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101.
102.
Axel FeyRalf Conrad 《Soil biology & biochemistry》2003,35(1):1-8
Temperature is an important factor controlling CH4 production in rice field soils. However, it is unknown which step in the methanogenic degradation of organic matter is the limiting one that is controlled by temperature. Soil slurries prepared from Italian rice field soil were anaerobically incubated in the dark at six different temperatures between 10 and 37 °C until quasi-steady state was reached. Then, the potential and actual rates of polysaccharide hydrolysis and of CH4 production from different immediate (acetate, H2) and distal (glucose, propionate) methanogenic substrates were determined. Potential activities of exo-glucanase and glucosidase were always higher than the actual rates of polysaccharide hydrolysis indicating that the availability of the polysaccharide substrate was limiting at all temperatures. The actual rates of CH4 production were always lower than those predicted from glucose release during polysaccharide hydrolysis indicating that a substantial amount of the released glucose was assimilated into microbial biomass. Addition of the different methanogenic substrates stimulated CH4 production at all temperatures >10 °C, but only at >20 °C to values higher than rates of polysaccharide hydrolysis. Under steady state conditions, however, hydrolysis of organic polymers was the rate-limiting step at all temperatures >10 °C. 相似文献
103.
A close correlation exists between dissolved organic carbon (DOC) concentration and UV absorbance at 254 nm (A254) in natural waters. DOC and A254 were measured for soil solutions, throughfall, stemflow, and surface waters collected from a forested site located in eastern Austria. The slopes of lines determined by linear regression of DOC versus UV absorbance were very similar to those determined for wet deposition and throughfall samples collected in Nordrhein-Westfalen, Germany by Bartels (1988). The intercept of the regression line in the current study indicates that approximately 1 mg L1 of non-UV-absorbing DOC is present; it is suggested that this is due to saturated aliphatic compounds such as acetate or formate. 相似文献
104.
Thomas Bartels Dr. Rer. Nat. Jürgen Brinkmeier Dr. Med. Vet. Susanne Portmann Med. Vet. Ulrich Baulain Dr. sc. Agr. Axel Zinke Dr. Med. Vet. Maria-Elisabeth Krautwald-Junghanns Prof. Dr. Med. Vet. Alois Boos PD Dr. Med. Vet. Petra Wolf Dr. Med. Vet. Norbert Kummerfeld Dr. Med. Vet 《Veterinary radiology & ultrasound》2001,42(3):254-258
The crested breed of domestic duck (Anas platyrhynchos f. dom.) has been described as a variety which has high pre- and postnatal mortalities, malformations in skull and brain anatomy, and several central nervous deficiencies. In addition, intracranial tissue accumulations have been diagnosed in purebred Crested ducks. The incidence, heredity and inheritance of these accumulations as well as their pathogenesis are still generally unknown. The aims of this study were to examine the head of Crested ducks, plain-headed duck breeds, and their crossbreeding relating to the incidence of intracranial alterations. These examinations were performed using magnetic resonance imaging. We found a high incidence of intracranial tissue accumulations in domestic ducks with feather crests. Creasted ducks had more intracranial tissue deposits than plain-headed ducks (p < 0.001). In the present study a correlation between the volume of the crest cushion and the volume of the intracranial tissue deposit could not be found (r = 0.014). Some of the Crested ducks had encephaloceles in addition to the crest cushion. 相似文献
105.
Esposito LW Colwell JE Larsen K McClintock WE Stewart AI Hallett JT Shemansky DE Ajello JM Hansen CJ Hendrix AR West RA Keller HU Korth A Pryor WR Reulke R Yung YL 《Science (New York, N.Y.)》2005,307(5713):1251-1255
Neutral oxygen in the saturnian system shows variability, and the total number of oxygen atoms peaks at 4 x 10(34). Saturn's aurora brightens in response to solar-wind forcing, and the auroral spectrum resembles Jupiter's. Phoebe's surface shows variable water-ice content, and the data indicate it originated in the outer solar system. Saturn's rings also show variable water abundance, with the purest ice in the outermost A ring. This radial variation is consistent with initially pure water ice bombarded by meteors, but smaller radial structures may indicate collisional transport and recent renewal events in the past 10(7) to 10(8) years. 相似文献
106.
Marchal A Marullo P Moine V Dubourdieu D 《Journal of agricultural and food chemistry》2011,59(5):2004-2010
Yeast autolysis during lees contact influences the organoleptic properties of wines especially by increasing their sweet taste. Although observed by winemakers, this phenomenon is poorly explained in enology. Moreover, the compounds responsible for sweetness in wine remain unidentified. This work provides new insights in this way by combining sensorial, biochemical and genetic approaches. First, we verified by sensory analysis that yeast autolysis in red wine has a significant effect on sweetness. Moderate additions of ethanol or glycerol did not have the same effect. Second, a sapid fraction was isolated from lees extracts by successive ultrafiltrations and HPLC purifications. Using nano-LC-MS/MS, peptides released by the yeast heat shock protein Hsp12p were distinctly identified in this sample. Third, we confirmed the sweet contribution of this protein by sensorial comparison of red wines incubated with two kinds of yeast strains: a wild-type strain containing the native Hsp12p and a deletion mutant strain that lacks the Hsp12p protein (Δ°HSP12 strain). Red wines incubated with wild-type strain showed a significantly higher sweetness than control wines incubated with Δ°HSP12 strains. These results demonstrated the contribution of protein Hsp12p in the sweet perception consecutive to yeast autolysis in wine. 相似文献
107.
108.
Brüggemann H Henne A Hoster F Liesegang H Wiezer A Strittmatter A Hujer S Dürre P Gottschalk G 《Science (New York, N.Y.)》2004,305(5684):671-673
Propionibacterium acnes is a major inhabitant of adult human skin, where it resides within sebaceous follicles, usually as a harmless commensal although it has been implicated in acne vulgaris formation. The entire genome sequence of this Gram-positive bacterium encodes 2333 putative genes and revealed numerous gene products involved in degrading host molecules, including sialidases, neuraminidases, endoglycoceramidases, lipases, and pore-forming factors. Surface-associated and other immunogenic factors have been identified, which might be involved in triggering acne inflammation and other P. acnes-associated diseases. 相似文献
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110.