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排序方式: 共有692条查询结果,搜索用时 15 毫秒
611.
The pollinator-driven ecological speciation model has frequently been invoked to explain plant richness in biodiversity hotspots. Here, by focusing on Gladiolus (260 species), a flagship example of a clade with diverse pollination biology, we test the hypothesis that high species diversity in southern Africa, one of the world's most floristically rich regions, has primarily been driven by ecological shifts in pollination systems. We use phylogenetic methods to estimate rates of transition between the seven highly specialized pollination strategies in Gladiolus. We find that pollination systems have evolved multiple times and that some pollination strategies arose by a variety of evolutionary pathways. Pollination shifts account for up to one-third of all lineage splitting events in the genus, providing partial support for the pollinator-driven speciation model. Transitions from the ancestral pollination mode to derived systems have also resulted in increased rates of diversification, suggesting that certain pollination systems may speed up speciation processes, independently of pollination shifts per se. This study suggests that frequent pollination shifts have played a role in driving high phenotypic and species diversity but indicates that additional factors need to be invoked to account for the spectacular diversification in southern African Gladiolus. 相似文献
612.
Pereira LF Bassi AP Avansini SH Neto AG Brasileiro BT Ceccato-Antonini SR de Morais MA 《Antonie van Leeuwenhoek》2012,101(3):529-539
The yeast Dekkera bruxellensis plays an important role in industrial fermentation processes, either as a contaminant or as a fermenting yeast. In this study,
an analysis has been conducted of the fermentation characteristics of several industrial D. bruxellensis strains collected from distilleries from the Southeast and Northeast of Brazil, compared with Saccharomyces cerevisiae. It was found that all the strains of D. bruxellensis showed a lower fermentative capacity as a result of inefficient sugar assimilation, especially sucrose, under anaerobiosis,
which is called the Custer effect. In addition, most of the sugar consumed by D. bruxellensis seemed to be used for biomass production, as was observed by the increase of its cell population during the fermentation
recycles. In mixed populations, the surplus of D. bruxellensis over S. cerevisiae population could not be attributed to organic acid production by the first yeast, as previously suggested. Moreover, both
yeast species showed similar sensitivity to lactic and acetic acids and were equally resistant to ethanol, when added exogenously
to the fermentation medium. Thus, the effects that lead to the employment of D. bruxellensis in an industrial process and its effects on the production of ethanol are multivariate. The difficulty of using this yeast
for ethanol production is that it requires the elimination of the Custer effect to allow an increase in the assimilation of
sugar under anaerobic conditions. 相似文献
613.
Decisions guiding environmental management need to be based on a broad and comprehensive understanding of the biodiversity and functional capability within ecosystems. Microbes are of particular importance since they drive biogeochemical cycles, being both producers and decomposers. Their quick and direct responses to changes in environmental conditions modulate the ecosystem accordingly, thus providing a sensitive readout. Here we have used direct sequencing of total DNA from water samples to compare the microbial communities of two distinct coastal regions exposed to different anthropogenic pressures: the highly polluted Port of Genoa and the protected area of Montecristo Island in the Mediterranean Sea. Analysis of the metagenomes revealed significant differences in both microbial diversity and abundance between the two areas, reflecting their distinct ecological habitats and anthropogenic stress conditions. Our results indicate that the combination of next generation sequencing (NGS) technologies and bioinformatics tools presents a new approach to monitor the diversity and the ecological status of aquatic ecosystems. Integration of metagenomics into environmental monitoring campaigns should enable the impact of the anthropogenic pressure on microbial biodiversity in various ecosystems to be better assessed and also predicted. 相似文献
614.
Valente C Hinds J Pinto F Brugger SD Gould K Mühlemann K de Lencastre H Sá-Leão R 《PloS one》2012,7(1):e30235
Understanding the epidemiology of pneumococcal co-colonization is important for monitoring vaccine effectiveness and the occurrence of horizontal gene transfer between pneumococcal strains. In this study we aimed to evaluate the impact of the seven-valent pneumococcal conjugate vaccine (PCV7) on pneumococcal co-colonization among Portuguese children. Nasopharyngeal samples from children up to 6 years old yielding a pneumococcal culture were clustered into three groups: pre-vaccine era (n = 173), unvaccinated children of the vaccine era (n = 169), and fully vaccinated children (4 doses; n = 150). Co-colonization, serotype identification, and relative serotype abundance were detected by analysis of DNA of the total bacterial growth of the primary culture plate using the plyNCR-RFLP method and a molecular serotyping microarray-based strategy. The plyNCR-RFLP method detected an overall co-colonization rate of 20.1%. Microarray analysis confirmed the plyNCR-RFLP results. Vaccination status was the only factor found to be significantly associated with co-colonization: co-colonization rates were significantly lower (p = 0.004; Fisher''s exact test) among fully vaccinated children (8.0%) than among children from the pre-PCV7 era (17.3%) or unvaccinated children of the PCV7 era (18.3%). In the PCV7 era there were significantly less non-vaccine type (NVT) co-colonization events than would be expected based on the NVT distribution observed in the pre-PCV7 era (p = 0.024). In conclusion, vaccination with PCV7 resulted in a lower co-colonization rate due to an asymmetric distribution between NVTs found in single and co-colonized samples. We propose that some NVTs prevalent in the PCV7 era are more competitive than others, hampering their co-existence in the same niche. This result may have important implications since a decrease in co-colonization events is expected to translate in decreased opportunities for horizontal gene transfer, hindering pneumococcal evolution events such as acquisition of antibiotic resistance determinants or capsular switch. This might represent a novel potential benefit of conjugate vaccines. 相似文献
615.
616.
Association of interleukin-(IL)10 haplotypes and serum IL-10 levels in the progression of childhood immune thrombocytopenic purpura 总被引:1,自引:0,他引:1
Derangement of genetic and immunological factors seems to have a pivotal role in the pathophysiology of immune thrombocytopenic purpura (ITP). We investigated interleukin(IL)-10 genetically determined expression in children with an acute progression of ITP (n=41) compared to young patients with chronic ITP (n=44) and healthy controls (n=60), and attempted to correlate IL-10 production with the course of the disease. We genotyped our study population for three single nucleotide polymorphisms at positions -1082 (A/G), -819 (C/T) and -592 (C/A) in the promoter region of the IL-10 gene. IL-10 levels were measured by enzyme-linked immunoassay. The IL-10 production in our study population was significantly higher in patients carrying the GCC haplotype than those bearing ACC and ATA haplotypes (6.9 ± 1.5 vs 3.6 ± 0.8 vs 3.3 ± 0.3, p=0.03). The serum concentration of IL-10 was significantly higher in patients with an acute course of their disease, who mainly carried the GCC haplotype (92%), compared to chronic subjects, bearing the non-GCC haplotypes, and controls [17 pg/mL (1.7-18) vs 3.5 pg/mL (0.6-11) vs 3 pg/mL (1-7), p<0.01)]. Our findings show that patients carrying the GCC-high producer IL-10 haplotype have an acute development of ITP and that IL-10 levels might represent a useful predictive biomarker of the disease course. 相似文献
617.
Giselle V.F. Brunoro Rubem F.S. Menna-Barreto Aline S. Garcia-Gomes Carolina Boucinha Diogo B. Lima Paulo C. Carvalho André Teixeira-Ferreira Monique R.O. Trugilho Jonas Perales Veit Schwämmle Marcos Catanho Ana Tereza R. de Vasconcelos Maria Cristina M. Motta Claudia M. d’Avila-Levy Richard H. Valente 《Protist》2019,170(6):125698
618.
Mariana Fensterseifer Fabricio Patricia Valente Marco Antônio Záchia Ayub 《Biotechnology progress》2019,35(6):e2895
We studied the biotechnological potential of the recently isolated yeast Meyerozyma guilliermondii BI281A to produce polyunsaturated fatty acids and ethanol, comparing products yields using glucose, raw glycerol from biodiesel synthesis, or whey permeate as substrates. The yeast metabolism was evaluated for different C/N ratios (100:1 and 50:1). Results found that M. guilliermondii BI281A was able to assimilate all tested substrates, and the most efficient conversion obtained was observed using raw glycerol as carbon source (C/N ratio 50:1), concerning biomass formation (5.67 g·L−1) and lipid production (1.04 g·L−1), representing 18% of dry cell weight. Bioreactors experiments under pH and aeration-controlled conditions were conducted. Obtained fatty acids were composed of ~67% of unsaturated fatty acids, distributed as palmitoleic acid (C16:1, 9.4%), oleic acid (C18:1, 47.2%), linoleic acid (C18:2 n−6, 9.6%), and linolenic acid (C18:3 n−3, 1.3%). Showing fermentative metabolism, which is unusual for oleaginous yeasts, M. guilliermondii produced 13.7 g·L−1 of ethanol (yields of 0.27) when growing on glucose medium. These results suggest the promising use of this uncommonly studied yeast to produce unsaturated fatty acids and ethanol using cheap agro-industrial residues as substrates in bioprocess. 相似文献
619.
PW2 is an anticoccidial peptide active against Eimeria acervulina and Eimeria tenella. We determined the structure of PW2 in dodecylphosphocholine micelles. The structure showed two distinct regions: an amphipathic
N-terminal 310 helix and an aromatic region containing WWR interface-binding motif. The aromatic region acted as a scaffold of the protein
in the interface and shared the same structure in both DPC and SDS micelles. N-terminal helix interacted with DPC but not
with SDS interface. Chemical shift change was slow when SDS was added to PW2 in DPC and fast when DPC was added to PW2 in
SDS, indicating that interaction with DPC micelles was kinetically more stable than with SDS micelles. Also, DPC interface
was able to accommodate PW2, but it maintained the conformational arrangement in the aromatic region observed for SDS micelles.
This behavior, which is different from that observed for other antimicrobial peptides with WWR motif, may be associated with
the absence of PW2 antibacterial activity and its selectivity for Eimeria parasites.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Deposits: PDB code 2JQ2 and BMRB accession number 15267. 相似文献
620.
Acute Alterations of Glutamate,Glutamine, GABA,and Other Amino Acids After Spinal Cord Contusion in Rats 总被引:1,自引:0,他引:1
Diaz-Ruiz A Salgado-Ceballos H Montes S Maldonado V Tristan L Alcaraz-Zubeldia M Ríos C 《Neurochemical research》2007,32(1):57-63
Spinal cord injury (SCI) leads to an alteration of energetic metabolism. As a consequence, glutamate, glutamine, aspartate
and other important amino acids are altered after damage, leading to important disregulation of the neurochemical pathways.
In the present study, we characterized the acute-phase changes in tissue concentration of amino acids involved in neurotransmitter
and non-neurotransmitter actions after SCI by contusion in rats. Animals were submitted to either laminectomy or SCI by contusion
and sacrificed at 2, 4, 8, and 12 h after lesion, for the analysis of tissue amino acids by HPLC. Results showed that both
aspartate and glutamate contents diminished after SCI, while glutamine concentrations raised, however, the sum of molar concentrations
of glutamate plus glutamine remained unchanged at all time points. GABA concentrations increased versus control group, while
glycine remained unchanged. Finally, citrulline levels increased by effect of SCI, while taurine-increased only 4 h after
lesion. Results indicate complex acute-phase changes in amino acids concentrations after SCI, reflecting the different damaging
processes unchained after lesion. 相似文献