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1.
Magni Olsen Kyrkjeeide Kristian Hassel Kjell Ivar Flatberg A. Jonathan Shaw Narjes Yousefi Hans K. Sten?ien 《PloS one》2016,11(2)
Spore-producing organisms have small dispersal units enabling them to become widespread across continents. However, barriers to gene flow and cryptic speciation may exist. The common, haploid peatmoss Sphagnum magellanicum occurs in both the Northern and Southern hemisphere, and is commonly used as a model in studies of peatland ecology and peatmoss physiology. Even though it will likely act as a rich source in functional genomics studies in years to come, surprisingly little is known about levels of genetic variability and structuring in this species. Here, we assess for the first time how genetic variation in S. magellanicum is spatially structured across its full distribution range (Northern Hemisphere and South America). The morphologically similar species S. alaskense was included for comparison. In total, 195 plants were genotyped at 15 microsatellite loci. Sequences from two plastid loci (trnG and trnL) were obtained from 30 samples. Our results show that S. alaskense and almost all plants of S. magellanicum in the northern Pacific area are diploids and share the same gene pool. Haploid plants occur in South America, Europe, eastern North America, western North America, and southern Asia, and five genetically differentiated groups with different distribution ranges were found. Our results indicate that S. magellanicum consists of several distinct genetic groups, seemingly with little or no gene flow among them. Noteworthy, the geographical separation of diploids and haploids is strikingly similar to patterns found within other haploid Sphagnum species spanning the Northern Hemisphere. Our results confirm a genetic division between the Beringian and the Atlantic that seems to be a general pattern in Sphagnum taxa. The pattern of strong genetic population structuring throughout the distribution range of morphologically similar plants need to be considered in future functional genomic studies of S. magellanicum. 相似文献
2.
Three local populations from Northeast Iceland are surveyed for the occurrence of the deflecting wrinkle of the metaconid on second deciduous and first permanent lower molars. The trait occurs more frequently on dm2 than on M1, and no sexual dimorphism is found, as expected. However, the frequencies are clearly within those predicted by the Mongoloid dental complex for Mongoloid populations. It is therefore suggested that the inclusion of the deflecting wrinkle in the Mongoloid dental complex be re-evaluated, and the racial diagnostic value of the trait taken with reservation. 相似文献
3.
Soluble guanylate cyclase enzyme was purified from human platelets. The soluble fraction of the lysed platelets was sequentially chromatographed over DEAE-sepharose, GTP-agarose and HPLC size-exclusion columns. About 0.1 mg of purified enzyme could be obtained from 2000 ml of platelet rich plasma. The purified enzyme had the specific activity of 205 nmoles cGMP/mg/min with Mn2+ as cofactor. The enzyme eluted at the 160,000 daltons position from the size-exclusion column. Electrophoresis in the presence of sodium dodecyl sulfate under reducing conditions revealed two subunits of 83,000 and 71,000 daltons respectively. 相似文献
4.
Ivar P. S. Agrell 《Cell and tissue research》1968,88(3):365-369
Summary Imaginal discs from developing larvae of the fly Calliphora erythrocephala fixed in permanganate or osmium tetroxide and embedded in Epon 812 were observed by electron microscopy. When the larval growth ceases, the differentiation manifests itself through an enlargement of the endoplasmic reticulum, by which continuous membrane contact is established between all cell organelles. During the same time mitochondria swell up and transform into lipid granules and the intercellular contacts weaken.I am indebted to Mrs Mariann Carleson and Miss Brita Nilsson for technical aid. 相似文献
5.
Productivity-diversity relationships for plants, bryophytes, lichens, and polypore fungi in six northern forest landscapes 总被引:1,自引:0,他引:1
Ivar Gjerde Magne Stersdal Jrund Rolstad Ken Olaf Storaunet Hans H. Blom Vegard Gundersen Einar Heegaard 《Ecography》2005,28(6):705-720
We investigated the relationship between site productivity and diversity of vascular plants, bryophytes, lichens, and polypore fungi in forests based on species richness data in 0.25 ha forest plots (grain size), selected from six 150–200 ha study areas (focus), and spanning over a latitudinal distance of 1350 km (extent) in Norway. We 1) searched for prevailing productivity-diversity relationships (PDRs), 2) compared PDRs among taxonomic groups and species found in different micro-habitats, and 3) investigated the effect of increasing plot (grain) size on PDRs. Using vegetation types as a surrogate for site productivity, we found a general pattern of increasing species richness with site productivity. On average total species richness doubled with a ten-fold increase in productivity. Lichens PDRs stood out as less pronounced and more variable than for other species groups investigated. PDRs of species associated with downed logs tended to level off at high-productive sites, a pattern interpreted as an effect of disturbance. Increasing the grain size >10-fold did not change the proportional difference in species richness between sites with high and low productivity. 相似文献
6.
T Wadstr?m K Andersson M Sydow L Axelsson S Lindgren B Gullmar 《The Journal of applied bacteriology》1987,62(6):513-520
One hundred wild-type strains of the genus Lactobacillus were isolated from the small intestine of newly-slaughtered pigs up to 6 months of age. Cell surface hydrophobicity and capsule formation were studied on a number of strains. Strains showing high surface hydrophobicity as measured by the salt-aggregation test and hydrophobic interaction chromatography on Octyl Sepharose were commonly found to adhere in high numbers to isolated pig intestinal epithelial cells. Heat and protease treatment of bacteria of high surface hydrophobicity, including autoaggregating strains in phosphate-buffered saline, showed a drastic decline in this surface property. Three hydrophilic strains (LBp 1044, 1068 and 1073) also showed binding to intestinal cells but at a lower level (approx. 5 bacteria/cell) as compared with the best binding hydrophobic strain (LBp 1063, approx. 11 bacteria/cell). These findings suggest that different or multiple adhesion mechanisms may be involved in the colonization of the small intestinal mucosa of pigs. Cultures of selected strains grown in liquid media rich in carbohydrates did not affect their hydrophobic cell surface character. Therefore it seems less likely that carbohydrate capsule polymers are the major determinants of intestinal colonization of lactobacilli in pigs. 相似文献
7.
Characterization and DNA homology of Lactobacillus strains isolated from pig intestine 总被引:4,自引:0,他引:4
Twenty strains of the genus Lactobacillus were isolated from pig intestines and characterized with phenotypic tests. Eleven of these strains, together with selected reference strains, were subjected to DNA homology studies. Three major groups could be distinguished by biochemical/physiological tests and by DNA homology studies: one homofermentative group of the subgenus Thermobacterium and two heterofermentative groups. The DNA homology studies revealed that strains from the homofermentative group were related to Lactobacillus acidophilus strain VPI 1754, but showed a low relationship to the type strain of Lact. acidophilus. One One group of the heterofermentative strains was related to the type strain of Lact. reuteri; the other group, consisting of three strains, showed a low relationship to all reference strains used. These three strains had the unusual property of producing succinic acid in large amounts. 相似文献
8.
Summary C-band polymorphisms of chromosome 1 can be quantified by Ce bands visualized using oblique epi-illumination. In this paper the polymorphic region of chromosome 9, including variants such as 9qh+, inversions, and translocations, was analyzed in a total of 1860 chromosomes from 20 individuals and 8 fetuses. In this sample we found between zero and five Ce bands on 9q and between zero and four Ce bands on 9p with a maximum of five Ce bands per chromosome. On the basis of these observations at least 19 different polymorphic patterns can be expected theoretically, 15 of which were observed in our sample. Among these, five polymorphic Ce-band classes were distinguishable by the method presented. Considering both homologues, 52=25 quantitatively discernible chromosome 9 pairs may exist. 相似文献
9.
A general procedure has been given previously for calculating frequencies of the morphs Long, Mid, and Short in equilibrium populations of tristylous plants. It is now demonstrated that an equilibrium state actually exists at the genotype level if this procedure produces admissible morph frequencies. This result holds in a diploid model, with or without linkage between the two loci involved. It is shown how the genotype frequencies may be determined for any set of mating probabilities. It is also explained how these frequencies may be calculated in a tetraploid model incorporating double reduction. The general theory is applied to a particular situation where the Mid morph is at a selective disadvantage as a seed parent. 相似文献
10.
Ivar P. S. Agrell 《Cell and tissue research》1966,72(1):22-29
Summary Imaginal discs from mature larvae of the fly Calliphora erythrocephala fixed in permanganate and embedded in Epon 812 were observed by electron microscopy. Irrespective of the type of the disc, the endoplasmic reticulum in the cells was found to be in unbroken contact with the outer nuclear membrane, Golgi areas, the mitochondria and the cell membrane. The imaginai discs are syncytial in that all cells are in cytoplasmic communication through secondary breaks in the cell membranes.The investigation was facilitated by grants from the Nordic Insulin Foundation.I am indebted to Mrs. Mariann Carleson and Miss Brita Nilsson for technical aid. 相似文献