Sodalis gen. nov. and Sodalis glossinidius sp. nov., a microaerophilic secondary endosymbiont of the tsetse fly Glossina morsitans morsitans.
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A secondary intracellular symbiotic bacterium was isolated from the haemolymph of the tsetse fly Glossina morsitans morsitans and cultured in Aedes albopictus cell line C6/36. Pure-culture isolation of this bacterium was achieved through the use of solid-phase culture under a microaerobic atmosphere. After isolation of strain M1T, a range of tests was performed to determine the phenotypic properties of this bacterium. Considering the results of these tests, along with the phylogenetic position of this micro-organism, it is proposed that this intracellular symbiont from G. m. morsitans should be classified in a new genus Sodalis gen. nov., as Sodalis glossinidius gen. nov., sp. nov. Strain M1T is the type strain for this new species. (+info)
Role of a novel photosystem II-associated carbonic anhydrase in photosynthetic carbon assimilation in Chlamydomonas reinhardtii.
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Intracellular carbonic anhydrases (CA) in aquatic photosynthetic organisms are involved in the CO2-concentrating mechanism (CCM), which helps to overcome CO2 limitation in the environment. In the green alga Chlamydomonas reinhardtii, this CCM is initiated and maintained by the pH gradient created across the chloroplast thylakoid membranes by photosystem (PS) II-mediated electron transport. We show here that photosynthesis is stimulated by a novel, intracellular alpha-CA bound to the chloroplast thylakoids. It is associated with PSII on the lumenal side of the thylakoid membranes. We demonstrate that PSII in association with this lumenal CA operates to provide an ample flux of CO2 for carboxylation. (+info)
Condensation of carbon in radioactive supernova gas.
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Chemistry resulting in the formation of large carbon-bearing molecules and dust in the interior of an expanding supernova was explored, and the equations governing their abundances were solved numerically. Carbon dust condenses from initially gaseous carbon and oxygen atoms because energetic electrons produced by radioactivity in the supernova cause dissociation of the carbon monoxide molecules, which would otherwise form and limit the supply of carbon atoms. The resulting free carbon atoms enable carbon dust to grow faster by carbon association than the rate at which the dust can be destroyed by oxidation. The origin of presolar micrometer-sized carbon solids that are found in meteorites is thereby altered. (+info)
Role of ArgR in activation of the ast operon, encoding enzymes of the arginine succinyltransferase pathway in Salmonella typhimurium.
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The ast operon, encoding enzymes of the arginine succinyltransferase (AST) pathway, was cloned from Salmonella typhimurium, and the nucleotide sequence for the upstream flanking region was determined. The control region contains several regulatory consensus sequences, including binding sites for NtrC, cyclic AMP receptor protein (CRP), and ArgR. The results of DNase I footprintings and gel retardation experiments confirm binding of these regulatory proteins to the identified sites. Exogenous arginine induced AST under nitrogen-limiting conditions, and this induction was abolished in an argR derivative. AST was also induced under carbon starvation conditions; this induction required functional CRP as well as functional ArgR. The combined data are consistent with the hypothesis that binding of one or more ArgR molecules to a region between the upstream binding sites for NtrC and CRP and two putative promoters plays a pivotal role in modulating expression of the ast operon in response to nitrogen or carbon limitation. (+info)
A small catalytic RNA motif with Diels-Alderase activity.
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BACKGROUND: The 'RNA world' hypothesis requires that RNA be able to catalyze a wide variety of chemical reactions. In vitro selection from combinatorial RNA libraries has been used to identify several catalytic activities, most of which have resulted in a self-modification of RNA at one of its constituents. The formation of carbon-carbon bonds is considered an essential prerequisite for a complex metabolism based on RNA. RESULTS: We describe the selection and characterization of new ribozymes that catalyze carbon-carbon bond formation by Diels-Alder reaction of a biotinylated maleimide with an RNA-tethered anthracene. Secondary structure analysis identified a 49-nucleotide RNA motif that accelerates the reaction about 20,000-fold. The motif has only 11 conserved nucleotides that are present in most of the selected sequences. The ribozyme motif is remarkably adaptable with respect to cofactor and metal-ion requirements. The motif was also re-engineered to give a 38-mer RNA that can act as a 'true' catalyst on short external substrate oligonucleotide-anthracene conjugates. CONCLUSIONS: We have identified a small, highly abundant RNA motif that can solve the complex task of forming two carbon-carbon bonds between two reactants in trans, a catalytic capacity useful for creating prebiotically relevant molecules. This is the smallest and fastest RNA catalyst for carbon-carbon bond formation reported to date. (+info)
Number and anatomical extent of lymph node metastases in gastric cancer: analysis using intra-lymph node injection of activated carbon particles (CH40).
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BACKGROUND: The long-term survival of 200 patients with gastric cancer who underwent radical gastrectomy was analyzed with respect to the number and anatomical extent of lymph node metastasis. All of the patients received intra-lymph node injection of fine activated carbon particle solution (CH40) during surgery. METHODS: The average number of resected lymph nodes increased in line with the anatomical level of lymph node dissection; 32.5 per patient in D1, 42.3 in D2, 3 and 66.3 in D4. The percentage of blackened lymph nodes without metastasis (42.4%) was slightly higher than that of lymph nodes containing metastasis (37.2%), but the difference was not statistically significant. Of the 200 patients, 61 (30.5%) had microscopic evidence of metastatic lymph node involvement. Twenty-two patients had between one and three metastatic lymph nodes, 19 had between four and nine and 20 patients had more than nine. The 5-year survival rate was 93.1% in patients without lymph node metastasis, 71.9% in patients with 1-8 metastatic nodes, 36.1% in patients with 4-9 nodes and 19.2% in patients with > 9 nodes. RESULTS: The 5-year survival rate according to the anatomical extent of metastatic lymph nodes was 93.1% in n0, 63.1% in n1, 37.9% in n2, 27.8% in n3 and 0% in n4. The number of metastatic lymph nodes and also their anatomical extent were identified as independent prognostic factors for survival by multivariate analysis. CONCLUSION: The number and anatomical extent of metastatic lymph nodes have similar impacts on prognosis in gastric cancer. (+info)
Acn9 is a novel protein of gluconeogenesis that is located in the mitochondrial intermembrane space.
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Previous studies have indicated that the Acn9 protein is involved in gluconeogenesis. Yeast mutants defective in the ACN9 gene display phenotypes identical with mutants defective in metabolic enzymes required for carbon assimilation. These phenotypes include the inability to utilize acetate as a carbon and energy source, elevated levels of enzymes of the glyoxylate cycle, gluconeogenesis and acetyl-CoA mobilization, and a deficiency in de novo synthesis of glucose from ethanol. The ACN9 gene was isolated by functional complementation of the acetate growth defect of an acn9 mutant. The open reading frame corresponds to YDR511w, and encodes a protein of unknown function. Homologs have been identified in human, mouse, and nematode databases. Two mutant alleles were sequenced. The mutations altered amino acid residues that are conserved among members of the new gene family. ACN9 gene expression was slightly repressed by glucose, and the level of the transcript was approximately 100-fold lower than that of glyoxylate or tricarboxylic acid cycle enzymes. A functional epitope-tagged form of Acn9 was expressed to study expression and the subcellular localization of the protein. The tagged protein was localized to the mitochondrial intermembrane space. (+info)
Carbon assimilation by Claviceps purpurea growing as a parasite.
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Carbon assimilation by Claviceps purpurea, growing as a parasite on cereals, has been investigated by supplying the host plant with 14CO2 in a closed system. The presence of the pathogen induced the plant to exude photosynthate which contained high levels of sucrose. During the period of 14CO2 supply, 14C was incorporated into the sucrose and so the path of carbon into the parasite could be traced. Hexoses, derived by the action of the fungal sucrase on sucrose, were assimilated by the pathogen and largely converted into polyols - mainly mannitol and, to a lesser extent, trehalose. The rate of carbohydrate metabolism decreased with maturation of the ergot, and also showed qualitative differences between the basal and apical regions of the ergot which were probably a function of nutrient supply. (+info)