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341.
Catherine E Chambers Erika I Lutter Michelle B Visser Peggy PY Law Pamela A Sokol 《BMC microbiology》2006,6(1):104-19
Background
The Burkholderia cenocepacia CepIR quorum sensing system has been shown to positively and negatively regulate genes involved in siderophore production, protease expression, motility, biofilm formation and virulence. In this study, two approaches were used to identify genes regulated by the CepIR quorum sensing system. Transposon mutagenesis was used to create lacZ promoter fusions in a cepI mutant that were screened for differential expression in the presence of N-acylhomoserine lactones. A bioinformatics approach was used to screen the B. cenocepacia J2315 genome for CepR binding site motifs. 相似文献342.
343.
Juan Liao Humberto B. Jijon Ira R. Kim Gautam Goel Aivi Doan Harry Sokol Hermann Bauer Bernhard G. Herrmann Kara G. Lassen Ramnik J. Xavier 《PloS one》2014,9(9)
The pathogenesis of complex diseases, such as type 1 diabetes (T1D), derives from interactions between host genetics and environmental factors. Previous studies have suggested that viral infection plays a significant role in initiation of T1D in genetically predisposed individuals. T1D susceptibility loci may therefore be enriched in previously uncharacterized genes functioning in antiviral defense pathways. To identify genes involved in antiviral immunity, we performed an image-based high-throughput genetic screen using short hairpin RNAs (shRNAs) against 161 genes within T1D susceptibility loci. RAW 264.7 cells transduced with shRNAs were infected with GFP-expressing herpes simplex virus type 1 (HSV-1) and fluorescent microscopy was performed to assess the viral infectivity by fluorescence reporter activity. Of the 14 candidates identified with high confidence, two candidates were selected for further investigation, Il27 and Tagap. Administration of recombinant IL-27 during viral infection was found to act synergistically with interferon gamma (IFN-γ) to activate expression of type I IFNs and proinflammatory cytokines, and to enhance the activities of interferon regulatory factor 3 (IRF3). Consistent with a role in antiviral immunity, Tagap-deficient macrophages demonstrated increased viral replication, reduced expression of proinflammatory chemokines and cytokines, and decreased production of IFN-β. Taken together, our unbiased loss-of-function genetic screen identifies genes that play a role in host antiviral immunity and delineates roles for IL-27 and Tagap in the production of antiviral cytokines. 相似文献
344.
Evolutionary transfer of ORF-containing group I introns between different subcellular compartments (chloroplast and mitochondrion) 总被引:8,自引:2,他引:8
Turmel M; Cote V; Otis C; Mercier JP; Gray MW; Lonergan KM; Lemieux C 《Molecular biology and evolution》1995,12(4):533-545
We describe here a case of homologous introns containing homologous open
reading frames (ORFs) that are inserted at the same site in the large
subunit (LSU) rRNA gene of different organelles in distantly related
organisms. We show that the chloroplast LSU rRNA gene of the green alga
Chlamydomonas pallidostigmatica contains a group I intron (CpLSU.2)
encoding a site-specific endonuclease (I-CpaI). This intron is inserted at
the identical site (corresponding to position 1931-1932 of the Escherichia
coli 23S rRNA sequence) as a group I intron (AcLSU.m1) in the mitochondrial
LSU rRNA gene of the amoeboid protozoon Acanthamoeba castellanii. The
CpLSU.2 intron displays a remarkable degree of nucleotide similarity in
both primary sequence and secondary structure to the AcLSU.m1 intron;
moreover, the Acanthamoeba intron contains an ORF in the same location
within its secondary structure as the CpLSU.2 ORF and shares with it a
strikingly high level of amino acid similarity (65%; 42% identity). A
comprehensive survey of intron distribution at site 1931 of the chloroplast
LSU rRNA gene reveals a rather restricted occurrence within the
polyphyletic genus Chlamydomonas, with no evidence of this intron among a
number of non- Chlamydomonad green algae surveyed, nor in land plants. A
parallel survey of homologues of a previously described and similar
intron/ORF pair (C. reinhardtii chloroplast CrLSU/A. castellanii
mitochondrial AcLSU.m3) also shows a restricted occurrence of this intron
(site 2593) among chloroplasts, although the intron distribution is
somewhat broader than that observed at site 1931, with site-2593 introns
appearing in several green algal branches outside of the Chlamydomonas
lineage. The available data, while not definitive, are most consistent with
a relatively recent horizontal transfer of both site-1931 and site- 2593
introns (and their contained ORFs) between the chloroplast of a
Chlamydomonas-type organism and the mitochondrion of an Acanthamoeba- like
organism, probably in the direction chloroplast to mitochondrion. The data
also suggest that both introns could have been acquired in a single event.
相似文献
345.
346.
Frantisek Sokol Ernest Kuwert Tadeusz J. Wiktor Klaus Hummeler Hilary Koprowski 《Journal of virology》1968,2(8):836-849
Extracellular rabies virus, grown in monolayer cultures of BHK21 cells in the presence of medium supplemented with bovine serum albumin, was purified by the following procedure. Virus was precipitated from infectious tissue culture fluid by zinc acetate and was resuspended in a solution of ethylenediaminetetraacetate. The suspension was filtered through a Sephadex column and was treated with ribonuclease and deoxyribonuclease. The virions were then pelleted by centrifugation at high speed and were resuspended in buffer solution. Banding of the virus by centrifugation in a sucrose density gradient was the final step in the purification procedure. Purified preparations contained bullet-shaped virus particles of variable length and little (up to 5%) contaminating host-cell material. Most of the virions were "complete", i.e., 180 nm long, but some virus particles were shorter. The length distribution of the virions was nonrandom. Shorter virions seemed to be noninfectious and showed markedly decreased hemagglutinating activity. The complement-fixing activity and the ribonucleic acid to protein ratio of the virions were not related to the length of the virus particles. Although the properties of extracellular and intracellular viruses were similar, the procedure was not suitable for purification of intracellular rabies virus. 相似文献
347.
W M St John T A Bledsoe H W Sokol 《Journal of applied physiology (Bethesda, Md. : 1985)》1984,56(4):1008-1019
We hypothesized that a discrete medullary locus, critical for gasping neurogenesis, could be identified. In decerebrate, cerebellectomized, vagotomized, paralyzed, and ventilated cats, activities of phrenic, hypoglossal, and recurrent laryngeal nerves were monitored. Gasping was induced by freezing the brain stem, via a fork thermode, at the pontomedullary junction. By reversible cooling of the medulla, chemical lesions with kainic acid, and radio-frequency lesions, a critical area for gasping neurogenesis was localized bilaterally 2-3 mm rostral to obex, 2.0-2.5 mm lateral to midline, and 3-4 mm ventral to medullary surface. Electrical stimulation in this area elicited premature gasps, whereas unilateral lesions or lidocaine injections eliminated gasping activities in all nerves. These procedures did not cause similar changes during eupnea. In apneusis, however, lidocaine injections markedly altered the pattern or caused apnea. We conclude that discharge of neurons in a discrete portion of the lateral tegmental field of medulla is required for gasping neurogenesis. Our results are consistent with these neurons comprising the central pattern generator for gasping. 相似文献
348.
Background
Bacteria use N-acyl homoserine lactone (AHL) molecules to regulate the expression of genes in a density-dependent manner. Several biosensors have been developed and engineered to detect the presence of all types of AHLs.Results
In this study, we describe the usefulness of a traI-luxCDABE-based biosensor to quickly detect AHLs from previously characterized mutants of Burkholderia cenocepacia and Pseudomonas aeruginosa in both liquid and soft-agar co-culture assays in a high-throughput manner. The technique uses a co-culture system where the strain producing the AHLs is grown simultaneously with the reporter strain. Use of this assay in liquid co-culture allows the measurement of AHL activity in real time over growth. We tested this assay with Burkholderia cenocepacia and Pseudomonas aeruginosa but it should be applicable to a broad range of gram negative species that produce AHLs.Conclusion
The co-culture assays described enable the detection of AHL production in both P. aeruginosa and B. cenocepacia and should be applicable to AHL analysis in other bacterial species. The high-throughput adaptation of the liquid co-culture assay could facilitate the screening of large libraries for the identification of mutants or compounds that block the synthesis or activity of AHLs. 相似文献349.
Publication of the complete diploid genome sequence of the yeast Candida albicans will accelerate research into the pathogenesis of Candida infections. Comparative genomic analysis highlights genes that may contribute to C. albicans survival and its fitness as a human commensal and pathogen. 相似文献
350.
The robustness of two phylogenetic methods: four-taxon simulations reveal a slight superiority of maximum likelihood over neighbor joining 总被引:3,自引:3,他引:3
The robustness (sensitivity to violation of assumptions) of the maximum-
likelihood and neighbor-joining methods was examined using simulation.
Maximum likelihood and neighbor joining were implemented with Jukes-
Cantor, Kimura, and gamma models of DNA substitution. Simulations were
performed in which the assumptions of the methods were violated to varying
degrees on three model four-taxon trees. The performance of the methods was
evaluated with respect to ability to correctly estimate the unrooted
four-taxon tree. Maximum likelihood outperformed neighbor joining in 29 of
the 36 cases in which the assumptions of both methods were satisfied. In
133 of 180 of the simulations in which the assumptions of the
maximum-likelihood and neighbor-joining methods were violated, maximum
likelihood outperformed neighbor joining. These results are consistent with
a general superiority of maximum likelihood over neighbor joining under
comparable conditions. They extend and clarify an earlier study that found
an advantage for neighbor joining over maximum likelihood for
gamma-distributed mutation rates.
相似文献