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101.
Tannock GW Ghazally S Walter J Loach D Brooks H Cook G Surette M Simmers C Bremer P Dal Bello F Hertel C 《Applied and environmental microbiology》2005,71(12):8419-8425
The luxS gene of Lactobacillus reuteri 100-23C was amplified by PCR, cloned, and then sequenced. To define a physiological and ecological role for the luxS gene in L. reuteri 100-23C, a luxS mutant was constructed by insertional mutagenesis. The luxS mutant did not produce autoinducers AI-2 or AI-3. Complementation of the luxS mutation by a plasmid construct containing luxS restored AI-2 and AI-3 synthesis. In vitro experiments revealed that neither the growth rate, nor the cell yield, nor cell survival in the stationary phase were compromised in the luxS mutant relative to the wild type and complemented mutant. The ATP content of exponentially growing cells of the luxS mutant was, however, 65% of that of wild-type cells. Biofilms formed by the luxS mutant on plastic surfaces in a bioreactor were thicker than those formed by the wild type. Biofilm thickness was not restored to wild-type values by the addition of purified AI-2 to the culture medium. In vivo experiments, conducted with ex-Lactobacillus-free mice, showed that biofilms formed by the mutant strain on the epithelial surface of the forestomach were approximately twice as thick as those formed by the wild type. The ecological performance of the luxS mutant, when in competition with L. reuteri strain 100-93 in the mouse cecum, was reduced compared to that of a xylA mutant of 100-23C. These results demonstrate that LuxS influences important ecological attributes of L. reuteri 100-23C, the consequences of which are niche specific. 相似文献
102.
Liu H Tully DC Epple R Bursulaya B Li J Harris JL Williams JA Russo R Tumanut C Roberts MJ Alper PB He Y Karanewsky DS 《Bioorganic & medicinal chemistry letters》2005,15(22):4979-4984
A series of Nalpha-acyl-alpha-amino acid-(arylaminoethyl)amides were found to be potent and noncovalent cathepsin S inhibitors. Compound 20 possessed high cathepsin S affinity (Ki=3.3 nM) and showed excellent selectivity over cathepsin K, L, F, and V. Molecular modeling, design, synthesis, and in vitro activity are described. 相似文献
103.
Gaus H Olsen P Sooy KV Rentel C Turney B Walker KL McArdle JV Capaldi DC 《Bioorganic & medicinal chemistry letters》2005,15(18):4118-4124
Some commercial batches of dichloroacetic acid (DCA) contain traces of chloral (trichloroacetaldehyde). Using such DCA to effect detritylation during solid-phase oligonucleotide synthesis results in the formation of a family of process impurities in which the atoms of chloral (Cl3CCHO) are incorporated between the 5'-oxygen and phosphorus atoms of an internucleotide linkage. The structure was elucidated by HPLC with UV and MS detection, digestion of the oligonucleotide, synthesis of model compounds, and 1H and 31P NMR spectroscopy. By understanding the chemistry behind its formation, we are now able to limit levels of this impurity in synthetic oligonucleotides by limiting chloral in DCA. 相似文献
104.
105.
Stable isotope probing analysis of the influence of liming on root exudate utilization by soil microorganisms 总被引:3,自引:0,他引:3
Rangel-Castro JI Killham K Ostle N Nicol GW Anderson IC Scrimgeour CM Ineson P Meharg A Prosser JI 《Environmental microbiology》2005,7(6):828-838
Rhizosphere microorganisms play an important role in soil carbon flow, through turnover of root exudates, but there is little information on which organisms are actively involved or on the influence of environmental conditions on active communities. In this study, a 13CO2 pulse labelling field experiment was performed in an upland grassland soil, followed by RNA-stable isotope probing (SIP) analysis, to determine the effect of liming on the structure of the rhizosphere microbial community metabolizing root exudates. The lower limit of detection for SIP was determined in soil samples inoculated with a range of concentrations of 13C-labelled Pseudomonas fluorescens and was found to lie between 10(5) and 10(6) cells per gram of soil. The technique was capable of detecting microbial communities actively assimilating root exudates derived from recent photo-assimilate in the field. Denaturing gradient gel electrophoresis (DGGE) profiles of bacteria, archaea and fungi derived from fractions obtained from caesium trifluoroacetate (CsTFA) density gradient ultracentrifugation indicated that active communities in limed soils were more complex than those in unlimed soils and were more active in utilization of recently exuded 13C compounds. In limed soils, the majority of the community detected by standard RNA-DGGE analysis appeared to be utilizing root exudates. In unlimed soils, DGGE profiles from 12C and 13C RNA fractions differed, suggesting that a proportion of the active community was utilizing other sources of organic carbon. These differences may reflect differences in the amount of root exudation under the different conditions. 相似文献
106.
Yi EC Li XJ Cooke K Lee H Raught B Page A Aneliunas V Hieter P Goodlett DR Aebersold R 《Proteomics》2005,5(2):380-387
Quantitative protein profiling using the isotope-coded affinity tag (ICAT) method and tandem mass spectrometry (MS) enables the pair-wise comparison of protein expression levels in biological samples. A new version of the ICAT reagent with an acid-cleavable bond, which allows removal of the biotin moiety prior to MS and which utilizes (13)C substitution for (12)C in the heavy-ICAT reagent rather than (2)H (for (1)H) as in the original reagent, was investigated. We developed and validated an MS data acquisition strategy using this new reagent that results in an increased number of protein identifications per experiment, without losing the accuracy of protein quantification. This was achieved by following a single survey (precursor) ion scan and serial collision induced dissociations (CIDs) of four different precursor ions observed in the prior survey scan. This strategy is common to many high-performance liquid chromatography-electrospray ionization (HPLC-ESI)-MS shotgun proteomic strategies, but heretofore not to ICAT experiments. This advance is possible because the new ICAT reagent uses (13)C as the "heavy" element rather than (2)H, thus, eliminating the slight delay in retention time of ICAT-labeled "light" peptides on a C18-based HPLC separation that occurs with (2)H and (1)H. Analyses using this new scheme of an ICAT-labeled trypsin-digested six protein mixture as well as a tryptic digest of a total yeast lysate, indicated that about two times more proteins were identified in a single analysis, and that there was no loss in accuracy of quantification. 相似文献
107.
Orchard S Hermjakob H Taylor CF Potthast F Jones P Zhu W Julian RK Apweiler R 《Proteomics》2005,5(14):3552-3555
The spring workshop of the HUPO-PSI convened in Siena to further progress the data standards which are already making an impact on data exchange and deposition in the field of proteomics. Separate work groups pushed forward existing XML standards for the exchange of Molecular Interaction data (PSI-MI, MIF) and Mass Spectrometry data (PSI-MS, mzData) whilst significant progress was made on PSI-MS' mzIdent, which will allow the capture of data from analytical tools such as peak list search engines. A new focus for PSI (GPS, gel electrophoresis) was explored; as was the need for a common representation of protein modifications by all workers in the field of proteomics and beyond. All these efforts are contextualised by the work of the General Proteomics Standards workgroup; which in addition to the MIAPE reporting guidelines, is continually evolving an object model (PSI-OM) from which will be derived the general standard XML format for exchanging data between researchers, and for submission to repositories or journals. 相似文献
108.
Carrière Y Ellers-Kirk C Biggs R Degain B Holley D Yafuso C Evans P Dennehy TJ Tabashnik BE 《Journal of economic entomology》2005,98(3):947-954
Fitness costs associated with insect resistance to transgenic crops producing toxins from Bacillus thuringiensis (Bt) reduce the fitness on non-Bt refuge plants of resistant individuals relative to susceptible individuals. Because costs may vary among host plants, choosing refuge cultivars that increase the dominance or magnitude of costs could help to delay resistance. Specifically, cultivars with high concentrations of toxic phytochemicals could magnify costs. To test this hypothesis, we compared life history traits of three independent sets of pink bollworm, Pectinophora gossypiella (Saunders), populations on two cotton cultivars that differed in antibiosis against this cotton pest. Each set had an unselected susceptible population, a resistant population derived by selection from the susceptible population, and the F1 progeny of the susceptible and resistant populations. Confirming previous findings with pink bollworm feeding on cotton, costs primarily affected survival and were recessive on both cultivars. The magnitude of the survival cost did not differ between cultivars. Although the experimental results did not reveal differences between cultivars in the magnitude or dominance of costs, modeling results suggest that differences between cultivars in pink bollworm survival could affect resistance evolution. Thus, knowledge of the interaction between host plants and fitness costs associated with resistance to Bt crops could be helpful in guiding the choice of refuge cultivars. 相似文献
109.
Jonathan H. Epstein Jeffrey McKee Phil Shaw Vicki Hicks Gino Micalizzi Peter Daszak A. Marm Kilpatrick Gretchen Kaufman 《EcoHealth》2006,3(4):290-298
Over the last 20 years, Australian white ibis populations (Threskiornis molucca) have expanded into urban areas, leading to increased contact between ibis, domestic animals, and humans. This has led to
concern that ibis may transmit pathogens that threaten public health or food production. Here we report results from a study
of ibis viral serology and bacterial culture that indicate that ibis are hosts of zoonotic and livestock pathogens such as
Salmonella spp., Newcastle disease virus, avian influenza virus, and flaviviruses in Australia. We also performed a behavioral study
to measure contact rates among ibis, people, and livestock that determine the potential for disease transmission. 相似文献
110.
Yvonne J.K. Edwards Klaudia Walter Gayle McEwen Tanya Vavouri Krystyna A. Kelly Irina Abnizova Adam Woolfe Debbie K. Goode Martin Goodson Phil North Phil Snell Heather Callaway Sarah F. Smith Walter R. Gilks Julie E. Cooke Greg Elgar 《Comparative biochemistry and physiology. Part D, Genomics & proteomics》2006,1(1):46