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排序方式: 共有270条查询结果,搜索用时 703 毫秒
21.
Composting is characterized by dramatic changes in microbial community structure, to a high extent driven by changes in temperature
and in the composition of the organic substrate. This study focuses on the interrelationships between decomposition of major
classes in the organic material and dynamics in microbial populations during thermophilic composting of source-separated organic
household waste.
Experiments were performed in a 200-L laboratory reactor at 16, 2.5, and 1% O2 in the compost atmosphere. Major classes of carbon constituents were analyzed by chemical methods, and the microbial biomass
and community structure determined by fatty acid analyses with phospholipid fatty acids (PLFA) and total ester-linked fatty
acids (EL) methods. At all three O2 levels, the process was characterized by a rapid increase in microbial activity and biomass in the early thermophilic phase,
although this period was delayed at the lower O2 concentrations. Starch and fat were the main substrates utilized at all three O2 levels during this period. The depletion of the starch fraction coincided with the beginning of a microbial biomass decrease,
suggesting thatstarch is an important carbon substrate for the growth of thermophilic microorganisms during composting. Growth
yields in the microbial community based on consumption of major carbon constituent classes in the high-activity period fell
between 22 and 28%. Multivariate statistical analysis of changes in fatty acid composition revealed small, but statistically
significant differences in the microbial community succession. At 16% O2, 10Me fatty acids from Actinomycetes and cyclopropyl fatty acids (from Gram-negative bacteria) became more important with
time, whereas 18:1ω7t was characteristic at 2.5 and 1% O2, indicating a more stressed bacterial community at the lower O2 concentrations.
Although adequate composting was achieved at O2 levels as low as 2.5 and 1%, it is not recommended to compost at such low levels in large-scale systems, because the heterogeneous
gas transport through the material in these systems might lead to anaerobic conditions and inefficient composting. 相似文献
22.
Svedruzić D Jónsson S Toyota CG Reinhardt LA Ricagno S Lindqvist Y Richards NG 《Archives of biochemistry and biophysics》2005,433(1):176-192
Oxalate degrading enzymes have a number of potential applications, including medical diagnosis and treatments for hyperoxaluria and other oxalate-related diseases, the production of transgenic plants for human consumption, and bioremediation of the environment. This review seeks to provide a brief overview of current knowledge regarding the major classes of enzymes and related proteins that are employed in plants, fungi, and bacteria to convert oxalate into CO(2) and/or formate. Not only do these enzymes employ intriguing chemical strategies for cleaving the chemically unreactive C-C bond in oxalate, but they also offer the prospect of providing new insights into the molecular processes that underpin the evolution of biological catalysts. 相似文献
23.
Ylva Hedberg Anne-Marie Dalin Malin Santesson Hans Kindahl 《Acta veterinaria Scandinavica》2006,48(1):12-6
Background
Strong oestrous symptoms in the mare can cause problems with racing, training and handling. Since long-acting progesterone treatment is not permitted in mares at competition (e.g. according to FEI rules), there is a need for methods to suppress unwanted cyclicity. Spontaneous dioestrous ovulations in the late luteal phase may cause a prolongation of the luteal phase in mares. 相似文献24.
Tina Boddum Niels Skals Bill S. Hansson Ylva Hillbur 《Journal of insect physiology》2010,56(9):1306-711
This study describes the morphology and function of the antennal sensilla in two gall midge species, Contarinia nasturtii and Mayetiola destructor, where multi-component sex pheromones have been identified. Both species possess sensilla trichodea, s. coeloconica, s. chaetica and s. circumfila. Sensilla circumfila, which consist of several sensilla that bifurcate and fuse into one structure, are unique for the gall midges. In C. nasturtii s. circumfila are sexually dimorphic. In males, they form elongated loops suspended on cuticular spines, whereas in females they run like worm-like structures directly on the antennal surface. Single sensillum recordings demonstrated that olfactory sensory neurons housed in male s. circumfila in C. nasturtii responded to the female sex pheromone. In M. destructor, s. circumfila were attached to the antennal surface in both sexes, and displayed no response to sex pheromone components.A sexual dimorphism was also found in the number of s. trichodea per antennal segment in both C. nasturtii (male 1 vs. female 7) and M. destructor (male 13 vs. female 10). OSNs located in male M. destructor s. trichodea responded to the sex pheromone. This is the first gall midge single sensillum study, and the first demonstration of the functional significance of s. circumfila. 相似文献
25.
Flavour formation by amino acid catabolism 总被引:18,自引:0,他引:18
Ardö Y 《Biotechnology advances》2006,24(2):238-242
Microbial catabolism of amino acids produces flavour compounds of importance for foods such as cheese, wine and fermented sausages. Lactic acid bacteria are equipped with enzyme systems for using the amino acids in their metabolism and are useful for flavour formation of foods. Branched-chain amino acids (Leu, Ile, Val) are converted into compounds contributing to malty, fruity and sweaty flavours; catabolism of aromatic amino acids (Phe, Tyr, Trp) produce floral, chemical and faecal flavours; aspartic acid (Asp) is catabolised into buttery flavours and sulphuric amino acids (Met, Cys) are transferred into compounds contributing to boiled cabbage, meaty and garlic flavours. 相似文献
26.
27.
Hernández J Stedt J Bonnedahl J Molin Y Drobni M Calisto-Ulloa N Gomez-Fuentes C Astorga-España MS González-Acuña D Waldenström J Blomqvist M Olsen B 《Applied and environmental microbiology》2012,78(6):2056-2058
Escherichia coli bacteria with extended-spectrum β-lactamase (ESBL) type CTX-M resistance were isolated from water samples collected close to research stations in Antarctica. The isolates had bla(CTX-M-1) and bla(CTX-M-15) genotypes and sequence types (ST) indicative of a human-associated origin. This is the first record of ESBL-producing enterobacteria from Antarctica. 相似文献
28.
29.
Skeletal muscle lipid accumulation is associated with several chronic metabolic disorders, including obesity, insulin resistance (IR) and type 2 diabetes. The aim of this study is to evaluate whether static imaging time-of-flight-secondary-ion mass spectrometry (TOF-SIMS) equipped with a Bismuth-cluster ion source can be used for studying skeletal muscle lipid accumulation associated with obesity. Mouse gastrocnemius muscle tissues in 10-week-old obese ob/ob (n = 8) and lean wild-type C57/BL6 (n = 6) mice were analyzed by TOF-SIMS. Our results showed that signal intensities of fatty acids (FAs) and diacylglycerols (DAGs) were significantly increased in skeletal muscle of the obese ob/ob mice as compared to the lean wild-type mice. These differences were revealed through a global analytical approach, principal component analysis (PCA) of TOF-SIMS spectra, and ion-specific TOF-SIMS images. Region-of-interest (ROI) analysis showed that FA signal intensities within the muscle cell were significantly increased in ob/ob mice. Moreover, analysis of the ratio between different FA peaks revealed changes in monounsaturated FAs (MUFAs) and polyunsaturated FAs (PUFAs), which is in agreement with previous reports on obesity. These changes in FA composition were also reflected in the ratio of different DAGs or phosphatidylcholines (PCs) that contain different FA residues. Imaging TOF-SIMS together with PCA of TOF-SIMS spectra is a promising tool for studying skeletal muscle lipid accumulation associated with obesity. 相似文献
30.