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Cloning of the Malic Enzyme Gene from Corynebacterium glutamicum and Role of the Enzyme in Lactate Metabolism 下载免费PDF全文
Pierre Gourdon Marie-France Baucher Nic D. Lindley Armel Guyonvarch 《Applied microbiology》2000,66(7):2981-2987
Malic enzyme is one of at least five enzymes, known to be present in Corynebacterium glutamicum, capable of carboxylation and decarboxylation reactions coupling glycolysis and the tricarboxylic acid cycle. To date, no information is available concerning the physiological role of the malic enzyme in this bacterium. The malE gene from C. glutamicum has been cloned and sequenced. The protein encoded by this gene has been purified to homogeneity, and the biochemical properties have been established. Biochemical characteristics indicate a decarboxylation role linked to NADPH generation. Strains of C. glutamicum in which the malE gene had been disrupted or overexpressed showed no detectable phenotype during growth on either acetate or glucose, but showed a significant modification of growth behavior during lactate metabolism. The wild type showed a characteristic brief period of exponential growth on lactate followed by a linear growth period. This growth pattern was further accentuated in a malE-disrupted strain (ΔmalE). However, the strain overexpressing malE maintained exponential growth until all lactate had been consumed. This strain accumulated significantly larger amounts of pyruvate in the medium than the other strains. 相似文献
104.
Annelene Pengerud Marie-France Dignac Giacomo Certini Line Tau Strand Claudia Forte Daniel P. Rasse 《Biogeochemistry》2017,135(3):277-292
Increased mineralization of the organic matter (OM) stored in permafrost is expected to constitute the largest additional global warming potential from terrestrial ecosystems exposed to a warmer climate. Chemical composition of permafrost OM is thought to be a key factor controlling the sensitivity of decomposition to warming. Our objective was to characterise OM from permafrost soils of the European Arctic: two mineral soils—Adventdalen, Svalbard, Norway and Vorkuta, northwest Russia—and a “palsa” (ice-cored peat mound patterning in heterogeneous permafrost landscapes) soil in Neiden, northern Norway, in terms of molecular composition and state of decomposition. At all sites, the OM stored in the permafrost was at an advanced stage of decomposition, although somewhat less so in the palsa peat. By comparing permafrost and active layers, we found no consistent effect of depth or permafrost on soil organic matter (SOM) chemistry across sites. The permafrost-affected palsa peat displayed better preservation of plant material in the deeper layer, as indicated by increasing contribution of lignin carbon to total carbon with depth, associated to decreasing acid (Ac) to aldehyde (Al) ratio of the syringyl (S) and vanillyl (V) units, and increasing S/V and contribution of plant-derived sugars. By contrast, in Adventdalen, the Ac/Al ratio of lignin and the Alkyl C to O-alkyl C ratio in the NMR spectra increased with depth, which suggests less oxidized SOM in the active layer compared to the permafrost layer. In Vorkuta, SOM characteristics in the permafrost profile did not change substantially with depth, probably due to mixing of soil layers by cryoturbation. The composition and state of decomposition of SOM appeared to be site-specific, in particular bound to the prevailing organic or mineral nature of soil when attempting to predict the SOM proneness to degradation. The occurrence of processes such as palsa formation in organic soils and cryoturbation should be considered when up-scaling and predicting the responses of OM to climate change in arctic soils. 相似文献
105.
Soil microbial diversity affects soil organic matter decomposition in a silty grassland soil 总被引:1,自引:0,他引:1
Karen Baumann Marie-France Dignac Cornelia Rumpel Gérard Bardoux Amadou Sarr Markus Steffens Pierre-Alain Maron 《Biogeochemistry》2013,114(1-3):201-212
Soil microorganisms play a pivotal role in soil organic matter (SOM) turn-over and their diversity is discussed as a key to the function of soil ecosystems. However, the extent to which SOM dynamics may be linked to changes in soil microbial diversity remains largely unknown. We characterized SOM degradation along a microbial diversity gradient in a two month incubation experiment under controlled laboratory conditions. A microbial diversity gradient was created by diluting soil suspension of a silty grassland soil. Microcosms containing the same sterilized soil were re-inoculated with one of the created microbial diversities, and were amended with 13C labeled wheat in order to assess whether SOM decomposition is linked to soil microbial diversity or not. Structural composition of wheat was assessed by solid-state 13C nuclear magnetic resonance, sugar and lignin content was quantified and labeled wheat contribution was determined by 13C compound specific analyses. Results showed decreased wheat O-alkyl-C with increasing microbial diversity. Total non-cellulosic sugar-C derived from wheat was not significantly influenced by microbial diversity. Carbon from wheat sugars (arabinose-C and xylose-C), however, was highest when microbial diversity was low, indicating reduced wheat sugar decomposition at low microbial diversity. Xylose-C was significantly correlated with the Shannon diversity index of the bacterial community. Soil lignin-C decreased irrespective of microbial diversity. At low microbial diversity the oxidation state of vanillyl–lignin units was significantly reduced. We conclude that microbial diversity alters bulk chemical structure, the decomposition of plant litter sugars and influences the microbial oxidation of total vanillyl–lignins, thus changing SOM composition. 相似文献
106.
The use of bacteriophage depolymerization in the structural investigation of the capsular polysaccharide from Klebsiella serotype K3 总被引:1,自引:0,他引:1
The structure of the repeating unit of the capsular polysaccharide from Klebsiella serotype K3 has been established from the results of n.m.r. (1H and 13C) spectroscopy and methylation analysis of P1, the pyruvic acetal-bearing pentasaccharide obtained on depolymerization of the polysaccharide with a bacteriophage-borne endogalactosidase, reduced deacetalated P1, and the native polysaccharide. The data permit the assignment of the following structure to the repeating unit: (formula see text) 相似文献
107.
108.
M. Lebouvier M. Laparie M. Hullé A. Marais Y. Cozic L. Lalouette P. Vernon T. Candresse Y. Frenot David Renault 《Biological invasions》2011,13(5):1195-1208
The suite of environments and anthropogenic modifications of sub-Antarctic islands provide key opportunities to improve our
understanding of the potential consequences of climate change and biological species invasions on terrestrial ecosystems.
The profound impact of human introduced invasive species on indigenous biota, and the facilitation of establishment as a result
of changing thermal conditions, has been well documented on the French sub-Antarctic Kerguelen Islands (South Indian Ocean).
The present study provides an overview of the vulnerability of sub-Antarctic terrestrial communities with respect to two interacting
factors, namely climate change and alien insects. We present datasets assimilated by our teams on the Kerguelen Islands since
1974, coupled with a review of the literature, to evaluate the mechanism and impact of biological invasions in this region.
First, we consider recent climatic trends of the Antarctic region, and its potential influence on the establishment, distribution
and abundance of alien insects, using as examples one fly and one beetle species. Second, we consider to what extent limited
gene pools may restrict alien species’ colonisations. Finally, we consider the vulnerability of native communities to aliens
using the examples of one beetle, one fly, and five aphid species taking into consideration their additional impact as plant
virus vectors. We conclude that the evidence assimilated from the sub-Antarctic islands can be applied to more complex temperate
continental systems as well as further developing international guidelines to minimise the impact of alien species. 相似文献
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110.
Eric Batard Fréderic Jamme Sandrine Villette Cédric Jacqueline Marie-France de la Cochetière Jocelyne Caillon Matthieu Réfrégiers 《PloS one》2011,6(4)
The diffusion of antibiotics in endocarditis vegetation bacterial masses has not
been described, although it may influence the efficacy of antibiotic therapy in
endocarditis. The objective of this work was to assess the diffusion of
ofloxacin in experimental endocarditis vegetation bacterial masses using
synchrotron-radiation UV fluorescence microspectroscopy. Streptococcal
endocarditis was induced in 5 rabbits. Three animals received an unique IV
injection of 150 mg/kg ofloxacin, and 2 control rabbits were left untreated. Two
fluorescence microscopes were coupled to a synchrotron beam for excitation at
275 nm. A spectral microscope collected fluorescence spectra between 285 and 550
nm. A second, full field microscope was used with bandpass filters at
510–560 nm. Spectra of ofloxacin-treated vegetations presented higher
fluorescence between 390 and 540 nm than control. Full field imaging showed that
ofloxacin increased fluorescence between 510 and 560 nm. Ofloxacin diffused into
vegetation bacterial masses, although it accumulated in their immediate
neighborhood. Fluorescence images additionally suggested an ofloxacin
concentration gradient between the vegetation peripheral and central areas. In
conclusion, ofloxacin diffuses into vegetation bacterial masses, but it
accumulates in their immediate neighborhood. Synchrotron radiation UV
fluorescence microscopy is a new tool for assessment of antibiotic diffusion in
the endocarditis vegetation bacterial masses. 相似文献