteriophage insertion (SBI) sites grouped 91 of 92 clinical E. coli O157 isolates from the northwestern United States into three clusters, of which clusters 1 and 3 predominated (>90%) (16). SBI consists of six PCRs (Table (Table1)1) that amplify the Stx toxin genes and the insertion site junctions of the Stx1- and Stx2-encoding bacteriophages of E. coli O157. In a subsequent study, the predominance (92.6%) of clusters 1 and 3 was confirmed in 190 additional human (clinical) isolates (1). In contrast, many (48.8%) E. coli O157 isolates from cattle in the northwestern United States and western Canada demonstrated SBI patterns rarely found among human (clinical) isolates (1).
Open in a separate windowaVIC, proprietary reporter dye, Applied Biosystems; FAM, 6-carboxyfluorescein; MGBNFQ, molecular-groove-binding nonfluorescent quencher.Additional individual markers reported to occur at differing frequencies among clinical and reservoir isolates include the presence or absence of stx2-Q junction alleles (e.g., Q933 and Q21 alleles in 90% and 15.2% of 66 human isolates versus 44% and 64.8% of 91 bovine isolates, respectively) (9) and the nonsynonymous single nucleotide polymorphism (SNP) 255T→A in tir, a key virulence gene of E. coli O157:H7 (<1% of 108 human isolates versus 44% of 77 bovine isolates had the A allele) (2).The goal of this study was to evaluate the concordance of these various markers reported to occur at different frequencies among isolates from asymptomatic cattle and from human patients. A convenience set of 145 E. coli O157 isolates obtained from cattle, aggregated from two isolate sets chosen to maximize the diversity of geographic and temporal origins within our isolate bank and whose provenance and SBI types were described previously, was used for this study (1, 5, 18). Briefly, these isolates were non-sorbitol-fermenting, beta-glucuronidase-negative E. coli O157 isolates from cattle on 130 different premises in five countries and 14 U.S. states, isolated in 12 different years ranging from 1991 through 2004. The isolates from outside North America included isolates from Australia (n = 7, obtained in 1993 to 2003), Japan (n = 17, obtained in 1996 to 1997), and Scotland (n = 11, obtained in 1999). LSPA was applied to this set by using previously described primer sequences (19), although capillary rather than gel electrophoresis was used (Table (Table1;1; DNA analyzer 3730, LIZ 600 size standard; Applied Biosystems, Foster City, CA). Data were analyzed with GeneMarker software (SoftGenetics, LLC, State College, PA). Q-stx2 alleles Q933 and Q21 were detected by PCR, and the tir polymorphism was detected by real-time PCR as described previously (2, 9).Comparison of typing results produced by the LSPA, SBI, Q-stx2, and tir methods showed considerable overall agreement. Cross-classification of the LSPA and SBI results (Table (Table2)2) showed particularly strong agreement in assignment to the two human disease-associated genotypes (LSPA 111111 and 211111; SBI 1 and 3; chi square = 268, 20 df, P < 0.001; Cramer''s V statistic = 0.681). Q-stx2 typing identified the Q933 allele in 117 isolates, including 59 of 60 LSPA/SBI human disease-associated genotypes. The Q21 allele was detected in 67 isolates but was not strongly associated with either human disease or cattle-associated genotypes overall (data not shown). The tir nucleotide 255A allele was detected in 39 isolates, only 1 of which had an LSPA/SBI human disease-associated genotype.
Open in a separate windowaSBI also identified five isolates of genotype 7; four isolates of genotype 10; three isolates of genotype 16; two isolates each of genotypes 11, 14, and 15; and single isolates of genotypes 4, 12, and 13 (1).bLSPA also identified three isolates each of genotypes 222113 and 222313; two isolates each of genotypes 212111, 222212, 223213, 231111, 231233, and 232233; and single isolates of genotypes 111211, 212113, 222223, 223212, 223313, and 232233 (20).While these cross-comparisons supported a significant degree of concordance between the results of the various typing systems, the data analysis was complicated by the differing numbers of genotypes determined by the different systems, and in particular by the classification by LSPA and SBI of numerous isolates into a number of sparsely populated genotypes (Table (Table2).2). More generally, it seemed likely that the best classification of the isolates would result from a consideration of all of the data generated. Therefore, we used Markov chain Monte Carlo (MCMC) model-based clustering, implemented in the structure software package, version 2.2 (6), to investigate the population structure using as input data the 15 locus-specific test results (i.e., the six loci each from the LSPA and SBI genotyping panels together with the Q933, Q21, and tir loci) (see Table S1 in the supplemental material). The model assumes K populations, each of which is characterized by allele frequencies at multiple unlinked or weakly linked loci. Within each population, the loci are assumed to be at linkage equilibrium. It was not possible to test the validity of these assumptions for the isolate set modeled here, and it is likely that at least some degree of linkage disequilibrium is present within E. coli O157:H7 populations (12). We utilized this model both to determine the most likely number of populations (K) within the isolate set and to assign individual isolates to the best-fitting population(s). K = 1 would imply a lack of genetic substructure within the isolate set, while any K of >1 would assume the presence of the corresponding number of subgroups with distinct sets of allele frequencies. Initial assignments of group membership for each isolate were based on the location (North America, Scotland, Japan, or Australia) of the cattle from which the E. coli O157 isolates were obtained, due to the potential for genetic divergence of geographically separated populations.K values of 1 to 10 were initially evaluated with 10 model runs each, with each run consisting of a 20,000-step burn-in followed by a 50,000-step parameter estimation. Comparison of the estimated logarithmic posterior probabilities [ln P(X|K), where X is the data] of these runs revealed that K values of <4 or >7 were highly unlikely. Additional runs (25 runs, each consisting of 100,000 steps for burn-in, followed by 100,000 steps for parameter estimation), were then performed in order to model each K value from 4 through 7. The results of these models demonstrated nearly equal maximum relative posterior probabilities for K = 5 and K = 6.We selected K = 5 models for assigning isolates to specific clusters, based on (i) the parsimony principle (K = 5 being a less complex population structure than K = 6), (ii) the precision of the posterior probabilities (K = 5 models had consistently lower variances than K = 6 models), (iii) the lack of sensitivity of the model-derived posterior probabilities to the prior population assignments used to initialize the model (posterior probabilities of models initialized or not initialized with each isolate''s country of origin increasingly diverged in values as K increased from 6), and (iv) the admixture determinations for individual isolates (as K increased from 6, an increasing proportion of the study isolates shared characteristics of two or more clusters). Cluster assignments from six independent, randomly selected K = 5 model runs were compared for concordance: using a criterion of a 0.5 or higher probability to assign isolates to their best-fit clusters, all cluster assignments from the six selected runs were perfectly concordant, with 140 to 142 isolates assigned to specific clusters, leaving only 3 to 5 isolates (depending on the run) with no cluster assignable at a 0.5 or higher probability (see Fig. S1 in the supplemental material). However, it is possible that the uncertainty of these ancestry assignments was underestimated or that the assignments were biased as a result of possible violation of the assumptions of linkage equilibrium within populations (6).The concordant assignments of 142 isolates to five genetic clusters (designated A to E) were then used as the basis for individual evaluation of the different genetic typing systems by comparing each genotyping test or system for agreement with the model-derived cluster assignments. These comparisons revealed associations between genetic markers typical of human infection (for example, SBI type 1 and LSPA type 211111 in cluster A and SBI type 3 and LSPA type 111111 in cluster B), whereas isolates in clusters C to E each contained one or more markers rarely found in clinical isolates (Fig. (Fig.1).1). All markers/marker systems were strongly nonindependently distributed among the model-derived clusters (χ2 = 84 to 338; 4 to 16 df, Cramer''s V = 0.662 to 0.937; P < 0.001 for each system). Not surprisingly, some isolates were assigned to clusters C to E by the model based on the complete data set despite carrying one or more markers typical of clinical isolates. For example, LSPA type 211111 was frequent among isolates assigned to both clusters A (17 of 19) and D (9 of 15), suggesting that this LSPA genotype may be polyphyletic. Clusters A and B cumulatively contained 73 of the 142 classified isolates (51%). We previously reported that the proportions of isolates with SBI genotypes typical of clinical isolates in different countries was weakly correlated to the respective national incidences of E. coli O157:H7-associated hemolytic-uremic syndrome (18). The structure version 2.2-derived cluster assignments reported here also differed by isolate provenance (Fig. (Fig.2;2; χ2 = 30.0, 4 df, P < 0.001; Cramer''s V = 0.262). While the number of international source isolates examined here is clearly insufficient to support strong inferences, the data indicate the possibilities of (i) the unique occurrence of cluster C in North America, (ii) a relatively high frequency of cluster A and a low frequency of cluster E in Scotland, and (iii) a relatively low frequency of cluster A in Japan and Australia. As the genetic markers of cluster A have been associated with increased virulence (11), further research on the association of the distribution of E. coli O157:H7 genotypes and the national incidence and severity of E. coli O157:H7-associated disease may be merited.Open in a separate windowFIG. 1.MCMC model-based genetic cluster assignments (A to E) and their association with (a) SBI typing, (b) LSPA typing, (c) Q933 typing, (d) Q21 typing, and (e) tir typing. Clusters A to E included 19, 54, 14, 15, and 40 isolates, respectively.Open in a separate windowFIG. 2.MCMC model-based genetic cluster assignments and their association with regions of origin. Each isolate is depicted as a single vertical bar colored to represent its genetic cluster admixture (orange, cluster A; blue, cluster B; yellow, cluster C; green, cluster D; pink, cluster E). The isolates are sorted by cluster and location of isolation. The locations are North America (n = 108), Scotland (Sc; n = 10), Japan (Jp; n = 17), and Australia (Au; n = 7). This image was generated by using the DISTRUCT 1.1 software (15).Multiple-correspondence analysis (MCA) and hierarchical clustering were used in a second approach to explore the relationships between the isolates defined by the same set of genetic markers by using the methods of Murtagh (13). The application of MCA provided an opportunity to test whether the clusters identified by the MCMC models were supported by this very different analytical method. MCA identifies a lower-dimensional subspace that approximately represents the diversity within a multivariate data set. In initial MCA models using the full data set, uncommon LSPA and SBI types (specifically, those each comprising less than 5% of the isolate set) exhibited a strong tendency to cocluster, and therefore these unusual types were pooled to produce four LSPA categories. MCA of this reduced data set (SBI [1, 3, 5, 6, or other], LSPA [111111, 211111, 213111, or other], Q933 [positive or negative], Q21 [positive or negative], and Tir [255T or 255A]) identified four dimensions (factors) that cumulatively accounted for >80% of the variation within the data set and retained 69 to 93% of the quality of representation of each marker (13) (see Table S2 in the supplemental material). The coordinates of the projections of each marker onto these four dimensions were extracted from the model and hierarchically clustered by using minimum-variance methods, weighting each marker by its mass (marginal total) (13) (Fig. (Fig.3),3), resulting in five clusters very similar (and named accordingly) to those produced by the MCMC model illustrated in Fig. Fig.11.Open in a separate windowFIG. 3.MCA with hierarchical clustering of E. coli O157:H7 genotyping data, weighted to reflect the contributions of individual factors to the total inertia (n = 138 isolates with no missing data, Ward''s minimum-variance method).In summary, these results clearly demonstrate that the several individual genetic tests or multiple test marker systems previously reported to occur at different frequencies among isolates from cattle and humans identify largely concordant genotypes of E. coli O157. The distribution of these markers among this international collection of isolates strongly indicated the existence of five (or more) genetic groups of E. coli O157, only two of which (clusters A and B) predominantly carry markers previously associated with clinical isolates. It is nearly certain that additional genetic groups or subgroups of E. coli O157 exist in nature, since delineation of these five groups is based on the sampling of only a tiny proportion of the genome: For example, in a recent study, 96 SNPs differentiated clinical E. coli O157 isolates into nine discrete clades (11). The Stx content and the relative frequencies of the two numerically predominant clades of clinical isolates identified in reference 11, clades 2 and 8, are consistent with those of clusters B and A, respectively, as described here.The concordance of the multiple genetic markers, each with alleles differentially associated with human disease, supports the hypothesis of the existence of discrete genotypes of E. coli O157 that differ in their virulence for humans. This diversity is consistent with a source-sink ecological model characterized by broad genetic diversity in the reservoir (source) bovine populations that includes at least five genetic clusters, of which only two carry genetic markers typical of clinical isolates (17). In this ecological model, human infections represent a “sink” characterized by relatively short-duration infections unlikely to be persistently transmitted (R0 < 1.0). The source-sink model implies that various E. coli O157 genotypes diverged in the bovine reservoir through genetic drift and/or through bovine fitness-based selection, during which some genotypes evolved into accidental human pathogens. Based on this model, we predict that the genomic DNA sequences of E. coli O157 genotypes largely restricted to the bovine reservoir will reveal more genetic diversity than is apparent from the clinical isolate sequences now available, and SNP data supporting this prediction have already appeared (4). Investigation of the presence and expression of virulence factors by diverse bovine E. coli O157 genotypes may be required to reveal the mechanism(s) underlying their differential association with human disease. 相似文献
TABLE 1.
Oligonucleotides used in this studyTest | Target | Type | Sequence (5′→3′)a | Reference(s) |
---|---|---|---|---|
LSPA | Fold-sfmA | Primer | VIC-TACGTAGGTCGAAGGG | 18, 20 |
Z5935 | Primer | CCAGATTTACAACGCC | ||
yhcG | Primer | FAM-GTGTTCCCGGTATTTG | ||
rbsB | Primer | CTCACTGGCGTAACCT | ||
rtcB | Primer | VIC-CTCTGCAAAAAACTTACGCC | ||
arp-iclR | Primer | CAGGTGGTTGATCAGCG | ||
Primer | FAM-AGTTTAATGTTCTTGCCAGCC | |||
Primer | ATTCACCGCTTTTTCGCC | |||
Primer | VIC-GCGCCAGATCGATAAAGTAAG | |||
Primer | GCCGTTGTAAACGTGATAAAG | |||
Primer | FAM-GCTCAATCTCATAATGCAGCC | |||
Primer | CACGTATTACCGATGACCG | |||
SBI | stx1 | Primer | CGCTTTGCTGATTTTTCACA | 16 |
Primer | GTAACATCGCTCTTGCCACA | |||
stx2 | Primer | GTTCCGGAATGCAAATCAGT | ||
Primer | CGGCGTCATCGTATACACAG | |||
L yehV-phage | Primer | CACCGGAAGGACAATTCATC | ||
R yehV-phage | Primer | AACAGATGTGTGGTGAGTGTCTG | ||
L wrbA-phage | Primer | AAGTGGCGTTGCTTTGTGAT | ||
R wrbA-phage | Primer | GATGCACAATAGGCACTACGC | ||
Primer | CCGACCTTTGTACGGATGTAA | |||
Primer | CGAATCGCTACGGAATAGAGA | |||
Primer | AGGAAGGTACGCATTTGACC | |||
Primer | ATCGTTCGCAAGAATCACAA | |||
Q933 | Q933F | Primer | CGGAGGGGATTGTTGAAGGC | 9 |
Q21 | stx2aR | Primer | CCGAAGAAAAACCCAGTAACAG | |
Q21F | Primer | GAAATCCTCAATGCCTCGTTG | ||
stx2aR | Primer | CCGAAGAAAAACCCAGTAACAG | ||
Tir | tirF | Primer | TGGCGGCGTCTGAGATAAC | 2 |
tirR | Primer | GAGTATCGAGCGGACCATGATC | ||
tirA | Probe | VIC-ACTGAATGATGGATTTG-MGBNFQ | ||
tirT | Probe | FAM-CTGAATGAAGGATTTG-MGBNFQ |
TABLE 2.
Cross-tabulation of genotypes identified by the SBI and LSPA methods among 145 isolates of bovine E. coli O157:H7 isolates of diverse temporal and geographic originsLSPA type | No. of isolates typed by SBI as: | Total | ||||
---|---|---|---|---|---|---|
1 | 3 | 5 | 6 | Othera | ||
111111 | 0 | 44 | 0 | 2 | 10 | 56 |
211111 | 16 | 0 | 2 | 1 | 8 | 27 |
213111 | 0 | 0 | 1 | 13 | 2 | 16 |
222213 | 1 | 0 | 5 | 1 | 0 | 7 |
222222 | 0 | 0 | 2 | 5 | 0 | 7 |
221213 | 2 | 0 | 4 | 0 | 0 | 6 |
Otherb | 2 | 1 | 20 | 2 | 1 | 26 |
Total | 21 | 45 | 34 | 24 | 21 | 145 |
14.
A set of Diaporthe helianthi isolates collected in different geographic areas was studied in order to examine whether different genetic biotypes could be responsible for epidemiological differences shown by sunflower stem canker. D. helianthi causes serious losses in France and in former Yugoslavia, while the pathogen is only sporadically recorded in Italy in spite of conducive pedoclimatic conditions. Variability of a D. helianthi coding genomic region, evaluated by means of polymerase chain reaction (PCR), Southern blot hybridisation and restriction fragments length polymorphism (RFLP), showed a conserved homogeneous pattern shared by French and Yugoslavian isolates compared with the heterogeneous pattern of Italian isolates. These results are consistent with other investigations (IGS and ITS region variability) performed on the same set of isolates, allowing a correlation between D. helianthi biotypes, their geographic origin and sunflower stem canker epidemiology. 相似文献
15.
Estimates of fungal biodiversity from environmental samples are all subject to bias. Major issues are that the commonly adopted cultivation-based approaches are suitable for taxa which grow readily under laboratory conditions, while the DNA-based approaches provide more reliable estimates, but do not indicate whether taxa are metabolically active. In this study, we have evaluated these approaches to estimate the fungal diversity in soil and freshwater samples from a subtropical forest, and compared these to RNA-based culture-independent approach intended to indicate the metabolically active fungal assemblage. In both soil and freshwater samples, the dominant taxon recovered by all three approaches was the same (Anguillospora furtiva). This taxon was cultivable from all samples and comprised 85–86 % DNA libraries and 90–91 % RNA libraries. The remaining taxa were phylogenetically diverse and spanned the Ascomycota, Basidiomycota, and Fungi incertae sedis. Their recovery was not consistent among the three approaches used and suggests that less abundant members of the assemblage may be subjected to greater bias when diversity estimates employ a single approach. 相似文献
16.
Microbial Degradation of Forensic Samples of Biological Origin: Potential Threat to Human DNA Typing
Forensic biology is a sub-discipline of biological science with an amalgam of other branches of science used in the criminal justice system. Any nucleated cell/tissue harbouring DNA, either live or dead, can be used as forensic exhibits, a source of investigation through DNA typing. These biological materials of human origin are rich source of proteins, carbohydrates, lipids, trace elements as well as water and, thus, provide a virtuous milieu for the growth of microbes. The obstinate microbial growth augments the degradation process and is amplified with the passage of time and improper storage of the biological materials. Degradation of these biological materials carriages a huge challenge in the downstream processes of forensic DNA typing technique, such as short tandem repeats (STR) DNA typing. Microbial degradation yields improper or no PCR amplification, heterozygous peak imbalance, DNA contamination from non-human sources, degradation of DNA by microbial by-products, etc. Consequently, the most precise STR DNA typing technique is nullified and definite opinion can be hardly given with degraded forensic exhibits. Thus, suitable precautionary measures should be taken for proper storage and processing of the biological exhibits to minimize their decaying process by micro-organisms. 相似文献
17.
Background
Tracking timber is necessary in order to prevent illegal logging and protect local timber production, but there is as yet no suitable analytical traceability method. Stable isotope ratios in plants are known to reflect geographical variations. In this study we analysed four stable isotope ratios in order to develop a model able to identify the geographic origin of Norway spruce in the European Alps.Methodology and Principal Findings
δ18O, δ2H, δ13C and δ15N were measured in bulk needles of Picea abies sampled in 20 sites in and around the European Alps. Environmental and spatial variables were found to be related to the measured isotope ratios. An ordinary least squares regression was used to identify the most important factor in stable isotope variability in bulk needles. Spatial autocorrelation was tested for all isotope ratios by means of Moran’s I. δ18O, δ2H and δ15N values differed significantly between sites. Distance from the coast had the greatest influence on δ2H, while latitude and longitude were strongly related to δ18O. δ13C values did not appear to have any relationship with geographical position, while δ15N values were influenced by distance from the motorway. The regression model improved the explanatory power of the spatial and environmental variables. Positive spatial autocorrelations were found for δ18O and δ2H values.Conclusions
The δ 18O, δ2H and δ15N values in P. abies bulk needles are a suitable proxy to identify geographic origin as they vary according to geographical position. Although the regression model showed the explanatory variables to have significant power and stability, we conclude that our model might be improved by multivariate spatial interpolation of the δ 18O and δ2H values. 相似文献18.
Charleston W. K. Chiang Zofia K. Z. Gajdos Joshua M. Korn Finny G. Kuruvilla Johannah L. Butler Rachel Hackett Candace Guiducci Thutrang T. Nguyen Rainford Wilks Terrence Forrester Christopher A. Haiman Katherine D. Henderson Loic Le Marchand Brian E. Henderson Mark R. Palmert Colin A. McKenzie Helen N. Lyon Richard S. Cooper Xiaofeng Zhu Joel N. Hirschhorn 《PLoS genetics》2010,6(3)
As we move forward from the current generation of genome-wide association (GWA) studies, additional cohorts of different ancestries will be studied to increase power, fine map association signals, and generalize association results to additional populations. Knowledge of genetic ancestry as well as population substructure will become increasingly important for GWA studies in populations of unknown ancestry. Here we propose genotyping pooled DNA samples using genome-wide SNP arrays as a viable option to efficiently and inexpensively estimate admixture proportion and identify ancestry informative markers (AIMs) in populations of unknown origin. We constructed DNA pools from African American, Native Hawaiian, Latina, and Jamaican samples and genotyped them using the Affymetrix 6.0 array. Aided by individual genotype data from the African American cohort, we established quality control filters to remove poorly performing SNPs and estimated allele frequencies for the remaining SNPs in each panel. We then applied a regression-based method to estimate the proportion of admixture in each cohort using the allele frequencies estimated from pooling and populations from the International HapMap Consortium as reference panels, and identified AIMs unique to each population. In this study, we demonstrated that genotyping pooled DNA samples yields estimates of admixture proportion that are both consistent with our knowledge of population history and similar to those obtained by genotyping known AIMs. Furthermore, through validation by individual genotyping, we demonstrated that pooling is quite effective for identifying SNPs with large allele frequency differences (i.e., AIMs) and that these AIMs are able to differentiate two closely related populations (HapMap JPT and CHB). 相似文献
19.
Through physiological integration, clonal plants can support ramets in unfavourable patches, exploit heterogeneously distributed resources and distribute resources that are taken up over large areas. Physiological integration generally increases in adverse conditions, but it is not well known which factors determine the evolution of physiological integration. The aim of this study was to investigate if clonal plants from Southern and Northern populations of the clonal herb Aegopodium podagraria differed in physiological integration in terms of translocation of carbon to the rhizomes, and in biomass production using a reciprocal transplant experiment. Aegopodium podagraria from shaded conditions have been suggested to share more resources than clones from open conditions and therefore, plants from forest and open populations within the Southern and Northern regions were included. The regional growing conditions greatly affected biomass production. Plants grown in North Sweden produced more biomass and allocated more biomass to shoots, while plants grown in South Sweden allocated more biomass to rhizomes. There was a regional origin effect as plants originating from North Sweden produced more biomass in both regions. Within the Northern region, plants from shaded habitats translocated more 14C to the rhizomes, suggesting more storage there than in plants from open habitats. In addition to genetic differentiation in biomass production between Northern and Southern populations, probably as a response to a shorter growing season in the North, there appeared to be genetic differentiation in physiological integration within the Northern region. This shows that both regional and local conditions need to be taken into account in future studies of genetic differentiation of physiological integration in clonal plants. 相似文献
20.
目的:探讨哮喘患者血清抗体及患者室内尘螨抗原浓度的季节变化规律。方法:2005年9月、2005年12月、2006年3月、2006年6月用ELISA法检测哮喘患者卧室尘样中Der P 1浓度,同步检测患者外周血总IgE、s-IgE、s-IgG1、s-IgG2和s-IgG4。结果:哮喘患者血清总IgE、s-IgE、s-IgG1、s-IgG2和s-IgG4均高于正常对照组,差异均具显著性(P<0.01);比较患者血清总IgE、s-IgE及s-IgG1、s-IgG2、s-IgG4四次检测值,差异均具显著性(P<0.01),患者血清总IgE、s-IgE在12月份检测值最高、6月份检测值最低,s-IgG1以6月份最高、3月份最低,s-IgG4在3月份最高、6月份最低。统计表明,患者卧室Der P1浓度四次检测值差异具有显著性(P<0.01),以2006年3月和2005年12月为高。结论:哮喘患者血清总IgE、s-IgE、s-IgC1、s-IgG2和s-IgG4和卧室尘螨抗原浓度呈季节变化,IgG1的变化与尘螨抗原浓度的变化趋势相反,IgG4的变化与尘螨抗原浓度的变化趋势一致。 相似文献