<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Coppi, Maddalena V</style></author><author><style face="normal" font="default" size="100%">O'Neil, Regina A</style></author><author><style face="normal" font="default" size="100%">Leang, Ching</style></author><author><style face="normal" font="default" size="100%">Kaufmann, Franz</style></author><author><style face="normal" font="default" size="100%">Methé, Barbara A</style></author><author><style face="normal" font="default" size="100%">Nevin, Kelly P</style></author><author><style face="normal" font="default" size="100%">Woodard, Trevor L</style></author><author><style face="normal" font="default" size="100%">Liu, Anna</style></author><author><style face="normal" font="default" size="100%">Lovley, Derek R</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Involvement of Geobacter sulfurreducens SfrAB in acetate metabolism rather than intracellular, respiration-linked Fe(III) citrate reduction.</style></title><secondary-title><style face="normal" font="default" size="100%">Microbiology</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Microbiology (Reading, Engl.)</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Acetates</style></keyword><keyword><style  face="normal" font="default" size="100%">Amino Acid Transport Systems</style></keyword><keyword><style  face="normal" font="default" size="100%">Bacterial Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Cell Membrane</style></keyword><keyword><style  face="normal" font="default" size="100%">Citric Acid Cycle</style></keyword><keyword><style  face="normal" font="default" size="100%">Cytoplasm</style></keyword><keyword><style  face="normal" font="default" size="100%">Energy Metabolism</style></keyword><keyword><style  face="normal" font="default" size="100%">Ferric Compounds</style></keyword><keyword><style  face="normal" font="default" size="100%">Formic Acids</style></keyword><keyword><style  face="normal" font="default" size="100%">Fumarates</style></keyword><keyword><style  face="normal" font="default" size="100%">Gene Deletion</style></keyword><keyword><style  face="normal" font="default" size="100%">Gene Expression Profiling</style></keyword><keyword><style  face="normal" font="default" size="100%">Geobacter</style></keyword><keyword><style  face="normal" font="default" size="100%">Hydrogen</style></keyword><keyword><style  face="normal" font="default" size="100%">NADH, NADPH Oxidoreductases</style></keyword><keyword><style  face="normal" font="default" size="100%">Oligonucleotide Array Sequence Analysis</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2007</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2007 Oct</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">153</style></volume><pages><style face="normal" font="default" size="100%">3572-85</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A soluble ferric reductase, SfrAB, which catalysed the NADPH-dependent reduction of chelated Fe(III), was previously purified from the dissimilatory Fe(III)-reducing micro-organism Geobacter sulfurreducens, suggesting that reduction of chelated forms of Fe(III) might be cytoplasmic. However, metabolically active spheroplast suspensions could not catalyse acetate-dependent Fe(III) citrate reduction, indicating that periplasmic and/or outer-membrane components were required for Fe(III) citrate reduction. Furthermore, phenotypic analysis of an SfrAB knockout mutant suggested that SfrAB was involved in acetate metabolism rather than respiration-linked Fe(III) reduction. The mutant could not grow via the reduction of either Fe(III) citrate or fumarate when acetate was the electron donor but could grow with either acceptor if either hydrogen or formate served as the electron donor. Following prolonged incubation in acetate : fumarate medium in the absence of hydrogen and formate, an 'acetate-adapted' SfrAB-null strain was isolated that was capable of growth on acetate : fumarate medium but not acetate : Fe(III) citrate medium. Comparison of gene expression in this strain with that of the wild-type revealed upregulation of a potential NADPH-dependent ferredoxin oxidoreductase as well as genes involved in energy generation and amino acid uptake, suggesting that NADPH homeostasis and the tricarboxylic acid (TCA) cycle were perturbed in the 'acetate-adapted' SfrAB-null strain. Membrane and soluble fractions prepared from the 'acetate-adapted' strain were depleted of NADPH-dependent Fe(III), viologen and quinone reductase activities. These results indicate that cytoplasmic, respiration-linked reduction of Fe(III) by SfrAB in vivo is unlikely and suggest that deleting SfrAB may interfere with growth via acetate oxidation by interfering with NADP regeneration.</style></abstract><issue><style face="normal" font="default" size="100%">Pt 10</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/17906154?dopt=Abstract</style></custom1></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Chapelle, Francis H</style></author><author><style face="normal" font="default" size="100%">O'Neill, Kathleen</style></author><author><style face="normal" font="default" size="100%">Bradley, Paul M</style></author><author><style face="normal" font="default" size="100%">Methé, Barbara A</style></author><author><style face="normal" font="default" size="100%">Ciufo, Stacy A</style></author><author><style face="normal" font="default" size="100%">Knobel, LeRoy L</style></author><author><style face="normal" font="default" size="100%">Lovley, Derek R</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">A hydrogen-based subsurface microbial community dominated by methanogens.</style></title><secondary-title><style face="normal" font="default" size="100%">Nature</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Nature</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Bacteria</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA, Archaeal</style></keyword><keyword><style  face="normal" font="default" size="100%">DNA, Bacterial</style></keyword><keyword><style  face="normal" font="default" size="100%">Ecosystem</style></keyword><keyword><style  face="normal" font="default" size="100%">Euryarchaeota</style></keyword><keyword><style  face="normal" font="default" size="100%">Exobiology</style></keyword><keyword><style  face="normal" font="default" size="100%">Hydrogen</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Sequence Data</style></keyword><keyword><style  face="normal" font="default" size="100%">Phylogeny</style></keyword><keyword><style  face="normal" font="default" size="100%">RNA, Ribosomal, 16S</style></keyword><keyword><style  face="normal" font="default" size="100%">Water Microbiology</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2002</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2002 Jan 17</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">415</style></volume><pages><style face="normal" font="default" size="100%">312-5</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The search for extraterrestrial life may be facilitated if ecosystems can be found on Earth that exist under conditions analogous to those present on other planets or moons. It has been proposed, on the basis of geochemical and thermodynamic considerations, that geologically derived hydrogen might support subsurface microbial communities on Mars and Europa in which methanogens form the base of the ecosystem. Here we describe a unique subsurface microbial community in which hydrogen-consuming, methane-producing Archaea far outnumber the Bacteria. More than 90% of the 16S ribosomal DNA sequences recovered from hydrothermal waters circulating through deeply buried igneous rocks in Idaho are related to hydrogen-using methanogenic microorganisms. Geochemical characterization indicates that geothermal hydrogen, not organic carbon, is the primary energy source for this methanogen-dominated microbial community. These results demonstrate that hydrogen-based methanogenic communities do occur in Earth's subsurface, providing an analogue for possible subsurface microbial ecosystems on other planets.</style></abstract><issue><style face="normal" font="default" size="100%">6869</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/11797006?dopt=Abstract</style></custom1></record></records></xml>