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81.
The culturability of three Campylobacter jejuni strains and their infectivity for day-old chicks were assessed following storage of the strains in saline. The potential for colonization of chicks was weakened during the storage period and terminated 3 to 4 weeks before the strains became nonculturable. The results from this study suggest that the role of starved and aged but still culturable campylobacters may be diminutive, but even more, that the role of viable but nonculturable stages in campylobacter epidemiology may be negligible. Even high levels of maternally derived anti-campylobacter outer membrane protein serum antibodies in day-old chicks did not protect the chicks from campylobacter colonization. 相似文献
82.
Molecular phylogeny of living xenarthrans and the impact of character and taxon sampling on the placental tree rooting 总被引:14,自引:0,他引:14
Delsuc F Scally M Madsen O Stanhope MJ de Jong WW Catzeflis FM Springer MS Douzery EJ 《Molecular biology and evolution》2002,19(10):1656-1671
Extant xenarthrans (armadillos, anteaters and sloths) are among the most derived placental mammals ever evolved. South America was the cradle of their evolutionary history. During the Tertiary, xenarthrans experienced an extraordinary radiation, whereas South America remained isolated from other continents. The 13 living genera are relics of this earlier diversification and represent one of the four major clades of placental mammals. Sequences of the three independent protein-coding nuclear markers alpha2B adrenergic receptor (ADRA2B), breast cancer susceptibility (BRCA1), and von Willebrand Factor (VWF) were determined for 12 of the 13 living xenarthran genera. Comparative evolutionary dynamics of these nuclear exons using a likelihood framework revealed contrasting patterns of molecular evolution. All codon positions of BRCA1 were shown to evolve in a strikingly similar manner, and third codon positions appeared less saturated within placentals than those of ADRA2B and VWF. Maximum likelihood and Bayesian phylogenetic analyses of a 47 placental taxa data set rooted by three marsupial outgroups resolved the phylogeny of Xenarthra with some evidence for two radiation events in armadillos and provided a strongly supported picture of placental interordinal relationships. This topology was fully compatible with recent studies, dividing placentals into the Southern Hemisphere clades Afrotheria and Xenarthra and a monophyletic Northern Hemisphere clade (Boreoeutheria) composed of Laurasiatheria and Euarchontoglires. Partitioned likelihood statistical tests of the position of the root, under different character partition schemes, identified three almost equally likely hypotheses for early placental divergences: a basal Afrotheria, an Afrotheria + Xenarthra clade, or a basal Xenarthra (Epitheria hypothesis). We took advantage of the extensive sampling realized within Xenarthra to assess its impact on the location of the root on the placental tree. By resampling taxa within Xenarthra, the conservative Shimodaira-Hasegawa likelihood-based test of alternative topologies was shown to be sensitive to both character and taxon sampling. 相似文献
83.
Sexual dimorphism in lizard body shape: the roles of sexual selection and fecundity selection 总被引:5,自引:0,他引:5
Olsson M Shine R Wapstra E Uivari B Madsen T 《Evolution; international journal of organic evolution》2002,56(7):1538-1542
Sexual dimorphism is widespread in lizards, with the most consistently dimorphic traits being head size (males have larger heads) and trunk length (the distance between the front and hind legs is greater in females). These dimorphisms have generally been interpreted as follows: (1) large heads in males evolve through male-male rivalry (sexual selection); and (2) larger interlimb lengths in females provide space for more eggs (fecundity selection). In an Australian lizard (the snow skink, Niveoscincus microlepidotus), we found no evidence for ongoing selection on head size. Trunk length, however, was under positive fecundity selection in females and under negative sexual selection in males. Thus, fecundity selection and sexual selection work in concert to drive the evolution of sexual dimorphism in trunk length in snow skinks. 相似文献
84.
85.
Jensen GB Larsen P Jacobsen BL Madsen B Smidt L Andrup L 《Applied and environmental microbiology》2002,68(10):4900-4905
In a study of occupational exposure to Bacillus thuringiensis, 20 exposed greenhouse workers were examined for Bacillus cereus-like bacteria in fecal samples and on biomonitoring filters. Bacteria with the following characteristics were isolated from eight individuals: intracellular crystalline inclusions characteristic of B. thuringiensis, genes for and production of B. cereus enterotoxins, and positivity for cry11 as determined by PCR. DNA fingerprints of the fecal isolates were identical to those of strains isolated from the commercial products used. Work processes (i.e., spraying) correlated with the presence of B. thuringiensis in the fecal samples (10(2) to 10(3) CFU/g of feces). However, no gastrointestinal symptoms correlated with the presence of B. thuringiensis in the fecal samples. 相似文献
86.
Bakermans C Hohnstock-Ashe AM Padmanabhan S Padmanabhan P Madsen EL 《Microbial ecology》2002,44(2):107-117
We used geochemical analyses of groundwater and laboratory-incubated microcosms to investigate the physiological responses
of naturally occurring microorganisms to coal-tar-waste constituents in a contaminated aquifer. Waters were sampled from wells
along a natural hydrologic gradient extending from uncontaminated (1 well) into contaminated (3 wells) zones. Groundwater
analyses determined the concentrations of carbon and energy sources (pollutants or total organic carbon), final electron acceptors
(oxygen, nitrate, sulfate), and metabolic byproducts (dissolved inorganic carbon [DIC], alkalinity, methane, ferrous iron,
sulfide, Mn2+). In the contaminated zone of the study site, concentrations of methane, hydrogen, alkalinity, and DIC were
enhanced, while dissolved oxygen and nitrate were depleted. Field-initiated biodegradation assays using headspace-free serum
bottle microcosms filled with groundwater examined metabolism of the ambient organic contaminants (naphthalene, 2-methylnaphthalene,
benzothiophene, and indene) by the native microbial communities. Unamended microcosms from the contaminated zone demonstrated
the simultaneous degradation of several coal-tar-waste constituents at the in situ temperature (10°C). Lag phases prior to
the onset of biodegradation indicated the prevalence of both aerobic and anaerobic conditions in situ. Electron acceptor-amended
microcosms from the most contaminated well waters demonstrated only aerobic naphthalene degradation. Collectively, the geochemical
and microbial evidence show that biodegradation of coal-tar-waste constituents occurs via both aerobic and anaerobic terminal
electron accepting processes at this site. 相似文献
87.
Glenting J Madsen SM Vrang A Fomsgaard A Israelsen H 《Applied and environmental microbiology》2002,68(10):5051-5056
We report the development of a nonantibiotic and nonpathogenic host-plasmid selection system based on lactococcal genes and threonine complementation. We constructed an auxotrophic Lactococcus lactis MG1363Deltathr strain which carries deletions in two genes encoding threonine biosynthetic enzymes. To achieve plasmid-borne complementation, we then constructed the minimal cloning vector, pJAG5, based on the genes encoding homoserine dehydrogenase-homoserine kinase (the hom-thrB operon) as a selective marker. Using strain MG1363Deltathr, selection and maintenance of cells carrying pJAG5 were obtained in threonine-free defined media. Compared to the commonly used selection system based on erythromycin resistance, the designed complementation system offers a competitive and stable plasmid selection system for the production of heterologous proteins in L. lactis. The potential of pJAG5 to deliver genes for expression in eukaryotes was evaluated by insertion of a mammalian expression unit encoding a modified green fluorescent protein. The successful delivery and expression of genes in human kidney fibroblasts indicated the potential of the designed nonantibiotic host-plasmid system for use in genetic immunization. 相似文献
88.
Tipsmark CK Madsen SS Seidelin M Christensen AS Cutler CP Cramb G 《The Journal of experimental zoology》2002,293(2):106-118
89.
Madsen B Spencer-Dene B Poulsom R Hall D Lu PJ Scott K Shaw AT Burchell JM Freemont P Taylor-Papadimitriou J 《Mechanisms of development》2002,119(Z1):S239-S246
90.
Bohle DS Kosar AD Madsen SK 《Biochemical and biophysical research communications》2002,294(1):132-135
Malaria pigment, or beta-hematin, the insoluble heme detoxification product resulting from the intraerythrocitic digestion of hemoglobin by young malaria trophozoites has been structurally characterized by X-ray powder diffraction and shown to contain chains of propionic acid linked dimers. Although there is considerable spectroscopic evidence for a monodentate propionate-iron interaction in this crystalline material, the spectroscopic characterization of the propionic acid dimer is limited. Herein we demonstrate the presence of the propionic acid dimer unit by H/D isotope substitution in carboxylic acid dimer. In the Raman spectrum of the deuterium substituted compound there is a circa 12 cm(-1) shift, H: 1629 cm(-1) vs. D: 1617 cm(-1) in the symmetric ring breathing mode for the propionic acid dimer. On the other hand, the IR active asymmetric stretch has a very small shift, <3 cm(-1), upon deuteration. These, and other vibrational data, are consistent with the presence of a planar carboxylic acid dimer in the structure of beta-hematin. 相似文献