共查询到20条相似文献,搜索用时 15 毫秒
1.
Background
The need for discovery of alternative, renewable, environmentally friendly energy sources and the development of cost-efficient, "clean" methods for their conversion into higher fuels becomes imperative. Ethanol, whose significance as fuel has dramatically increased in the last decade, can be produced from hexoses and pentoses through microbial fermentation. Importantly, plant biomass, if appropriately and effectively decomposed, is a potential inexpensive and highly renewable source of the hexose and pentose mixture. Recently, the engineered (to also catabolize pentoses) anaerobic bacterium Zymomonas mobilis has been widely discussed among the most promising microorganisms for the microbial production of ethanol fuel. However, Z. mobilis genome having been fully sequenced in 2005, there is still a small number of published studies of its in vivo physiology and limited use of the metabolic engineering experimental and computational toolboxes to understand its metabolic pathway interconnectivity and regulation towards the optimization of its hexose and pentose fermentation into ethanol. 相似文献2.
Background
Heliobacterium modesticaldum is a gram-positive nitrogen-fixing phototrophic bacterium that can grow either photoheterotrophically or chemotrophically but not photoautotrophically. Surprisingly, this organism is lacking only one gene for the complete reverse tricarboxylic acid (rTCA) cycle required for autotrophic carbon fixation. Along with the genomic information reported recently, we use multiple experimental approaches in this report to address questions regarding energy metabolic pathways in darkness, CO2 fixation, sugar assimilation and acetate metabolism. 相似文献3.
Orencio-Trejo M Flores N Escalante A Hernández-Chávez G Bolívar F Gosset G Martinez A 《Biotechnology for biofuels》2008,1(1):8
Background
A metabolic regulation study was performed, based upon measurements of enzymatic activities, fermentation performance, and RT-PCR analysis of pathways related to central carbon metabolism, in an ethanologenic Escherichia coli strain (CCE14) derived from lineage C. In comparison with previous engineered strains, this E coli derivative has a higher ethanol production rate in mineral medium, as a result of the elevated heterologous expression of the chromosomally integrated genes encoding PDC Zm and ADH Zm (pyruvate decarboxylase and alcohol dehydrogenase from Zymomonas mobilis). It is suggested that this behavior might be due to lineage differences between E. coli W and C. 相似文献4.
Background
Streptomyces coelicolor is a bacterium with a vast repertoire of metabolic functions and complex systems of cellular development. Its genome sequence is rich in genes that encode regulatory proteins to control these processes in response to its changing environment. We wished to apply a recently published bioinformatic method for identifying novel regulatory sequence signals to gain new insights into regulation in S. coelicolor. 相似文献5.
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Anette McLeod Monique Zagorec Marie-Christine Champomier-Vergès Kristine Naterstad Lars Axelsson 《BMC microbiology》2010,10(1):120
Background
Lactobacillus sakei is an important food-associated lactic acid bacterium commonly used as starter culture for industrial meat fermentation, and with great potential as a biopreservative in meat and fish products. Understanding the metabolic mechanisms underlying the growth performance of a strain to be used for food fermentations is important for obtaining high-quality and safe products. Proteomic analysis was used to study the primary metabolism in ten food isolates after growth on glucose and ribose, the main sugars available for L. sakei in meat and fish. 相似文献7.
Background
The gram-positive pathogenic bacterium Listeria monocytogenes is widely spread in the nature. L. monocytogenes was reported to be isolated from soil, water, sewage and sludge. Listeriolysin O (LLO) is a L. monocytogenes major virulence factor. In the course of infection in mammals, LLO is required for intracellular survival and apoptosis induction in lymphocytes. In this study, we explored the potential of LLO to promote interactions between L. monocytogenes and the ubiquitous inhabitant of natural ecosystems bacteriovorous free-living ciliate Tetrahymena pyriformis. 相似文献8.
Gaynor A Jenkins Marisol Figueira Gaurav A Kumar Wendy A Sweetman Katherine Makepeace Stephen I Pelton Richard Moxon Derek W Hood 《BMC microbiology》2010,10(1):48
Background
Sialic acid has been shown to be a major virulence determinant in the pathogenesis of otitis media caused by the bacterium Haemophilus influenzae. This study aimed to characterise the expression of genes required for the metabolism of sialic acid and to investigate the role of these genes in virulence. 相似文献9.
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Background
Nontypeable Haemophilus influenzae (NTHi) is a gram-negative bacterium that causes otitis media in children as well as other infections of the upper and lower respiratory tract in children and adults. We are employing genetic strategies to identify and characterize virulence determinants in NTHi. NTHi is naturally competent for transformation and thus construction of most mutants by common methodologies is relatively straightforward. However, new methodology was required in order to construct unmarked non-polar mutations in poorly expressed genes whose products are required for transformation. We have adapted the lambda red/FLP-recombinase-mediated strategy used in E. coli for use in NTHi. 相似文献12.
Torsten S Boutrup Kirsten Schauser Jørgen S Agerholm Tim K Jensen 《Acta veterinaria Scandinavica》2010,52(1):17
Background
Porcine proliferative enteropathy in pigs is caused by the obligate, intracellular bacterium Lawsonia intracellularis. In vitro studies have shown close bacterium-cell interaction followed by cellular uptake of the bacterium within 3 h post inoculation (PI). However, knowledge of the initial in vivo interaction between porcine intestinal epithelium and the bacterium is limited. The aims of the present study were to evaluate the usefulness of a ligated small intestinal loop model to study L. intracellularis infections and to obtain information on the very early L. intracellularis-enterocyte interactions. 相似文献13.
Li Y Tschaplinski TJ Engle NL Hamilton CY Rodriguez M Liao JC Schadt CW Guss AM Yang Y Graham DE 《Biotechnology for biofuels》2012,5(1):2
Background
The model bacterium Clostridium cellulolyticum efficiently degrades crystalline cellulose and hemicellulose, using cellulosomes to degrade lignocellulosic biomass. Although it imports and ferments both pentose and hexose sugars to produce a mixture of ethanol, acetate, lactate, H2 and CO2, the proportion of ethanol is low, which impedes its use in consolidated bioprocessing for biofuels production. Therefore genetic engineering will likely be required to improve the ethanol yield. Plasmid transformation, random mutagenesis and heterologous expression systems have previously been developed for C. cellulolyticum, but targeted mutagenesis has not been reported for this organism, hindering genetic engineering. 相似文献14.
Background
Enzymes involved in DNA metabolic events of the highly radioresistant bacterium Deinococcus radiodurans are currently examined to understand the mechanisms that protect and repair the Deinococcus radiodurans genome after extremely high doses of γ-irradiation. Although several Deinococcus radiodurans DNA repair enzymes have been characterised, no biochemical data is available for DNA ligation and DNA endhealing enzymes of Deinococcus radiodurans so far. DNA ligases are necessary to seal broken DNA backbones during replication, repair and recombination. In addition, ionizing radiation frequently leaves DNA strand-breaks that are not feasible for ligation and thus require end-healing by a 5'-polynucleotide kinase or a 3'-phosphatase. We expect that DNA ligases and end-processing enzymes play an important role in Deinococcus radiodurans DNA strand-break repair. 相似文献15.
A. A. De Graaf Katharina Striegel Rolf M. Wittig Birgit Laufer Günter Schmitz Wolfgang Wiechert Georg A. Sprenger Hermann Sahm 《Archives of microbiology》1999,171(6):371-385
The reasons for the well-known significantly different behaviour of the anaerobic, gram-negative, ethanologenic bacterium
Zymomonas mobilis during growth on fructose (i.e. decreased growth and ethanol yields, increased by-product formation) as compared to that
on its second natural substrate, glucose, have remained unexplained. A xylose-fermenting recombinant strain of Z. mobilis that was recently constructed in our laboratory also unexpectedly displayed an increased formation of by-products and a strongly
reduced growth rate as compared to the parent strain. Therefore, a comprehensive study employing recently developed NMR-based
methods for the in vivo analysis of intracellular phosphorylated pool sizes and metabolic fluxes was undertaken to enable
a global characterization of the intracellular metabolic state of Z. mobilis during growth on 13C-labelled glucose, fructose and xylose in defined continuous cultures. The 13C-NMR flux analysis indicated that ribose 5-phosphate is synthesized via the nonoxidative pentose phosphate pathway in Z. mobilis, and it identified a metabolic bottleneck in the recombinant xylose-fermenting Z. mobilis strain at the level of heterologous xylulokinase. The 31P-NMR analyses revealed a global alteration of the levels of intracellular phosphorylated metabolites during growth on fructose
as compared to that on glucose. The results suggest that this is primarily caused by an elevated concentration of intracellular
fructose 6-phosphate.
Received: 7 January 1999 / Accepted: 22 March 1999 相似文献
16.
Joseph Horzempa Paul E CarlsonJr Dawn M O'Dee Robert MQ Shanks Gerard J Nau 《BMC microbiology》2008,8(1):172
Background
After infecting a mammalian host, the facultative intracellular bacterium,Francisella tularensis, encounters an elevated environmental temperature. We hypothesized that this temperature change may regulate genes essential for infection. 相似文献17.
Hiraku Sasaki Hiroki Ishikawa Toru Sato Satoshi Sekiguchi Hiromi Amao Eiichi Kawamoto Tetsuya Matsumoto Kazuhiko Shirama 《BMC microbiology》2011,11(1):55
Background
Pasteurella pneumotropica is a ubiquitous bacterium that is frequently isolated from laboratory rodents and causes various clinical symptoms in immunodeficient animals. Currently two RTX toxins, PnxIA and PnxIIA, which are similar to hemolysin-like high-molecular-weight exoproteins are known in this species. In this study, we identified and analyzed a further RTX toxin named PnxIIIA and the corresponding type I secretion system. 相似文献18.
This research was designed to maximize ethanol production from a glucose-xylose sugar mixture (simulating a sugar cane bagasse
hydrolysate) by co-fermentation with Zymomonas mobilis and Pachysolen tannophilus. The volumetric ethanol productivity of Z. mobilis with 50 g glucose/l was 2.87 g/l/h, giving an ethanol yield of 0.50 g/g glucose, which is 98% of the theoretical. P. tannophilus when cultured on 50 g xylose/l gave a volumetric ethanol productivity of 0.10 g/l/h with an ethanol yield of 0.15 g/g xylose,
which is 29% of the theoretical. On optimization of the co-fermentation with the sugar mixture (60 g glucose/l and 40 g xylose/l)
a total ethanol yield of 0.33 g/g sugar mixture, which is 65% of the theoretical yield, was obtained. The co-fermentation
increased the ethanol yield from xylose to 0.17 g/g. Glucose and xylose were completely utilized and no residual sugar was
detected in the medium at the end of the fermentation. The pH of the medium was found to be a good indicator of the fermentation
status. The optimum conditions were a temperature of 30°C, initial inoculation with Z. mobilis and incubation with no aeration, inactivation of bacterium after the utilization of glucose, followed by inoculation with
P. tannophilus and incubation with limited aeration. 相似文献
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