Swedish University of Agricultural Sciences

About: Swedish University of Agricultural Sciences is a education organization based out in Uppsala, Sweden. It is known for research contribution in the topics: Population & Soil water. The organization has 13510 authors who have published 35241 publications receiving 1414458 citations. The organization is also known as: Sveriges Lantbruksuniversitet & SLU.

Extinction thresholds and disrupted plant-pollinator interactions in fragmented plant populations

Abstract: In order to estimate how much population extinction risk may be affected by local fragmentation, population viability analyses were performed in six populations of the endangered grassland herb Gentianella campestris in Sweden. The populations had been experimentally reintroduced to grasslands that were locally fragmented by juniper shrubs. The sites represented three sizes of grassland and two levels of grassland abundance in the landscape. Five years' demographic data were evaluated in a stochastic matrix population model, and studies of seed set, pollinator abundance, and inbreeding depression were performed in order to examine possible links between population viability and pollination. In all six sites, plants with reduced capacity of self-pollination (due to herkogamy) showed strongly reduced population viability in locally fragmented grassland habit, with pronounced extinction thresholds at certain levels of local fragmentation. Population viability was reduced because of inbreeding depression and reduced seed production in combination, both caused by pollinator deficit in locally fragmented grasslands. Plants with high selfing capacity had low population viability over the entire local fragmentation gradients. Selfing yielded high seed set in the absence of pollinators and was advantageous in fragmented parts of the grasslands. However, selfing had negative effects in nonfragmented parts of the grasslands, because it decreased the chances of cross-pollination and because selfed progeny had reduced fitness compared to outcrossed offspring. A comparison among the six sites indicated that the negative effects of local fragmentation were amplified by reduced size of the grassland sites and by reduced abundance of grassland habitat in the landscape. To my knowledge, this is the first quantitative estimate of increased extinction risk in fragmented plant populations.

Removal of antibiotic resistance gene-carrying plasmids from Lactobacillus reuteri ATCC 55730 and characterization of the resulting daughter strain, L. reuteri DSM 17938.

Abstract: The spread of antibiotic resistance in pathogens is primarily a consequence of the indiscriminate use of antibiotics, but there is concern that food-borne lactic acid bacteria may act as reservoirs of antibiotic resistance genes when distributed in large doses to the gastrointestinal tract. Lactobacillus reuteri ATCC 55730 is a commercially available probiotic strain which has been found to harbor potentially transferable resistance genes. The aims of this study were to define the location and nature of β-lactam, tetracycline, and lincosamide resistance determinants and, if they were found to be acquired, attempt to remove them from the strain by methods that do not genetically modify the organism before subsequently testing whether the probiotic characteristics were retained. No known β-lactam resistance genes was found, but penicillin-binding proteins from ATCC 55730, two additional resistant strains, and three sensitive strains of L. reuteri were sequenced and comparatively analyzed. The β-lactam resistance in ATCC 55730 is probably caused by a number of alterations in the corresponding genes and can be regarded as not transferable. The strain was found to harbor two plasmids carrying tet(W) tetracycline and lnu(A) lincosamide resistance genes, respectively. A new daughter strain, L. reuteri DSM 17938, was derived from ATCC 55730 by removal of the two plasmids, and it was shown to have lost the resistances associated with them. Direct comparison of the parent and daughter strains for a series of in vitro properties and in a human clinical trial confirmed the retained probiotic properties of the daughter strain.

New views on RPE65 deficiency: the rod system is the source of vision in a mouse model of Leber congenital amaurosis.

Abstract: Leber congenital amaurosis (LCA) is the most serious form of the autosomal recessive childhood-onset retinal dystrophies. Mutations in the gene encoding RPE65, a protein vital for regeneration of the visual pigment rhodopsin in the retinal pigment epithelium1, account for 10–15% of LCA cases2,3. Whereas previous studies of RPE65 deficiency in both animal models1,4 and patients5,6 attributed remaining visual function to cones, we show here that light-evoked retinal responses in fact originate from rods. For this purpose, we selectively impaired either rod or cone function in Rpe65−/− mice by generating double– mutant mice with models of pure cone function7 (rhodopsin-deficient mice; Rho−/−) and pure rod function8 (cyclic nucleotide–gated channel α3–deficient mice; Cnga3−/−). The electroretinograms (ERGs) of Rpe65−/− and Rpe65−/−Cnga3−/− mice were almost identical, whereas there was no assessable response in Rpe65−/−Rho−/− mice. Thus, we conclude that the rod system is the source of vision in RPE65 deficiency. Furthermore, we found that lack of RPE65 enables rods to mimic cone function by responding under normally cone-isolating lighting conditions. We propose as a mechanism decreased rod sensitivity due to a reduction in rhodopsin content to less than 1%. In general, the dissection of pathophysiological processes in animal models through the introduction of additional, selective mutations is a promising concept in functional genetics.