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Search Results: 1 - 10 of 18720 matches for " Andrew WB Johnston "
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The genome of Rhizobium leguminosarum has recognizable core and accessory components
J Peter W Young, Lisa C Crossman, Andrew WB Johnston, Nicholas R Thomson, Zara F Ghazoui, Katherine H Hull, Margaret Wexler, Andrew RJ Curson, Jonathan D Todd, Philip S Poole, Tim H Mauchline, Alison K East, Michael A Quail, Carol Churcher, Claire Arrowsmith, Inna Cherevach, Tracey Chillingworth, Kay Clarke, Ann Cronin, Paul Davis, Audrey Fraser, Zahra Hance, Heidi Hauser, Kay Jagels, Sharon Moule, Karen Mungall, Halina Norbertczak, Ester Rabbinowitsch, Mandy Sanders, Mark Simmonds, Sally Whitehead, Julian Parkhill
Genome Biology , 2006, DOI: 10.1186/gb-2006-7-4-r34
Abstract: The 7.75 Mb genome comprises a circular chromosome and six circular plasmids, with 61% G+C overall. All three rRNA operons and 52 tRNA genes are on the chromosome; essential protein-encoding genes are largely chromosomal, but most functional classes occur on plasmids as well. Of the 7,263 protein-encoding genes, 2,056 had orthologs in each of three related genomes (Agrobacterium tumefaciens, Sinorhizobium meliloti, and Mesorhizobium loti), and these genes were over-represented in the chromosome and had above average G+C. Most supported the rRNA-based phylogeny, confirming A. tumefaciens to be the closest among these relatives, but 347 genes were incompatible with this phylogeny; these were scattered throughout the genome but were over-represented on the plasmids. An unexpectedly large number of genes were shared by all three rhizobia but were missing from A. tumefaciens.Overall, the genome can be considered to have two main components: a 'core', which is higher in G+C, is mostly chromosomal, is shared with related organisms, and has a consistent phylogeny; and an 'accessory' component, which is sporadic in distribution, lower in G+C, and located on the plasmids and chromosomal islands. The accessory genome has a different nucleotide composition from the core despite a long history of coexistence.The symbiosis between legumes and N2-fixing bacteria (rhizobia) is of huge agronomic benefit, allowing many crops to be grown without N fertilizer. It is a sophisticated example of coupled development between bacteria and higher plants, culminating in the organogenesis of root nodules [1]. There have been many genetic analyses of rhizobia, notably of Sinorhizobium meliloti (the symbiont of alfalfa), Bradyrhizobium japonicum (soybean), and Rhizobium leguminosarum, which has biovars that nodulate peas and broad beans (biovar viciae), clovers (biovar trifolii), or kidney beans (biovar phaseoli).The Rhizobiales, an α-proteobacterial order that also includes mammalian pathogens B
Homology manifold bordism
Heather Johnston,Andrew Ranicki
Mathematics , 1999,
Abstract: The Bryant-Ferry-Mio-Weinberger surgery exact sequence for high-dimensional compact ANR homology manifolds is used to obtain transversality, splitting and bordism results for homology manifolds, generalizing previous work of Johnston.
The Redox System in C. elegans, a Phylogenetic Approach
Andrew D. Johnston,Paul R. Ebert
Journal of Toxicology , 2012, DOI: 10.1155/2012/546915
Abstract: Oxidative stress is a toxic state caused by an imbalance between the production and elimination of reactive oxygen species (ROS). ROS cause oxidative damage to cellular components such as proteins, lipids, and nucleic acids. While the role of ROS in cellular damage is frequently all that is noted, ROS are also important in redox signalling. The “Redox Hypothesis" has been proposed to emphasize a dual role of ROS. This hypothesis suggests that the primary effect of changes to the redox state is modified cellular signalling rather than simply oxidative damage. In extreme cases, alteration of redox signalling can contribute to the toxicity of ROS, as well as to ageing and age-related diseases. The nematode species Caenorhabditis elegans provides an excellent model for the study of oxidative stress and redox signalling in animals. We use protein sequences from central redox systems in Homo sapiens, Drosophila melanogaster, and Saccharomyces cerevisiae to query Genbank for homologous proteins in C. elegans. We then use maximum likelihood phylogenetic analysis to compare protein families between C. elegans and the other organisms to facilitate future research into the genetics of redox biology. 1. Introduction Molecular oxygen is necessary for the survival of most complex multicellular organisms. The necessity of oxygen comes from its role in aerobic respiration, a process of extracting energy from food that is approximately 19 times more efficient than its anaerobic counterpart. In eukaryotes, aerobic respiration is carried out in the mitochondria (descendant of an aerobically respiring bacterium) by a series of electron transfer reactions that are coupled to the generation of a proton gradient. This proton gradient is used to generate the cellular fuel adenosine triphosphate (ATP). The residual energy of the spent electrons is consumed in the reduction of molecular oxygen (O2) to water (H2O). Aerobic respiration cannot occur without this last step, but the reliance on oxygen as the final electron acceptor poses a continual threat of oxidative damage to aerobically respiring organisms. The threat posed by oxygen comes largely from its conversion to the free radical superoxide ( O 2 ? ? ) rather than water [1]. Superoxide is a highly reactive short-lived ROS. Detoxification of superoxide and other ROS is performed by antioxidants, which convert ROS to less reactive molecules. The antioxidant enzyme superoxide dismutase (SOD) converts superoxide to water and hydrogen peroxide (H2O2), which is another ROS and a potent oxidising agent (see Figure 1) [2]. Under
[3S*,5S*,6S*]-1,7-Dioxaspiro[5.5]undecane-3,5-diyl Diacetate
Margaret A. Brimble,Andrew D. Johnston
Molecules , 1997, DOI: 10.3390/m22
Abstract: No abstract available
Margaret A. Brimble,Andrew D. Johnston
Molecules , 1997, DOI: 10.3390/m15
Abstract: No abstract available
[3R*,5S*,6S*]-5-Hydroxy-1,7-dioxaspiro[5.5]undec-3-yl 3,5-Dinitrobenzoate
Margaret A. Brimble,Andrew D. Johnston
Molecules , 1997, DOI: 10.3390/m17
Abstract: No abstract available
Margaret A. Brimble,Andrew D. Johnston
Molecules , 1997, DOI: 10.3390/m16
Abstract: No abstract available
Margaret A. Brimble,Andrew D. Johnston
Molecules , 1997, DOI: 10.3390/m20
Abstract: No abstract available
[3R*,5S*,6S*]-1,7-Dioxaspiro[5.5]undecane-3,5-diyl Bis(3,5-dinitrobenzoate)
Margaret A. Brimble,Andrew D. Johnston
Molecules , 1997, DOI: 10.3390/m18
Abstract: No abstract available
Margaret A Brimble,Andrew D Johnston
Molecules , 1997, DOI: 10.3390/m19
Abstract: No abstract available
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