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Immunofluorescence serology. A tool for prognosis of Q-fever   总被引:3,自引:0,他引:3  
The indirect immunofluorescence antibody test is currently the method of choice for Q-fever laboratory diagnosis. It permits the detection of IgG-, IgM-, and IgA-specific antibodies against the two phases of Coxiella burnetii. Sera from 20 cases of C. burnetii infection have been examined. Only total IgG against phase II were detected in cryptic infections. In acute Q-fever cases, the appearance of total IgG antibodies against phase I was a sign of aggravation, while IgM titers remained low. In subacute cases of Q-fever, anti-phase-I IgG titers were equal to or higher than anti-phase-II titers, and IgM against both phases were produced over a long time. Particularly high IgM titers were found in cases of granulomatous hepatitis. IgA antibodies against phase I were found in cases of Q-fever endocarditis, although the two cases that died had few or no IgA antibodies, despite very high IgG and IgM titers.  相似文献   
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Animal gastrointestinal tracts harbor a microbiome that is integral to host function, yet species from diverse phyla have evolved a reduced digestive system or lost it completely. Whether such changes are associated with alterations in the diversity and/or abundance of the microbiome remains an untested hypothesis in evolutionary symbiosis. Here, using the life history transition from planktotrophy (feeding) to lecithotrophy (nonfeeding) in the sea urchin Heliocidaris, we demonstrate that the lack of a functional gut corresponds with a reduction in microbial community diversity and abundance as well as the association with a diet-specific microbiome. We also determine that the lecithotroph vertically transmits a Rickettsiales that may complement host nutrition through amino acid biosynthesis and influence host reproduction. Our results indicate that the evolutionary loss of a functional gut correlates with a reduction in the microbiome and the association with an endosymbiont. Symbiotic transitions can therefore accompany life history transitions in the evolution of developmental strategies.

Animal gastrointestinal tracts contain microbial communities that are integral to host metabolism, immunity, and development (1, 2). Symbioses between animals and their gut microbiome have deep evolutionary origins (1, 2), often exhibit phylosymbiosis (3), and can serve as a physiological buffer to heterogeneous environments (2). Despite the necessity of the gastrointestinal tract and benefits of the gut microbiome (3), species in various phyla have lost a functional digestive system (4, 5). Loss of a functional gut should, in theory, cascade into a reduction in microbial diversity and the loss of diet-induced shifts in microbiome composition. These nutritional shifts may then provide a niche for functionally important endosymbionts, such as the chemoautotrophic bacteria commonly associated with gutless invertebrates (6, 7).Major life history transitions are driven by tradeoffs in reproduction and development that, in turn, impact fitness (8). These tradeoffs are particularly evident in benthic marine invertebrates whose developmental stages broadly group into two alternative nutritional strategies (4, 9). The first—planktotrophy—typically includes the production of a high number of small, energy-poor eggs that develop into larvae with feeding structures used to collect and process exogenous resources required to reach metamorphic competency (4, 9). The second—lecithotrophy—involves the production of fewer large, energy-rich eggs and nonfeeding larvae that undergo metamorphosis without the requirement of external nutrients through feeding (4, 9). Life history transitions between these developmental modes have occurred in several major animal lineages, with rapid evolutionary shifts from planktotrophy to lecithotrophy being well documented in echinoderms (4, 5, 1013). It is thought that an increase in the eggs energetic content relaxes the selective pressure maintaining the feeding structures (e.g., the larval arms and a functional gastrointestinal tract) and that development to metamorphosis is accelerated once these are lost (5).One of the most comprehensively studied systems for life history transitions among marine invertebrates involves species in the sea urchin genus Heliocidaris. A speciation event ∼5 Mya resulted in two sister species with alternative life history strategies: Heliocidaris tuberculata is planktotrophic while Heliocidaris erythrogramma is lecithotrophic (14). Typical of planktotrophs, H. tuberculata develops from small eggs into feeding larvae that exhibit morphological plasticity in response to food limitation (15), which is correlated with compositional shifts in the microbiome (16, 17). H. erythrogramma, on the other hand, develops from eggs ∼53× to 86× the volume of H. tuberculata (18), lacks the morphological structures required for feeding, and has a reduced, nonfunctional digestive tract (11). This life history switch and heterochronic shift in development (11) corresponds with a rewiring of the gene regulatory network (19), reorganization of cell fates (20), and modification to gametogenesis (21).Here, we compare the bacterial communities of these Heliocidaris species and test two hypotheses. First, we test whether the loss of gut function coincides with a reduction in microbial symbiont diversity, and second, by simulating the natural range in food availability, we also test that the loss in gut function coincides with a loss in diet-related shifts in the microbiome. We report major reductions in microbiome diversity and abundance as well as the absence of bacterial communities correlated with food availability for the lecithotrophic H. erythrogramma. Moreover, we find that this species vertically transmits a Rickettsiales that encodes pathways for the biosynthesis of essential amino acids, proteins with pivotal roles in host reproduction, and enzymes to metabolize diacylglycerol ethers, the major lipid group responsible for the increase in egg size in H. erythrogramma and that is used to fuel growth and development (18, 22).  相似文献   
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Most parthenogenetic weevil species are postulated to have originated via hybridization, but Wolbachia has also been speculated to play a role via the induction of parthenogenesis. Here, we examine the molecular diversity of Wolbachia and parthenogenetic host genomes. The host species studied here, Eusomus ovulum, is known to be exclusively parthenogenetic and triploid. The E. ovulum populations that we examined had a low genetic diversity of mitochondrial (cytochrome oxidase I gene) and nuclear markers (internal transcribed spacer 2 and elongation factor 1‐ α gene), and they all were infected by only single bacteria strains (genotyped for five genes according to the multilocus sequence typing system). We found significant signs of linkage disequilibrium and a lack of recombination amongst all of the examined genomes (bacteria and host), which strongly indicates a selective sweep. The lack of heterozygosity in host nuclear genes, missing bisexual populations and selective sweep between the parthenogenetic host and bacteria genomes suggest that parthenogenesis in this species could have originated as a result of infection rather than hybridization. However, the finding that highly similar Wolbachia strains are also present in other parthenogenetic weevils from the same habitat suggests the opposite scenario: bacteria may have infected the already parthenogenetic lineage and taken advantage of the host's unisexual reproduction.  相似文献   
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Alpha (α) proteobacteria comprise a large and metabolically diverse group. No biochemical or molecular feature is presently known that can distinguish these bacteria from other groups. The evolutionary relationships among this group, which includes numerous pathogens and agriculturally important microbes, are also not understood. Shared conserved inserts and deletions (i.e., indels or signatures) in molecular sequences provide a powerful means for identification of different groups in clear terms, and for evolutionary studies (see www.bacterialphylogeny.com). This review describes, for the first time, a large number of conserved indels in broadly distributed proteins that are distinctive and unifying characteristics of either all α ?proteobacteria, or many of its constituent subgroups (i.e., orders, families, etc.). These signatures were identified by systematic analyses of proteins found in the Rickettsia prowazekii(RP) genome. Conserved indels that are unique to α ?proteobacteria are present in the following proteins: Cytochrome c oxidase assembly protein Ctag, PurC, DnaB, ATP synthase α ?subunit, exonuclease VII, prolipoprotein phosphatidylglycerol transferase, RP?400, FtsK, puruvate phosphate dikinase, cytochrome b, MutY, and homoserine dehydrogenase. The signatures in succinyl?CoA synthetase, cytochrome oxidase I, alanyl?tRNA synthetase, and MutS proteins are found in all α ?proteobacteria, except the Rickettsiales, indicating that this group has diverged prior to the introduction of these signatures. A number of proteins contain conserved indels that are specific for Rickettsiales(XerD integrase and leucine aminopeptidase),Rickettsiaceae(Mfd, ribosomal protein L19, FtsZ, Sigma 70 and exonuclease VII), or Anaplasmataceae(Tgt and RP?314), and they distinguish these groups from all others. Signatures in DnaA, RP?057, and DNA ligase A are commonly shared by various Rhizobiales, Rhodobacterales, and Caulobacter, suggesting that these groups shared a common ancestor exclusive of other α ?proteobacteria. A specific relationship between Rhodobacterales and Caulobacter is indicated by a large insert in the Asn?Gln amidotransferase. TheRhizobiales group of species are distinguished from others by a large insert in the Trp?tRNA synthetase. Signature sequences in a number of other proteins (viz. oxoglutarate dehydogenase, succinyl?CoA synthase, LytB, DNA gyrase A, LepA, and Ser?tRNA synthetase) serve to distinguish the Rhizobiaceae, Brucellaceae, and Phyllobacteriaceae families from Bradyrhizobiaceae and Methylobacteriaceae. Based on the distribution patterns of these signatures, it is now possible to logically deduce a model for the branching order among α ?proteobacteria, which is as follows: Rickettsiales → Rhodospirillales?Sphingomonadales → Rhodobacterales?Caulobacterales → Rhizobiales(Rhizobiaceaea?Brucellaceae?Phyllobacteriaceae, and Bradyrhizobiaceae). The deduced branching order is also consistent with the topologies in the 16 rRNA and other phylogenetic trees. Signature sequences in a number of other proteins provide evidence that α ?proteobacteria is a late branching taxa within Bacteria, which branched after the δ,? ?subdivisions but prior to the β,γ?proteobacteria. The shared presence of many of these signatures in the mitochondrial (eukaryotic) homologs also provides evidence of the α ?proteobacterial ancestry of mitochondria.  相似文献   
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High incidence of Coxiella burnetii markers in a rural population in France   总被引:1,自引:0,他引:1  
Since Coxiella burnetii, the causative agent of Q fever, is often transmitted from goats and sheep to humans through aerosols, we examined the sera from 168 persons involved in goat breeding in the Centre region of France and 40 members of veterinary and medical staff from the same region for the presence of antibodies against C. burnetii. An immunofluorescence assay was used to detect the presence of antibodies of the IgG isotope against epitopes from phase II of C. burnetii, which are the first antibodies to appear in infected people, and from phase I, which reflect more chronic stages of the infection. Our serological survey showed that most of the tested sera were positive for C. burnetii markers, indicating at least an encounter with the bacterium. In the overall population of 208 subjects, 71% of the sera had antibodies against phase II epitopes (titres 1:40). Among the goat farmers and their immediate families, 78% had antibodies against phase II and 33% against phase I (titres 1:40). Considering only high titres ( 1:320), though, only 37% of the farmers had antibodies against phase II and 15% against phase 1. Only 3 out of 12 veterinarians working in the field had high titres of antibodies against phase II and phase I, while none of 28 members of veterinary and medical laboratories had significant levels of antibodies. These results emphasize the need for closer surveillance of populations at risk for Q fever, to prevent the infection by C. burnetii from reaching chronic stages of the disease.  相似文献   
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目的 建立及优化检测立克次体目中7种重要病原菌的TaqMan-探针实时荧光定量PCR(qPCR)方法,可同步检测并明确感染类型。方法 根据普氏立克次体、莫氏立克次体和斑点热群立克次体ompB基因、恙虫病东方体groEL基因、查菲埃立克体16S rRNA基因、嗜吞噬细胞无形体gltA基因和贝氏柯克斯体com1基因序列合成引物和探针,优化反应体系及反应程序至同一方案,对该方法灵敏度、特异性和重复性等进行评价,并使用该方法对模拟样本和实际样本进行检测。结果 7种病原菌标准曲线的Ct值与模板拷贝数均呈良好的线性关系(均R2>0.990 0),所建立方法最低检测限均为1×10拷贝数/μl且具有良好的特异性。96份蜱虫核酸提取物样本中,1份样本检出贝氏柯克斯体,3份样本检出斑点热群立克次体;80份不明原因发热患者血标本DNA中,1份样本检出恙虫病东方体,2份样本检出斑点热群立克次体。结论 本研究基于TaqMan-探针qPCR方法,将7种病原菌反应体系及反应程序优化至同一方案,克服目前不同立克次体目病原菌采用不同的反应体系和反应程序的缺点,可将临床样本中立克次体目的7种重要病原菌精确定位检测至种,明确感染病原菌类型并缩短检测时间,有助于对患者的精准诊治。  相似文献   
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