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51.
The phylogenetic position of the archaebacteria and the place of eukaryotes
in the history of life remain a question of debate. Recent studies based on
some protein-sequence data have obtained unusual phylogenies for these
organisms. We therefore collected the protein sequences that were available
with representatives from each of the major forms of life: the
gram-negative bacteria, gram-positive bacteria, archaebacteria, and
eukaryotes. Monophyletic, unrooted phylogenies based on these sequence data
show that seven of 24 proteins yield a significant
gram-positive-archaebacteria clade/gram-negative- eukaryotic clade. The
phylogenies for these seven proteins cannot be explained by the traditional
three-way split of the eukaryotes, archaebacteria, and eubacteria. Nine of
the 24 proteins yield the traditional gram-positive-gram-negative
clade/archaebacteria-eukaryotic clade. The remaining eight proteins give
phylogenies that cannot be statistically distinguished. These results
support the hypothesis of a chimeric origin for the eukaryotic cell nucleus
formed from the fusion of an archaebacteria and a gram-negative bacteria.
相似文献
52.
C. DARRIN HULSEY PHILLIP R. HOLLINGSWORTH JR ROI HOLZMAN 《Biological journal of the Linnean Society. Linnean Society of London》2010,100(3):619-629
The ability of Perciform fishes to protrude their jaw has likely been critical to the trophic diversification of this group, which includes approximately 20% of all vertebrates. The length of the ascending process of the premaxilla is thought to influence the maximum extent that cichlids and other Perciforms protrude their oral jaw. Using a combination of morphometrics, kinematics, and new phylogenetic hypotheses for 20 Heroine cichlid species, we tested the evolutionary relationship between the length of the premaxillary ascending process and maximum jaw protrusion. In this clade, the length of the ascending process of the premaxilla ranged from 11.6–32.7% with respect to standard length whereas maximum jaw protrusion ranged from 3.5–23.4% with respect to standard length. The evolutionary relationships among the Heroine cichlids obtained from the genetic partitions cytochrome b, S7, and RAG1 showed limited concordance. However, correlations between the length of the ascending process and maximum jaw protrusion were highly significant when examined as independent contrasts using all three topologies. Evolutionary change in the length of the ascending process of the premaxilla is likely critical for determining the amount of jaw protrusion in Perciform groups such as cichlid fishes. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 619–629. 相似文献
53.
Background
We recently observed an association of resistance with a certain enteropathogenic Escherichia coli (EPEC) serotypes and identified a conjugative plasmid, similar to plasmid pED208, that was conserved among archival O111:H2/NM and O119:H2 strains of diverse geographical origin. In this study, we sought to determine the prevalence and distribution of this plasmid among a collection of EPEC isolates from Brazil, as well as to study the susceptibilities of these isolates to antimicrobial agents. 相似文献54.
S. Nishanth Kumar C Mohandas Bala Nambisan RS Sreerag CA Jayaprakas 《Folia microbiologica》2014,59(3):197-202
In continuation of our search for new antimicrobial secondary metabolites from Bacillus cereus associated with rhabditid entomopathogenic nematode, a new microbial diketopiperazine, cyclo(l-Pro-d-Arg), was isolated from the ethyl acetate extract of fermented modified nutrient broth. The chemical structures of the isolated compounds were identified based on their 1D, 2D NMR and high-resolution electrospray ionisation–mass spectroscopy data. Antibacterial activity of the compound was determined by minimum inhibitory concentration and disc diffusion method against medically important bacteria, and the compound was recorded to have significant antibacterial activity against test bacteria. The highest activity was recorded against Klebsiella pneumoniae (1 μg/mL). Cyclo(l-Pro-d-Arg) was recorded to have significant antitumor activity against HeLa cells (IC50 value 50 μg/mL), and this compound was recorded to have no cytotoxicity against normal monkey kidney cells (VERO) up to 100 μg/mL). To the best of our knowledge, this is the first time that cyclo(l-Pro-d-Arg) has been isolated from a microbial natural source. 相似文献
55.
We used immunohistochemistry to quantify and compare the expression of Toll-like receptor 2 (TLR2) and cluster of differentiation 14 (CD14) in gingival tissues of both healthy individuals and patients with chronic periodontitis. We also correlated the expression of TLR2 and CD14 with the histological grades of chronic periodontitis. We examined 30 gingival specimens from chronic periodontitis patients and 10 from healthy individuals. Tissues from both groups were immunostained with antibodies against TLR2 and CD14. TLR2 and CD14 were expressed by endothelial cells, fibroblasts, lymphocytes and plasma cells. The immunohistochemical expression of TLR2 and CD14 was significantly greater in inflammatory cells of the chronic periodontitis group than in healthy individuals. Expression of these molecules was greater in the inflammatory cells of connective tissue adjacent to pocket epithelium in both groups. The expression of TLR2 and CD14 was greatest in the periodontitis group that was classified as severe grade, followed by moderate and mild grades, which suggests a role of TLR2 and CD14 in the pathogenesis of chronic periodontitis. The positive correlation of TLR2 and CD14 expression levels with the severity grades of chronic periodontitis suggests that they are correlated also with disease severity; therefore, they may be useful for predicting disease progression. Our findings are consistent with the possibility that CD14 acts as a co-receptor for TLR2. 相似文献
56.
AAM Coelho-Castelo AP Trombone RS Rosada RR Santos Jr VLD Bonato A Sartori CL Silva 《Genetic vaccines and therapy》2006,4(1):1-10
In order to assess a new strategy of DNA vaccine for a more complete understanding of its action in immune response, it is important to determine the in vivo biodistribution fate and antigen expression. In previous studies, our group focused on the prophylactic and therapeutic use of a plasmid DNA encoding the Mycobacterium leprae 65-kDa heat shock protein (Hsp65) and achieved an efficient immune response induction as well as protection against virulent M. tuberculosis challenge. In the present study, we examined in vivo tissue distribution of naked DNA-Hsp65 vaccine, the Hsp65 message, genome integration and methylation status of plasmid DNA. The DNA-Hsp65 was detectable in several tissue types, indicating that DNA-Hsp65 disseminates widely throughout the body. The biodistribution was dose-dependent. In contrast, RT-PCR detected the Hsp65 message for at least 15 days in muscle or liver tissue from immunized mice. We also analyzed the methylation status and integration of the injected plasmid DNA into the host cellular genome. The bacterial methylation pattern persisted for at least 6 months, indicating that the plasmid DNA-Hsp65 does not replicate in mammalian tissue, and Southern blot analysis showed that plasmid DNA was not integrated. These results have important implications for the use of DNA-Hsp65 vaccine in a clinical setting and open new perspectives for DNA vaccines and new considerations about the inoculation site and delivery system. 相似文献
57.
Mitochondrial DNA variation and genetic structure in populations of Drosophila melanogaster 总被引:5,自引:0,他引:5
The understanding of the genetic structure of a species can be improved by
considering together data from different types of genetic markers. In the
past, a number of worldwide populations of Drosophila melanogaster have
been extensively studied for several such markers, including allozymes,
chromosomal inversions, and quantitative characters. Here we present
results from a study of restriction- fragment-length polymorphisms of
mitochondrial DNA (mtDNA) in 92 isofemale lines from many of the same
geographic populations of D. melanogaster. Eleven restriction enzymes were
used, of which four revealed restriction-site polymorphism. A total of 24
different haplotypes were observed, of which 18 were unique to single
populations. In many populations, the unique haplotypes have reached high
frequency without being observed in neighboring populations. A Wagner
parsimony tree reveals that mutationally close variants show geographical
clumping, suggesting local differentiation of mtDNA in populations. The
Old-World and the New-World populations are differentiated, with the
predominant Old-World haplotype being virtually absent from the New World.
These results contrast with those for the nuclear genes, in which many loci
show parallel clines in different continents, and suggest a common origin
of D. melanogaster populations in North America.
相似文献
58.