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11.
Amino acid and lactate catabolism in trimethylamine oxide respiration of Alteromonas putrefaciens NCMB 1735 总被引:1,自引:0,他引:1
The nonfermentative Alteromonas putrefaciens NCMB 1735 grew anaerobically in defined media with trimethylamine oxide as external electron acceptor. All amino acids tested, except taurine and those with a cyclic or aromatic side chain, were utilized during trimethylamine oxide-dependent anaerobic growth. Lactate, serine, and cysteine (which are easily converted to pyruvate) and glutamate and aspartate (which are easily converted to tricarboxylic acid cycle intermediates) were metabolized at the fastest rate. Growth with lactate as growth-limiting substrate gave rise to the formation of 40 mol% acetate, whereas serine and cysteine were nearly completely oxidized to CO2. Molar growth yields with the latter substrates were the same and were 50% higher than with lactate. This showed that more ATP was formed when acetyl coenzyme A entered the tricarboxylic acid cycle than when it was converted via acetyl phosphate to acetate. Also, growth with formate as substrate indicated that the reduction of trimethylamine oxide to trimethylamine was coupled with energy conservation by a respiratory mechanism. 相似文献
12.
Amino acid and lactate catabolism in trimethylamine oxide respiration of Alteromonas putrefaciens NCMB 1735. 总被引:3,自引:2,他引:1
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The nonfermentative Alteromonas putrefaciens NCMB 1735 grew anaerobically in defined media with trimethylamine oxide as external electron acceptor. All amino acids tested, except taurine and those with a cyclic or aromatic side chain, were utilized during trimethylamine oxide-dependent anaerobic growth. Lactate, serine, and cysteine (which are easily converted to pyruvate) and glutamate and aspartate (which are easily converted to tricarboxylic acid cycle intermediates) were metabolized at the fastest rate. Growth with lactate as growth-limiting substrate gave rise to the formation of 40 mol% acetate, whereas serine and cysteine were nearly completely oxidized to CO2. Molar growth yields with the latter substrates were the same and were 50% higher than with lactate. This showed that more ATP was formed when acetyl coenzyme A entered the tricarboxylic acid cycle than when it was converted via acetyl phosphate to acetate. Also, growth with formate as substrate indicated that the reduction of trimethylamine oxide to trimethylamine was coupled with energy conservation by a respiratory mechanism. 相似文献
13.
Hydroxylation of androstenedione was studied in rat hepatocytes in primary monolayer culture following induction with phenobarbital. Six days after addition of phenobarbital and seven days after isolation of cells from liver, a maximal induction of total androstenedione hydroxylation of 5–6 times was seen at a phenobarbital concentration of 1·10−4 M. The 6β-, 7α- and 16α-hydroxylase activities showed different responses towards phenobarbital in agreement with the contension that different forms of cytochrome P-450 with different sensitivity towards phenobarbital participate in hepatic steroid hydroxylation. These results were obtained with cells supplemented with 1% (v/v) rat serum. The present cell culture system should be suitable for in vitro studies on mechanisms of induction of cytochrome P-450-dependent enzymes in normal liver cells. 相似文献
14.
A rapid, sensitive, and specific procedure has been developed for detection of transsamidatingenzymes (transglutaminase, e.g., factor XIII) after agarose gel electrophoresis. The technique is based on the transamidase-catalyzed incorporation of the fluorescent monodansylthiacadaverine into casein. The high sensitivity enables detection and characterization of transamidases in blood plasma, platelet, and red blood cell lysate and tissue extracts. The technique can also be combined with crossed immunoelectrophoresis. 相似文献
15.
The electrostatic interaction between charges within a nerve membrane is considered. It is seen that the electrostatic repulsion between so called gating particles of an ionic channel cannot be neglected in the formulation of excitability models based on gating charges. Some general conclusions are drawn about different models for nerve membrane excitability. 相似文献
16.
Computer simulation of surface-induced aggregation of ferritin. 总被引:2,自引:0,他引:2
Models are presented describing the transient mass-transport limited adsorption and cluster growth of ferritin at a solid surface. Computer simulations are carried out on a hexagonal lattice using a computer model that can be characterized as a two-dimensional stochastic cellular automaton allowing different rules regarding association, lateral interaction and dissociation to be incorporated in the model. The fractal dimensions of individual clusters were extracted from simulated aggregates and for similar rules found to be consistent with literature values on reversible diffusion-limited aggregation in two dimensions. The distribution of clusters versus free surface were shown to be affected by neighbor-dependent association probability. Low fractal dimension clusters were generated by a combination of strong lateral cohesion and neighbor-dependent dissociation to the bulk. By comparing computer simulated aggregation to experimental electron micrographs of adsorbed ferritin layers it is suggested that neighbor-dependent association, neighbor-dependent dissociation and lateral interactions are important factors in the complex dynamics of adsorbed protein layers. 相似文献
17.
Marika A. Schulhof Andrew E. Allen Eric E. Allen Natalie Mladenov John P. McCrow Natalie T. Jones Jessica Blanton Hamanda B. Cavalheri Drishti Kaul Celia C. Symons Jonathan B. Shurin 《Molecular ecology》2020,29(11):2080-2093
Warming, eutrophication (nutrient fertilization) and brownification (increased loading of allochthonous organic matter) are three global trends impacting lake ecosystems. However, the independent and synergistic effects of resource addition and warming on autotrophic and heterotrophic microorganisms are largely unknown. In this study, we investigate the independent and interactive effects of temperature, dissolved organic carbon (DOC, both allochthonous and autochthonous) and nitrogen (N) supply, in addition to the effect of spatial variables, on the composition, richness, and evenness of prokaryotic and eukaryotic microbial communities in lakes across elevation and N deposition gradients in the Sierra Nevada mountains of California, USA. We found that both prokaryotic and eukaryotic communities are structured by temperature, terrestrial (allochthonous) DOC and latitude. Prokaryotic communities are also influenced by total and aquatic (autochthonous) DOC, while eukaryotic communities are also structured by nitrate. Additionally, increasing N availability was associated with reduced richness of prokaryotic communities, and both lower richness and evenness of eukaryotes. We did not detect any synergistic or antagonistic effects as there were no interactions among temperature and resource variables. Together, our results suggest that (a) organic and inorganic resources, temperature, and geographic location (based on latitude and longitude) independently influence lake microbial communities; and (b) increasing N supply due to atmospheric N deposition may reduce richness of both prokaryotic and eukaryotic microbes, probably by reducing niche dimensionality. Our study provides insight into abiotic processes structuring microbial communities across environmental gradients and their potential roles in material and energy fluxes within and between ecosystems. 相似文献
18.
Marika Crohns Seppo Saarelainen Jukka Laitinen Kimmo Peltonen Hannu Alho Pirkko Kellokumpu-Lehtinen 《Free radical research》2013,47(10):965-974
To examine lipid peroxidation during radiotherapy (RT), exhaled pentane samples were collected from 11 lung cancer patients before RT and 30 and 120 min after the start of RT on days 1, 4 and 5 and at 30 and 40 Grays, if possible. Exhaled pentane samples were collected once from 30 healthy controls. Serum thiobarbituric-acid-reactive substances (TBARS) and conjugated dienes (CD) were obtained from patients on each exhaled air collection day. Lung cancer patients had higher exhaled pentane levels than controls (1.73 ng/L vs 0.83 ng/L, p=0.017). Exhaled pentane levels tended to decrease during the first RT day (p=0.075) and levels of CD decreased during the first week of RT (p=0.014). Higher pre-treatment pentane levels predicted better survival (p=0.003). Elevated exhaled pentane levels before RT may be due to the lipid peroxidation burden associated with cancer. The decrease of lipid peroxidation markers during RT may be attributable to enhanced antioxidant defense mechanisms. 相似文献
19.
20.
Jérémy Jabiol Andreas Bruder Mark O. Gessner Marika Makkonen Brendan G. McKie Edwin T.H.M. Peeters Veronique C.A. Vos Eric Chauvet 《Fungal Ecology》2013,6(5):439-448
Information about the global distribution of aquatic hyphomycetes is scarce, despite the primary importance of these fungi in stream ecosystem functioning. In particular, the relationship between their diversity and latitude remains unclear, due to a lack of coordinated surveys across broad latitudinal ranges. This study is a first report on latitudinal patterns of aquatic hyphomycete diversity associated with native leaf-litter species in five streams located along a gradient extending from the subarctic to the tropics. Exposure of leaf litter in mesh bags of three different mesh sizes facilitated assessing the effects of including or excluding different size-classes of litter-consuming invertebrates. Aquatic hyphomycete evenness was notably constant across all sites, whereas species richness and diversity, expressed as the Hill number, reached a maximum at mid-latitudes (Mediterranean and temperate streams). These latitudinal patterns were consistent across litter species, despite a notable influence of litter identity on fungal communities at the local scale. As a result, the bell-shaped distribution of species richness and Hill diversity deviated markedly from the latitudinal patterns of most other groups of organisms. Differences in the body-size distribution of invertebrate communities colonizing the leaves had no effect on aquatic hyphomycete species richness, Hill diversity or evenness, but invertebrates could still influence fungal communities by depleting litter, an effect that was not captured by the design of our experiment. 相似文献