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181.
Assessing horizontal transfer of nifHDK genes in eubacteria: nucleotide sequence of nifK from Frankia strain HFPCcI3 总被引:2,自引:1,他引:1
Hirsch AM; McKhann HI; Reddy A; Liao J; Fang Y; Marshall CR 《Molecular biology and evolution》1995,12(1):16-27
The structural genes for nitrogenase, nifK, nifD, and nifH, are crucial for
nitrogen fixation. Previous phylogenetic analysis of the amino acid
sequence of nifH suggested that this gene had been horizontally transferred
from a proteobacterium to the gram-positive/cyanobacterial clade, although
the confounding effects of paralogous comparisons made interpretation of
the data difficult. An additional test of nif gene horizontal transfer
using nifD was made, but the NifD phylogeny lacked resolution. Here nif
gene phylogeny is addressed with a phylogenetic analysis of a third and
longer nif gene, nifK. As part of the study, the nifK gene of the key taxon
Frankia was sequenced. Parsimony and some distance analyses of the nifK
amino acid sequences provide support for vertical descent of nifK, but
other distance trees provide support for the lateral transfer of the gene.
Bootstrap support was found for both hypotheses in all trees; the nifK data
do not definitively favor one or the other hypothesis. A parsimony analysis
of NifH provides support for horizontal transfer in accord with previous
reports, although bootstrap analysis also shows some support for vertical
descent of the orthologous nifH genes. A wider sampling of taxa and more
sophisticated methods of phylogenetic inference are needed to understand
the evolution of nif genes. The nif genes may also be powerful phylogenetic
tools. If nifK evolved by vertical descent, it provides strong evidence
that the cyanobacteria and proteobacteria are sister groups to the
exclusion of the firmicutes, whereas 16S rRNA sequences are unable to
resolve the relationships of these three major eubacterial lineages.
相似文献
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183.
Sara Castiglioni Clelia Caspani Alessandra Cazzaniga Jeanette AM Maier 《World journal of biological chemistry》2014,5(4):457-464
AIM: To study the response to silver nanoparticles (Ag NP) of human microvascular endothelial cells, protagonists of angiogenesis.METHODS: We cultured human microvascular endothelial cells and endothelial colony-forming cells in their corresponding growth medium. Stock solutions of Ag NP were prepared in culture medium and sonicated before use. They were added at different concentrations and for different times to culture media. The toxicity of Ag NP was investigated by measuring the reduction of yellow tetrazolium salt to dark purple formazan (MTT assay) at 575 nm. After staining with trypan blue, cell proliferation was assessed by counting viable cells. The lactate dehydrogenase leakage assay was performed on culture media by following the oxidation of NADH to NAD+ and monitoring the reaction kinetically at 340 nm. Reactive oxygen species production was quantified using 2’-7’-dichlorofluorescein diacetate. The alkaline comet assay was performed after mixing the cells with low melting-point agarose. Electrophoresis was then conducted and the samples were stained with ethidium bromide and analyzed with a fluorescence microscope.RESULTS: Ag NP are cytotoxic in a dose and time dependent fashion for HMEC. At high concentrations, Ag NP determine loss of membrane integrity as demonstrated by the increased activity of lactate dehydrogenase in the culture medium. Ag NP rapidly stimulate the formation of free radicals. However, pre-incubation with Trolox, apocynin, or N-acetyl-L-cysteine, antioxidants which have different structure and act through different mechanisms, is not sufficient to prevent cytotoxicity. Ag NP also induce DNA damage dose-dependently, as shown by comet assay. When exposed to sublethal concentrations of Ag NP for long times, the cells remain viable but are growth retarded. Interestingly, removal of Ag NP partially rescues cell growth. Also genotoxicity is reversible upon removal of Ag NP from culture medium, suggesting that no permanent modifications occur. It is noteworthy that Ag NP are cytotoxic and genotoxic also for endothelial progenitors, in particular for endothelial colony-forming cells, which participate to angiogenesis.CONCLUSION: Silver nanoparticles are cytotoxic and genotoxic for human microvascular endothelial cells and might become a useful tool to control excessive angiogenesis. 相似文献
184.
Michelle I Portugal Adriane R Todeschini Cristiana S de Lima Carlos AM Silva Ronaldo Mohana-Borges Tom HM Ottenhoff Lucia Mendonça-Previato Jose O Previato Maria CV Pessolani 《BMC microbiology》2008,8(1):75
Background
The histone-like Hlp protein is emerging as a key component in mycobacterial pathogenesis, being involved in the initial events of host colonization by interacting with laminin and glycosaminoglycans (GAGs). In the present study, nuclear magnetic resonance (NMR) was used to map the binding site(s) of Hlp to heparan sulfate and identify the nature of the amino acid residues directly involved in this interaction. 相似文献185.
Luís H Franco Pryscilla F Wowk Célio L Silva Ana PF Trombone Arlete AM Coelho-Castelo Constance Oliver Maria C Jamur Edson L Moretto Vânia LD Bonato 《Genetic vaccines and therapy》2008,6(1):1-11
Background
Application of plasmid DNA for immunization of food-producing animals established new standards of food safety. The addition of foreign products e.g. pDNA into the food chain should be carefully examined to ensure that neither livestock animals nor consumers develop unpredicted or undesirable side-effects.Methods
A quantitative real-time PCR (QRTPCR) methodology was developed to study the biodistribution and persistence of plasmid DNA vaccine pDNAX (pVAX-Hsp60 TM814) in mice and beef cattle. The linear quantification range and the sensitivity of the method was found to be 10 – 109 copies per reaction (500 ng/gDNA) and 3 copies per reaction, respectively.Results
Persistence of pDNAX in mice muscle tissue was restricted to injection site and the amount of pDNAX showed delivery formulation dependent (naked pDNA, electroporation, cationic liposome complexes) and mouse age-dependent clearance form injection site but pDNAX was still detectable even after 365 days. The QRTPCR analysis of various muscle tissue samples of vaccinated beef bulls performed 242–292 days after the last revaccination proved that residual pDNAX was found only in the injection site. The highest plasmid levels (up to 290 copies per reaction) were detected in the pDNAX:CDAN/DOPE group similarly to mice model. No pDNA was detected in the samples from distant muscles and draining lymph nodes.Conclusion
Quantitative real-time PCR (QRTPCR) assay was developed to assess the residual pDNA vaccine pVAX-Hsp60 TM814 in mice and beef cattle. In beef cattle, ultra low residual level of pDNA vaccine was only found at the injection site. According to rough estimation, consumption of muscles from the injection site represents almost an undetectable intake of pDNA (400 fg/g muscle tissue) for consumers. Residual plasmid in native state will hardly be found at measurable level following further meat processing. This study brings supportive data for animal and food safety and hence for further approval of pDNA vaccine field trials. 相似文献186.
Solomon Gizaw Hans Komen Jack J Windig Olivier Hanotte Johan AM van Arendonk 《遗传、选种与进化》2008,40(4):433-447
Prioritizing livestock breeds for conservation needs to incorporate both genetic and non-genetic aspects important for the survival of the breeds. Here, we apply a maximum-utility-strategy to prioritize 14 traditional Ethiopian sheep breeds based on their threat status, contributions to farmer livelihoods (current breed merits) and contributions to genetic diversity. Contributions of the breeds to genetic diversity were quantified using Eding''s marker-estimated kinship approaches. Non-genetic aspects included threats (e.g. low population size, low preferences by farmers) and current merits (economic, ecological and cultural merits). Threat analysis identified eight of the 14 breeds as threatened. Analysis of current merits showed that sub-alpine and arid-lowland breeds contribute most to farmer livelihoods in comparison to other breeds. The highest contribution to the genetic diversity conserved was from the Simien breed. Simien showed high between-breed (low between-breed kinship = 0.04) as well as high within-breed diversity (low within-breed kinship = 0.09 and high HE = 0.73 and allelic richness = 6.83). We combined the results on threat status, current breed merits and contributions to genetic diversity to produce a ranking of the 14 breeds for conservation purposes. Our results balance the trade-offs between conserving breeds as insurance against future uncertainties and current sustainable utilization. The ranking of breeds provides a basis for conservation strategies for Ethiopian sheep and contributes to a regional or global conservation plan. 相似文献
187.
188.
Colin?AM?SempleEmail author Alison?Maxwell Philippe?Gautier Fiona?M?Kilanowski Hayden?Eastwood Perdita?E?Barran Julia?R?Dorin 《BMC evolutionary biology》2005,5(1):32
Background
We have examined the evolution of the genes at the major human β-defensin locus and the orthologous loci in a range of other primates and mouse. For the first time these data allow us to examine selective episodes in the more recent evolutionary history of this locus as well as the ancient past. We have used a combination of maximum likelihood based tests and a maximum parsimony based sliding window approach to give a detailed view of the varying modes of selection operating at this locus. 相似文献189.
Kinetoplastida are protozoan organisms that probably diverged early in evolution from other eukaryotes. They are characterized
by a number of unique features with respect to their energy and carbohydrate metabolism. These organisms possess peculiar
peroxisomes, called glycosomes, which play a central role in this metabolism; the organelles harbour enzymes of several catabolic
and anabolic routes, including major parts of the glycolytic and pentosephosphate pathways. The kinetoplastid mitochondrion
is also unusual with regard to both its structural and functional properties. 相似文献
190.