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Summary Uniformly14C labelled glucose, cellulose and wheat straw and specifically14C labelled lignin component in corn stalks were aerobically incubated for 12 weeks in a chernozem soil alongwith15N labelled ammonium sulphate. Glucose was most readily decomposed, followed in order by cellulose, wheat straw and corn stalk lignins labelled at methoxyl-, side chain 2-and ring-C. More than 50% of14C applied as glucose, cellulose and wheat straw evolved as CO2 during the first week. Lignin however, decomposed relatively slowly. A higher proportion of14C was transformed into microbial biomass whereas lignins contributed a little to this fraction.After 12 weeks of incubation nearly 60% of the lignin14C was found in humic compounds of which more than 70% was resistant to hydrolysis with 6N HCl. Maximum incorporation of15N in humic compounds was observed in cellulose amended soil. However, in this case more than 80% of the15N was in hydrolysable forms.Immobilization-remineralization of applied15N was most rapid in glucose treated soil and a complete immobilization followed by remineralization was observed after 3 days. The process was much slow in soil treated with cellulose, wheat straw or corn stalks. More than 70% of the newly immobilized N was in hydrolysable forms mainly reepresenting the microbial component.Serial hydrolysis of soil at different incubation intervals showed a greater proportion of 6N HCl hydrolysable14C and15N in fractions representing microbial material.14C from lignin carbons was relatively more uniformly distributed in different fractions as compared to glucose, cellulose and wheat straw where a major portion of14C was in easily hydrolysable fractions. 相似文献
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Luke R. Joyce Haider S. Manzer Jssica da C. Mendona Ricardo Villarreal Prescilla E. Nagao Kelly S. Doran Kelli L. Palmer Ziqiang Guan 《PLoS biology》2022,20(2)
Bacterial membrane lipids are critical for membrane bilayer formation, cell division, protein localization, stress responses, and pathogenesis. Despite their critical roles, membrane lipids have not been fully elucidated for many pathogens. Here, we report the discovery of a novel cationic glycolipid, lysyl-glucosyl-diacylglycerol (Lys-Glc-DAG), which is synthesized in high abundance by the bacterium Streptococcus agalactiae (Group B Streptococcus, GBS). To our knowledge, Lys-Glc-DAG is more positively charged than any other known lipids. Lys-Glc-DAG carries 2 positive net charges per molecule, distinct from the widely described lysylated phospholipid lysyl-phosphatidylglycerol (Lys-PG) that carries one positive net charge due to the presence of a negatively charged phosphate moiety. We use normal phase liquid chromatography (NPLC) coupled with electrospray ionization (ESI) high-resolution tandem mass spectrometry (HRMS/MS) and genetic approaches to determine that Lys-Glc-DAG is synthesized by the enzyme MprF in GBS, which covalently modifies the neutral glycolipid Glc-DAG with the cationic amino acid lysine. GBS is a leading cause of neonatal meningitis, which requires traversal of the endothelial blood–brain barrier (BBB). We demonstrate that GBS strains lacking mprF exhibit a significant decrease in the ability to invade BBB endothelial cells. Further, mice challenged with a GBSΔmprF mutant developed bacteremia comparably to wild-type (WT) infected mice yet had less recovered bacteria from brain tissue and a lower incidence of meningitis. Thus, our data suggest that Lys-Glc-DAG may contribute to bacterial uptake into host cells and disease progression. Importantly, our discovery provides a platform for further study of cationic lipids at the host–pathogen interface.Bacterial membrane lipids are critical for membrane bilayer formation, cell division, protein localization, stress responses, and pathogenesis. This study shows that the enzyme MprF in Streptococcus agalactiae synthesizes a novel cationic lipid, Lysyl-Glucosyl-Diacylglycerol, which aids meningitis progression in vivo. 相似文献
905.
T G Urmancheeva Kh Baumann V A Khasabova G Martin I F Vol'ter 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1977,27(1):64-72
It has been shown in experiments on three rhesus monkeys that an enhanced stress of analytical-synthetic processes consisting in learning to differentiate a sequence of tones, leads to neurotic disorders of monkeys higher nervous activity. They are manifested individually and consist in disturbances of general behaviour, in forced movements, breakdowns of differentiations, the missing of positive responses in the previously elaborated conditioned stereotype and in typical dynamics of the formation of positive and negative conditioned reflexes to a chain of tones (2000 + + 4000 c/s; 2000 + 2000 c/s; 4000 + 2000 c/s; 4000 + 4000 c/s). 相似文献
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The paper is concerned with retrospective analysis of CT scans of 507 patients without signs of diaphragmatic pathology to investigate normal roentgeno-anatomy of the diaphragm in CT imaging. The four main variants (types) in the structure of the lumbar diaphragm were singled out. CT was shown effective in the determination of pathological changes of the lumbar diaphragm and adjacent zones. It is an informative method among diagnostic procedures used in diaphragmatic diseases. 相似文献
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