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1.
Summary The use of reticulated polyurethane foam as a support material for the immobilization of methanogenic associations and its application to the anaerobic treatment of fine particulate solid wastes was investigated. The colonization of polyurethane support particles in a continuous upflow reactor fed on a mixture of acetate, propionate and butyrate, was both rapid and dense. The combination of rumen microorganisms and colonized support particles in a two-phase digester resulted in an efficient anaerobic decomposition of papermill sludge. 相似文献
2.
Defense mechanisms of conifers : differences in constitutive and wound-induced monoterpene biosynthesis among species 总被引:7,自引:0,他引:7 下载免费PDF全文
Levels of monoterpene cyclase activity were determined in extracts from wounded and unwounded saplings of 10 conifer species to assess whether oleoresin biosynthesis is induced by stem wounding. Species of Abies and Picea, with low to moderate levels of constitutive monoterpene cyclase activity, exhibited a five- to 15-fold increase in cyclase activity 7 days after wounding relative to unwounded controls. In contrast, species of genera such as Pinus, with high levels of constitutive cyclase activity, did not significantly respond to wounding by alteration in the level of cyclase activity. The highest fold increase in monoterpene cyclase activity was consistently observed in Abies grandis, and the time-course of induction of activity following stem wounding in this species demonstrated a threefold increase at 2 days relative to unwounded controls, rising to a maximum increase in the response at 9 days (greater than 10-fold) followed by an apparent decline. The wound response was localized, and both bark (phloem) and wood (xylem) tissues displayed increased cyclase activity at the wound site. The magnitude of the increase in cyclase activity was dependent on the severity of the wound. 相似文献
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4.
Contribution of anaerobic protozoa and methanogens to hindgut metabolic activities of the American cockroach, Periplaneta americana. 总被引:2,自引:1,他引:1 下载免费PDF全文
The ciliate Nyctotherus ovalis occurs in high numbers in the hindgut of the American cockroach (Periplaneta americana) and harbors methanogenic bacteria as endosymbionts. The contribution of these hindgut microorganisms to metabolic and developmental processes of P. americana was studied by comparing cultures of cockroaches in which the composition of the hindgut microbial population was altered in various ways. Rearing the insects protozoan free resulted in increased insect generation time, decreased adult body weight, and absence of methane production. After feeding of protozoan-free adult cockroaches with a hindgut suspension containing N. ovalis and methanogens, methane increased to normal values and insect body weight was restored during the development of the second generation of insects. Feeding the protozoan-free cockroaches a hindgut suspension which was made free of N. ovalis resulted in an increase in methane production to only about 20% of the normal methane production level. This suggests that the methanogenic endosymbionts of N. ovalis are the major source of methane production in the hindgut. Inhibition of methanogens by addition of bromoethanesulfonic acid to the drinking water of a normal cockroach culture resulted in a reduction of methane production to about 2% of the normal level. No effects on insect body weight or the number of N. ovalis organisms were observed, but the fermentation pattern in the hindgut was shifted towards a relative increase in propionate levels. Similar results were obtained for in vitro cultures of hindgut microorganisms treated with bromoethanesulfonic acid. The results suggest a major role for hindgut protozoa in cockroach metabolic activities, especially during the insect growth period. The relatively large amounts of methane produced by cockroaches and by other methane-producing xylophagous insects suggest a major contribution by insects to global methane production. 相似文献
5.
Soybean Seed Coat Peroxidase (A Comparison of High-Activity and Low-Activity Genotypes) 总被引:2,自引:0,他引:2 下载免费PDF全文
Peroxidase activity in the seed coats of soybean (Glycine max [L.] Merr.) is controlled by the Ep locus. We compared peroxidase activity in cell-free extracts from seed coat, root, and leaf tissues of three EpEp cultivars (Harosoy 63, Harovinton, and Coles) to three epep cultivars (Steele, Marathon, and Raiden). Extracts from the seed coats of EpEp cultivars were 100-fold higher in specific activity than those from epep cultivars, but there was no difference in specific activity in crude root or leaf extracts. Isoelectric focusing of root tissue extracts and staining for peroxidase activity showed that EpEp cultivars had a root peroxidase of identical isoelectric point to the seed coat peroxidase, whereas roots of the epep types were lacking that peroxidase, indicating that the Ep locus may also affect expression in the root. In seed coat extracts, peroxidase was the most abundant soluble protein in EpEp cultivars, whereas this enzyme was present only in trace amounts in epep genotypes, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Histochemical localization of peroxidase activity in seed coats of EpEp cultivars shows that the enzyme occurs predominately in the cytoplasm of hourglass cells of the subepidermis. No obvious difference in the gross or microscopic structure of the seed coat was observed to be associated with the Ep locus. These results suggest that soybean seed coat peroxidase may be involved in processes other than seed coat biosynthesis. 相似文献
6.
Oleoresinosis in Grand Fir (Abies grandis) Saplings and Mature Trees (Modulation of this Wound Response by Light and Water Stresses) 总被引:3,自引:1,他引:2 下载免费PDF全文
The stem content of diterpene resin acids (rosin) increases dramatically following wounding of grand fir (Abies grandis) saplings, but the level of monoterpene olefins (turpentine) in the stem decreases following injury, in spite of a significant increase in monoterpene cyclase (synthase) activity. However, this observation was explained when rapid evaporative losses of the volatile monoterpenes from the wound site was demonstrated by trapping experiments, a finding consistent with a role of turpentine as a solvent for the mobilization and deposition of rosin to seal the injury. Mature forest trees responded to stem wounding by the enhancement of monoterpene cyclization capacity in a manner similar to 2-year-old grand fir saplings raised in the greenhouse. Light and water stresses greatly reduced the constitutive level of monoterpene cyclase activity and abolished the wound-induced response. The diminution in monoterpene biosynthetic capacity was correlated with a dramatic decrease in cyclase protein as demonstrated by immunoblotting. Relief of stress conditions resulted in the restoration of cyclase activity (both constitutive and wound induced) to control levels. The results of these experiments indicate that grand fir saplings are a suitable model for studies of the regulation of defensive oleoresinosis in conifers. 相似文献
7.
Background
Long-term benefits in animal breeding programs require that increases in genetic merit be balanced with the need to maintain diversity (lost due to inbreeding). This can be achieved by using optimal contribution selection. The availability of high-density DNA marker information enables the incorporation of genomic data into optimal contribution selection but this raises the question about how this information affects the balance between genetic merit and diversity.Methods
The effect of using genomic information in optimal contribution selection was examined based on simulated and real data on dairy bulls. We compared the genetic merit of selected animals at various levels of co-ancestry restrictions when using estimated breeding values based on parent average, genomic or progeny test information. Furthermore, we estimated the proportion of variation in estimated breeding values that is due to within-family differences.Results
Optimal selection on genomic estimated breeding values increased genetic gain. Genetic merit was further increased using genomic rather than pedigree-based measures of co-ancestry under an inbreeding restriction policy. Using genomic instead of pedigree relationships to restrict inbreeding had a significant effect only when the population consisted of many large full-sib families; with a half-sib family structure, no difference was observed. In real data from dairy bulls, optimal contribution selection based on genomic estimated breeding values allowed for additional improvements in genetic merit at low to moderate inbreeding levels. Genomic estimated breeding values were more accurate and showed more within-family variation than parent average breeding values; for genomic estimated breeding values, 30 to 40% of the variation was due to within-family differences. Finally, there was no difference between constraining inbreeding via pedigree or genomic relationships in the real data.Conclusions
The use of genomic estimated breeding values increased genetic gain in optimal contribution selection. Genomic estimated breeding values were more accurate and showed more within-family variation, which led to higher genetic gains for the same restriction on inbreeding. Using genomic relationships to restrict inbreeding provided no additional gain, except in the case of very large full-sib families. 相似文献8.
9.
Background
Gene loss, inversions, translocations, and other chromosomal rearrangements vary among species, resulting in different rates of structural genome evolution. Major chromosomal rearrangements are rare in most eukaryotes, giving large regions with the same genes in the same order and orientation across species. These regions of macrosynteny have been very useful for locating homologous genes in different species and to guide the assembly of genome sequences. Previous analyses in the fungi have indicated that macrosynteny is rare; instead, comparisons across species show no synteny or only microsyntenic regions encompassing usually five or fewer genes. To test the hypothesis that chromosomal evolution is different in the fungi compared to other eukaryotes, synteny was compared between species of the major fungal taxa. 相似文献10.