Rapid pneumococcal evolution in response to clinical interventions   总被引：1，自引：0，他引：1  

Croucher NJ  Harris SR  Fraser C  Quail MA  Burton J  van der Linden M  McGee L  von Gottberg A  Song JH  Ko KS  Pichon B  Baker S  Parry CM  Lambertsen LM  Shahinas D  Pillai DR  Mitchell TJ  Dougan G  Tomasz A  Klugman KP  Parkhill J  Hanage WP  Bentley SD 《Science (New York, N.Y.)》2011,331(6016):430-434

Epidemiological studies of the naturally transformable bacterial pathogen Streptococcus pneumoniae have previously been confounded by high rates of recombination. Sequencing 240 isolates of the PMEN1 (Spain(23F)-1) multidrug-resistant lineage enabled base substitutions to be distinguished from polymorphisms arising through horizontal sequence transfer. More than 700 recombinations were detected, with genes encoding major antigens frequently affected. Among these were 10 capsule-switching events, one of which accompanied a population shift as vaccine-escape serotype 19A isolates emerged in the USA after the introduction of the conjugate polysaccharide vaccine. The evolution of resistance to fluoroquinolones, rifampicin, and macrolides was observed to occur on multiple occasions. This study details how genomic plasticity within lineages of recombinogenic bacteria can permit adaptation to clinical interventions over remarkably short time scales.  相似文献   

Early Archaean microorganisms preferred elemental sulfur, not sulfate     

Philippot P  Van Zuilen M  Lepot K  Thomazo C  Farquhar J  Van Kranendonk MJ 《Science (New York, N.Y.)》2007,317(5844):1534-1537

Microscopic sulfides with low 34S/32S ratios in marine sulfate deposits from the 3490-million-year old Dresser Formation, Australia, have been interpreted as evidence for the presence of early sulfate-reducing organisms on Earth. We show that these microscopic sulfides have a mass-independently fractionated sulfur isotopic anomaly (Delta33S) that differs from that of their host sulfate (barite). These microscopic sulfides could not have been produced by sulfate-reducing microbes, nor by abiologic processes that involve reduction of sulfate. Instead, we interpret the combined negative delta34S and positive Delta33S signature of these microscopic sulfides as evidence for the early existence of organisms that disproportionate elemental sulfur.  相似文献   

CRISPR provides acquired resistance against viruses in prokaryotes     

Barrangou R  Fremaux C  Deveau H  Richards M  Boyaval P  Moineau S  Romero DA  Horvath P 《Science (New York, N.Y.)》2007,315(5819):1709-1712

Clustered regularly interspaced short palindromic repeats (CRISPR) are a distinctive feature of the genomes of most Bacteria and Archaea and are thought to be involved in resistance to bacteriophages. We found that, after viral challenge, bacteria integrated new spacers derived from phage genomic sequences. Removal or addition of particular spacers modified the phage-resistance phenotype of the cell. Thus, CRISPR, together with associated cas genes, provided resistance against phages, and resistance specificity is determined by spacer-phage sequence similarity.  相似文献   

High-quality binary protein interaction map of the yeast interactome network   总被引：1，自引：0，他引：1  

Yu H  Braun P  Yildirim MA  Lemmens I  Venkatesan K  Sahalie J  Hirozane-Kishikawa T  Gebreab F  Li N  Simonis N  Hao T  Rual JF  Dricot A  Vazquez A  Murray RR  Simon C  Tardivo L  Tam S  Svrzikapa N  Fan C  de Smet AS  Motyl A  Hudson ME  Park J  Xin X  Cusick ME  Moore T  Boone C  Snyder M  Roth FP  Barabási AL  Tavernier J  Hill DE  Vidal M 《Science (New York, N.Y.)》2008,322(5898):104-110

Current yeast interactome network maps contain several hundred molecular complexes with limited and somewhat controversial representation of direct binary interactions. We carried out a comparative quality assessment of current yeast interactome data sets, demonstrating that high-throughput yeast two-hybrid (Y2H) screening provides high-quality binary interaction information. Because a large fraction of the yeast binary interactome remains to be mapped, we developed an empirically controlled mapping framework to produce a "second-generation" high-quality, high-throughput Y2H data set covering approximately 20% of all yeast binary interactions. Both Y2H and affinity purification followed by mass spectrometry (AP/MS) data are of equally high quality but of a fundamentally different and complementary nature, resulting in networks with different topological and biological properties. Compared to co-complex interactome models, this binary map is enriched for transient signaling interactions and intercomplex connections with a highly significant clustering between essential proteins. Rather than correlating with essentiality, protein connectivity correlates with genetic pleiotropy.  相似文献   

Hidden degrees of freedom in aperiodic materials     

Toudic B  Garcia P  Odin C  Rabiller P  Ecolivet C  Collet E  Bourges P  McIntyre GJ  Hollingsworth MD  Breczewski T 《Science (New York, N.Y.)》2008,319(5859):69-71

Numerous crystalline materials, including those of bioorganic origin, comprise incommensurate sublattices whose mutual arrangement is described in a superspace framework exceeding three dimensions. We report direct observation by neutron diffraction of superspace symmetry breaking in a solid-solid phase transition of an incommensurate host-guest system: the channel inclusion compound of nonadecane/urea. Strikingly, this phase transition generates a unit cell doubling that concerns only the modulation of one substructure by the other-an internal variable available only in superspace. This unanticipated pathway for degrees of freedom to rearrange leads to a second phase transition, which again is controlled by the higher dimensionality of superspace. These results reveal nature's capacity to explore the increased number of phases allowed in aperiodic crystals.  相似文献   

Recombination and the nature of bacterial speciation     

Fraser C  Hanage WP  Spratt BG 《Science (New York, N.Y.)》2007,315(5811):476-480

Genetic surveys reveal the diversity of bacteria and lead to the questioning of species concepts used to categorize bacteria. One difficulty in defining bacterial species arises from the high rates of recombination that results in the transfer of DNA between relatively distantly related bacteria. Barriers to this process, which could be used to define species naturally, are not apparent. Here, we review conceptual models of bacterial speciation and describe our computer simulations of speciation. Our findings suggest that the rate of recombination and its relation to genetic divergence have a strong influence on outcomes. We propose that a distinction be made between clonal divergence and sexual speciation. Hence, to make sense of bacterial diversity, we need data not only from genetic surveys but also from experimental determination of selection pressures and recombination rates and from theoretical models.  相似文献   

Are ricefields a good alternative to natural marshes for waterbird communities in the Camargue, southern France?     

Christophe Tourenq  Robert E. Bennetts  Hubert Kowalski  Emmanuel Vialet  Jean-Laurent Lucchesi  Yves Kayser  Paul Isenmann 《Biological conservation》2001,100(3):335-343

Rice cultivation has frequently been suggested to provide an important wetland habitat for waterbirds. However, in contrast to most other regions of the Mediterranean, the Camargue still has a substantial amount of surface area of natural marshes. Thus, we compared the abundance, species richness, and community composition of waterbirds in ricefields and natural marshes of the Camargue, during a one-year study. Based on surveys conducted at 4–7 day intervals in 1997–1998, our results suggest that natural marshes had substantially greater abundance of waterbirds, with ca. 99% of the individuals having been observed in natural marshes. Estimates of species richness and associated parameters further indicated that ricefields were clearly less rich than natural marshes. Although our results were rather striking for the Camargue, they may not be applicable to other regions because of the relatively high availability of natural marshes and differences in management of ricefields.  相似文献   

Changes in physicochemical characteristics and volatile constituents of yellow- and white-fleshed nectarines during maturation and artificial ripening   总被引：5，自引：0，他引：5  

Aubert C  Günata Z  Ambid C  Baumes R 《Journal of agricultural and food chemistry》2003,51(10):3083-3091

Changes in the volatile composition during maturation and artificial ripening of yellow-fleshed nectarines were investigated by means of GC-FID and GC-MS over three years (1999-2001). Unripe and commercially ripe fruits were placed in ripening chambers until complete ripening and compared to tree-ripe nectarines. Firmness, weight, soluble solids (SS), titratable acidity (TA), SS/TA ratio, organic acids, and sugars were also determined. Furthermore, the tree-ripe and artificially ripened yellow-fleshed nectarines were subjected to sensory analysis by a taste panel. In 2001, a similar experiment on white-fleshed nectarines (cv. Vermeil) was performed to compare with the results obtained on yellow-fleshed nectarines. Levels of volatiles compounds, in particular, lactones and C(13) norisoprenoids, were found to be the same or higher in the artificially ripened nectarines compared with the tree-ripe nectarines. In addition, no significant difference was observed for sweetness, sourness, and the intensities of "peach odors" or "peach aroma" in the sensory analysis between the tree-ripe samples and the artificially ripened nectarines. However, in the latter the levels of SS and the SS/TA ratio were very close to those observed in the initial unripe samples and significantly lower than those observed in tree-ripe nectarines.  相似文献   

A high-throughput DNA extraction method for barley seed     

Rebecka von Post  Lars von Post  Christophe Dayteg  Marie Nilsson  Brian P. Forster  Stine Tuvesson 《Euphytica》2003,130(2):255-260

A non-destructive, quick DNA extraction method for barley seed is described. The method is simple and consists of drilling out a sample from the seed, adding sodium hydroxide, heating in a microwave oven and neutralizing with Tris-HCl. The seed DNA extract can be used directly for PCR with extra cycles added to the PCR programme compared to PCR programmes used for leaf extracts. This protocol was developed in particular for a micro satellite marker genetically linked to barley yellow mosaic virus resistance, but it can be applied toother markers of interest for barley breeding. The quick seed extraction protocol makes it possible to handle thousands of samples per day. Extraction of DNA from seed also facilitates transfer of plant material compared to the long-distance transfer of leaf samples. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Evaluation of the in vivo anthelmintic properties of Mitragyna inermis (Willd.) as a livestock dewormer against parasitic hematophagous worm Haemonchus contortus infections in different breeds of lambs     

Alowanou  Géorcelin Goué  Azando  Erick V. B.  Adenilé  Adam D.  Koudandé  Delphin O.  Chrysostome  Christophe A. M.  Hounzangbé-Adoté  Sylvie M. 《Tropical animal health and production》2020,52(1):309-319

Tropical Animal Health and Production - Gastrointestinal (GI) nematodes remain a major constraint on livestock production throughout the world. This study assessed the in vivo efficacy of the...  相似文献