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Most microorganisms can metabolize glycerol when external electron acceptors are available (i.e. under respiratory conditions). However, few can do so under fermentative conditions owing to the unique redox constraints imposed by the high degree of reduction of glycerol. Here, we utilize in silico analysis combined with in vivo genetic and biochemical approaches to investigate the fermentative metabolism of glycerol in Escherichia coli. We found that E. coli can achieve redox balance at alkaline pH by reducing protons to H2, complementing the previously reported role of 1,2-propanediol synthesis under acidic conditions. In this new redox balancing mode, H2 evolution is coupled to a respiratory glycerol dissimilation pathway composed of glycerol kinase (GK) and glycerol-3-phosphate (G3P) dehydrogenase (G3PDH). GK activates glycerol to G3P, which is further oxidized by G3PDH to generate reduced quinones that drive hydrogenase-dependent H2 evolution. Despite the importance of the GK-G3PDH route under alkaline conditions, we found that the NADH-generating glycerol dissimilation pathway via glycerol dehydrogenase (GldA) and phosphoenolpyruvate (PEP)-dependent dihydroxyacetone kinase (DHAK) was essential under both alkaline and acidic conditions. We assessed system-wide metabolic impacts of the constraints imposed by the PEP dependency of the GldA-DHAK route. This included the identification of enzymes and pathways that were not previously known to be involved in glycerol metabolisms such as PEP carboxykinase, PEP synthetase, multiple fructose-1,6-bisphosphatases and the fructose phosphate bypass. 相似文献
243.
Symplocos saxatilis (Symplocaceae), a new dioecious species from Serra do Cipó, Minas Gerais, Brazil
João Luiz M. Aranha Filho Peter W. Fritsch Frank Almeda Angela B. Martins 《Brittonia》2007,59(3):233-237
Symplocos saxatilis from Serra do Cipó, Minas Gerais State, Brazil, is newly described and illustrated on the basis of field and herbarium studies.
It appears to be restricted to “campo rupestre” (rocky field) habitats. This new species is characterized by its 1- to 3-flowered
pedunculate inflorescence, 11 to 14 staminodes of the pistillate flowers, and 0.7–1.5 mm thick endocarp. 相似文献
244.
Processes maintaining protein homeostasis in the cell are governed by the activities of molecular chaperones that mainly assist in the folding of polypeptide chains and by a large class of proteases that regulate protein levels through degradation. ClpP proteases define a distinctive family of cylindrical, energy-dependent serine proteases that are highly conserved throughout bacteria and eukaryota. They typically interact with ATP-dependent AAA+ chaperones that bind and unfold target substrates and then translocate them into ClpP for degradation. Structural and functional studies have provided a detailed view of the mechanism of function of this class of proteases. 相似文献
245.
Mutations in the zebrafish connexin43 (cx43) gene cause the short fin phenotype, indicating that direct cell-cell communication contributes to bone length. Three independently generated cx43 alleles exhibit short segments of variable sizes, suggesting that gap junctional intercellular communication may regulate bone growth. Dye coupling assays showed that all alleles are capable of forming gap junction channels. However, ionic coupling assays revealed allele-specific differences in coupling efficiency and gating. For instance, oocyte pairs expressing the weakest allele exhibited much higher levels of coupling than either of the strong alleles. Therefore, measurable differences in Cx43 function may be correlated with the severity of defects in bone length. 相似文献
246.
Patterns of sequence variability and divergence at the diminutive gene region of Drosophila melanogaster: complex patterns suggest an ancestral selective sweep 总被引:1,自引:0,他引:1 下载免费PDF全文
To identify putatively swept regions of the Drosophila melanogaster genome, we performed a microsatellite screen spanning a 260-kb region of the X chromosome in populations from Zimbabwe, Ecuador, the United States, and China. Among the regions identified by this screen as showing a complex pattern of reduced heterozygosity and a skewed frequency spectrum was the gene diminutive (dm). To investigate the microsatellite findings, nucleotide sequence polymorphism data were generated in populations from both China and Zimbabwe spanning a 25-kb region and encompassing dm. Analysis of the sequence data reveals strongly reduced nucleotide variation across the entire gene region in both the non-African and the African populations, an extended haplotype pattern, and structured linkage disequilibrium, as well as a rejection of neutrality in favor of selection using a composite likelihood-ratio test. Additionally, unusual patterns of synonymous site evolution were observed at the second exon of this locus. On the basis of simulation studies as well as recently proposed methods for distinguishing between selection and nonequilibrium demography, we find that this "footprint" is best explained by a selective sweep in the ancestral population, the signal of which has been somewhat blurred via founder effects in the non-African samples. 相似文献
247.
Requirements of eliminating animal proteins from cell culture have intensified in recent years, with the pressure of regulatory agencies related to biopharmaceuticals production. In this work, the substitution of fetal bovine serum by yeastolate and a soy hydrolysate (Hy Soy) for the culture of Drosophila melanogaster Schneider 2 cells transfected for the production of rabies virus G glycoprotein was evaluated. TC100 supplemented with glucose, glutamine, lipid emulsion and Pluronic F68 was employed as basal medium. Results show that yeastolate was more efficient on cell growth stimulation than Hy Soy. Cells adapted in medium formulation supplemented with 3 g/L yeastolate, 1% lipid emulsion, 10 g/L glucose, 3.5 g/L glutamine and 0.1% Pluronic F68 attained a maximum concentration of 10.7 x 10(6) cells/mL, with the expression of 9.4 ng/mL G glycoprotein. 相似文献
248.
McTiernan A Sorensen B Irwin ML Morgan A Yasui Y Rudolph RE Surawicz C Lampe JW Lampe PD Ayub K Potter JD 《Obesity (Silver Spring, Md.)》2007,15(6):1496-1512
Objectives: The effect of national exercise recommendations on adiposity is unknown and may differ by sex. We examined long‐term effects of aerobic exercise on adiposity in women and men. Research Methods and Procedures: This was a 12‐month randomized, controlled clinical trial testing exercise effect on weight and body composition in men (N = 102) and women (N = 100). Sedentary/unfit persons, 40 to 75 years old, were recruited through physician practices and media. The intervention was facility‐ and home‐based moderate‐to‐vigorous intensity aerobic activity, 60 min/d, 6 days/wk vs. controls (no intervention). Results: Exercisers exercised a mean 370 min/wk (men) and 295 min/wk (women), and seven dropped the intervention. Exercisers lost weight (women, ?1.4 vs. +0.7 kg in controls, p = 0.008; men, ?1.8 vs. ?0.1 kg in controls, p = 0.03), BMI (women, ?0.6 vs. +0.3 kg/m2 in controls, p = 0.006; men, ?0.5 kg/m2 vs. no change in controls, p = 0.03), waist circumference (women, ?1.4 vs. +2.2 cm in controls, p < 0.001; men, ?3.3 vs. ?0.4 cm in controls, p = 0.003), and total fat mass (women, ?1.9 vs. +0.2 kg in controls, p = 0.001; men, ?3.0 vs. +0.2 kg in controls, p < 0.001). Exercisers with greater increases in pedometer‐measured steps per day had greater decreases in weight, BMI, body fat, and intra‐abdominal fat (all p trend < 0.05 in both men and women). Similar trends were observed for increased minutes per day of exercise and for increases in maximal oxygen consumption. Discussion: These data support the U.S. Department of Agriculture and Institute of Medicine guidelines of 60 min/d of moderate‐to‐vigorous physical activity. 相似文献
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Alexander Bürkle Graziella Caselli Claudio Franceschi Erminia Mariani Paolo Sansoni Angela Santoni Giancarlo Vecchio Jacek M Witkowski Calogero Caruso 《Immunity & ageing : I & A》2007,4(1):4-8
On April 18, 2007 an international meeting on Pathophysiology of Ageing, Longevity and Age-Related Diseases was held in Palermo,
Italy. Several interesting topics on Cancer, Immunosenescence, Age-related inflammatory diseases and longevity were discussed.
In this report we summarize the most important issues. However, ageing must be considered an unavoidable end point of the
life history of each individual, nevertheless the increasing knowledge on ageing mechanisms, allows envisaging many different
strategies to cope with, and delay it. So, a better understanding of pathophysiology of ageing and age-related disease is
essential for giving everybody a reasonable chance for living a long and enjoyable final part of the life. 相似文献