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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.
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C. G. Flocco A. Lobalbo M. P. Carranza M. Bassi A. M. Giulietti W. P. Mac Cormack 《International journal of phytoremediation》2002,4(3):169-186
Alfalfa (Medicago sativa L.) and other plants bearing an important root system have been shown to be effective in the removal of organic compounds, including polycyclic aromatic hydrocarbons (PAHs). Phenanthrene is one of the main contaminants arising from the petrochemical industry and is included in the USEPA's list of priority toxic pollutants. Hydroponic cultures of alfalfa were employed as a model system to evaluate their capability of removing phenanthrene and to study the plant-pollutant interaction without the interference of a soil matrix. The removal of phenanthrene was followed over a period of 30 days. The half-life of phenanthrene in hydroponics (initial concentration 50 mg L-1) was reduced 2.7 times when plants were present. Growth index, chlorophyll content of leaves, and peroxidase activity of the roots of plants exposed to phenanthrene were lower than the corresponding values of nonexposed plants. Phenanthrene produced an acute negative effect on the total bacterial counts but also caused an increase in degraders/total bacteria ratio. The Ames Salmonella plate incorporation assay was employed to screen for potential genotoxic metabolites, which could be generated by metabolic activation of the parent compound. None of the samples exhibited a positive response. While lack of a positive response to this test is not a definitive evidence of the absence of genotoxic substances, these results suggest that the plant-assisted removal of phenanthrene merits further investigation. 相似文献
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Summary The heterotrophic bacterial flora of Antarctic fish Notothenia neglecta was studied in Potter Cove (King George Island, South Shetland Islands). Quantitative and qualitative analysis of aerobic bacteria from sea water, skin, stomach and intestine were carried out. In addition, anaerobic flora of stomach and intestine was studied and compared. Pseudomonas was dominant in sea water samples but, neither skin nor digestive tract samples showed to be rich in this genus. Stomach flora showed variable results between samples. The gut flora was composed almost exclusively of Vibrio. Despite extreme environmental conditions this Antarctic fish show an intestinal indigenous microflora very similar to warmer waters fish. Several factors, that we discussed, could be determining the Vibrio dominance in the gut of marine teleosts. 相似文献