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排序方式: 共有104条查询结果,搜索用时 15 毫秒
91.
Abstract: Electron microscopic and biochemical studies of lignocellulose degradation by wood-rotting fungi have shown that enzymes such as lignin peroxidases, manganese-dependent peroxidases, laccases and cellulases are too large to penetrate undegraded secondary wood cell walls. Degradation occurs by surface interaction between cell wall and enzymes, but initiation of decay at a distance from the fungal hyphae must involve diffusible low-molecular mass agents. The roles of hydrogen peroxide, veratryl alcohol, oxalate, Fe2+ -Fe3+ and Mn2+ -Mn3+ , as such agents in lignocellulose degradation are discussed. 相似文献
92.
Oxalic acid is produced by some species of plants and mycorrhizal fungi and it may solubilize unavailable soil phosphorus (P) bound by cations (Ca++, Al++, Fe+++). Field and greenhouse experiments were conducted to show whether oxalate produced by the annual Salsola tragus or added oxalic acid would solubilize P from the inorganic-bound soil P pool, making it available for uptake by Stipa pulchra. Oxalate could be leached in the laboratory from the senescent canopy of Salsola, and leaching by rainfall was hypothesized to be a source of potential increased soil P under the Salsola canopy. Both oxalate leached from the canopy of Salsola and added oxalic acid increased the availability of soil P in greenhouse experiments. The source of the increase in available soil P in the greenhouse experiment was shown to be the inorganic-bound P pool, as the total P concentration of the soil decreased with increasing oxalate. There were significant increases in Stipa shoot P in response to Salsola leachates and in response to added oxalate in the greenhouse studies. These results suggest an important role for oxalate in P cycling. On disturbed sites where Salsola invades it may act to facilitate the establishment of later seral species like Stipa by creating a nutrient island of available P. 相似文献
93.
Donald W. Bannister Iris E. ONeill 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1983,763(2):180-182
Addition of varying concentrations of oxalate to isolated chicken hepatocytes reduced gluconeogenesis from lactate in a manner indicating that pyruvate carboxylase was not the rate-limiting step. With hepatocytes from biotin-deficient chicks, sensitivity to inhibition was increased, and was consistent with pyruvate carboxylase being rate-limiting. Administration of biotin to deficient chicks overnight restores sensitivity to oxalate to normal. 相似文献
94.
Oxalobacter formigenes gen. nov., sp. nov.: oxalate-degrading anaerobes that inhabit the gastrointestinal tract 总被引:3,自引:0,他引:3
Milton J. Allison Karl A. Dawson William R. Mayberry John G. Foss 《Archives of microbiology》1985,141(1):1-7
This report describes a new group of anaerobic bacteria that degrade oxalic acid. The new genus and species, Oxalobacter formigenes, are inhabitants of the rumen and also of the large bowel of man and other animals where their actions in destruction of oxalic acid may be of considerable importance to the host. Isolates from the rumen of a sheep, the cecum of a pig, and from human feces were all similar Gram-negative, obligately anaerobic rods, but differences between isolates in cellular fatty acid composition and in serologic reaction were noted. Measurements made with type strain OxB indicated that 1 mol of protons was consumed per mol of oxalate degraded to produce approximately 1 mol of CO2 and 0.9 mol of formate. Substances that replaced oxalate as a growth substrate were not found. 相似文献
95.
Decarboxylation of dicarboxylic acids (oxalate, malonate, succinate, glutarate, and malate) can serve as the sole energy
source for the growth of fermenting bacteria. Since the free energy change of a decarboxylation reaction is small (around
–20 kJ per mol) and equivalent to only approximately one-third of the energy required for ATP synthesis from ADP and phosphate
under physiological conditions, the decarboxylation energy cannot be conserved by substrate-level phosphorylation. It is either
converted (in malonate, succinate, and glutarate fermentation) by membrane-bound primary decarboxylase sodium ion pumps into
an electrochemical gradient of sodium ions across the membrane; or, alternatively, an electrochemical proton gradient can
be established by the combined action of a soluble decarboxylase with a dicarboxylate/monocarboxylate antiporter (in oxalate
and malate fermentation). The thus generated electrochemical Na+ or H+ gradients are then exploited for ATP synthesis by Na+- or H+-coupled F1F0 ATP synthases. This new type of energy conservation has been termed decarboxylation phosphorylation and is responsible entirely
for ATP synthesis in several anaerobic bacteria.
Received: 5 December 1997 / Accepted: 16 March 1998 相似文献
96.
Katarína Valentovi
ov
ubica Halukov Jana Huttov Igor Mistrík Ladislav Tams 《Environmental and Experimental Botany》2009,66(3):457-462
The effect of Cd on oxalate oxidase (OxO) activity and its localisation were analysed in barley root. In Cd-treated roots OxO activity was strongly induced in the region 2–4 mm behind the root tip and in the area toward the root base. In situ analyses showed that Cd-induced OxO activity was localised to the cell wall (CW) of early metaxylem vascular bundles and surrounding parenchyma cells and was accompanied by lignification of metaxylem vessels. OxO activation was also observed during treatment with other heavy metals (HMs), salt treatment and at elevated non-optimal temperature. In contrast to HM activation of OxO and lignification, high temperature and NaCl indeed activated OxO but did not induce lignification of metaxylem vessels. These results suggest that oxalate oxidase as an H2O2-generating enzyme is activated in response to several stresses, however the ectopic lignification of metaxylem vessels is activated specifically by HMs. This HM-induced premature root xylogenesis due to ectopic lignification of metaxylem vessels probably causes shortening of the root elongation zone and therefore a reduction in root growth. 相似文献
97.
《Fungal Biology Reviews》2014,28(2-3):36-55
Oxalate is a key metabolite that plays a significant role in many metal and mineral transformations mediated by fungi. Metal and mineral transformations are central to geomycological processes including nutrient and element cycling, rock, mineral and metal transformations, bioweathering and mycogenic biomineral formation. Some fungal transformations have potential applications in environmental biotechnology, e.g. metal and radionuclide leaching, biorecovery, detoxification and bioremediation, and in the production or deposition of biominerals or metallic elements with catalytic or other properties. Metal and mineral transformations may also result in adverse effects when these processes result in biodeterioration of natural and synthetic materials, rock and mineral-based building materials (e.g. concrete), biocorrosion of metals, alloys and related substances, and adverse effects on radionuclide speciation, mobility and containment. Oxalate is ubiquitous in all these contexts. This paper seeks to draw together salient information from environmental and applied research to emphasize the importance of oxalate in geomycology, biodeterioration, environmental biotechnology and bioremediation. 相似文献
98.
《Systematic and applied microbiology》2022,45(6):126373
The type strains of all 33 species in the genus Kribbella were tested for growth on oxalate (?OOC-COO?) as sole carbon source. Media were initially formulated to contain sodium oxalate, but even a concentration as low as 7.5 mM oxalate prevented growth. A modified medium based on calcium oxalate was very successful in characterising oxalate utilisation by Kribbella strains (metabolism of oxalate by oxalotrophic bacteria results in visible zones of clearing around the growth streaks on the opaque plates). To assess the variability of oxalate utilisation in Kribbella species, we also tested eight non-type strains for their ability to use oxalate. Thirty of 33 type strains (90.9%) and six of eight non-type strains (75%) were able to use oxalate as a sole carbon source. Based on these results, we propose that oxalate would be an excellent carbon source for the selective isolation of Kribbella strains. Based on the oxalate-utilisation phenotype and analyses of the 19 publicly available Kribbella type-strain genome sequences, we propose a pathway for oxalate metabolism in Kribbella. This pathway is significantly different from those previously proposed for oxalate metabolism in other bacteria, involving the indirect catabolism of oxalate to formate. Formate production is proposed to be involved in energy generation and to be crucial for oxalate import via an oxalate:formate antiporter. To our knowledge, this is the first report of an oxalate:formate antiporter in an aerobic, Gram-positive bacterium. 相似文献
99.
Although oxalic acid is common in nature our understanding of the mechanism(s) regulating its turnover remains incomplete. In this study we identify Saccharomyces cerevisiae acyl-activating enzyme 3 (ScAAE3) as an enzyme capable of catalyzing the conversion of oxalate to oxalyl-CoA. Based on our findings we propose that ScAAE3 catalyzes the first step in a novel pathway of oxalate degradation to protect the cell against the harmful effects of oxalate derived from an endogenous process or an environmental source. 相似文献
100.
Carbon-14 was incorporated from citrate-1,5-14C, glyoxylate-14C(U), or glyoxylate-1-14C into oxalate by cultures of Aspergillus niger pregrown on a medium with glucose as the sole source of carbon. Glyoxylate-14C(U) was superior to glyoxylate-1-14C and citrate-1,5-14C as a source of incorporation. By addition of a great amount of citrate the accumulation of oxalate was accelerated and its maximum yield increased. In a cell-free extract from mycelium forming oxalate from citrate the enzyme oxaloacetate hydrolase (EC 3.7.1.1) was identified. Its in vitro activity per flask exceeded the rate of in vivo accumulation of oxalate. Glyoxylate oxidizing enzymes (glycolate oxidase, EC 1.1.3.1; glyoxylate oxidase, EC 1.2.3.5; NAD(P)-dependent glyoxylate dehydrogenase; glyoxylate dehydrogenase, CoA-oxalylating, EC 1.2.1.17) could not be detected in cell-free extracts. It is concluded that in cultures accumulating oxalate from citrate after pregrowth on glucose, oxalate arises by hydrolytic cleavage of oxaloacetate but not by oxidation of glyoxylate.Abbreviations Used DCPIP
2,6-dichlorophenolindophenol 相似文献