<?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%">Kashefi, K</style></author><author><style face="normal" font="default" size="100%">Moskowitz, B M</style></author><author><style face="normal" font="default" size="100%">Lovley, D R</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Characterization of extracellular minerals produced during dissimilatory Fe(III) and U(VI) reduction at 100 degrees C by Pyrobaculum islandicum.</style></title><secondary-title><style face="normal" font="default" size="100%">Geobiology</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Geobiology</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Ferric Compounds</style></keyword><keyword><style  face="normal" font="default" size="100%">Ferumoxytol</style></keyword><keyword><style  face="normal" font="default" size="100%">Hot Temperature</style></keyword><keyword><style  face="normal" font="default" size="100%">Hydrogen</style></keyword><keyword><style  face="normal" font="default" size="100%">Minerals</style></keyword><keyword><style  face="normal" font="default" size="100%">Oxidation-Reduction</style></keyword><keyword><style  face="normal" font="default" size="100%">Pyrobaculum</style></keyword><keyword><style  face="normal" font="default" size="100%">Uranium</style></keyword><keyword><style  face="normal" font="default" size="100%">X-Ray Diffraction</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2008</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2008 Mar</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">6</style></volume><pages><style face="normal" font="default" size="100%">147-54</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In order to gain insight into the significance of biotic metal reduction and mineral formation in hyperthermophilic environments, metal mineralization as a result of the dissimilatory reduction of poorly crystalline Fe(III) oxide, and U(VI) reduction at 100 degrees C by Pyrobaculum islandicum was investigated. When P. islandicum was grown in a medium with poorly crystalline Fe(III) oxide as an electron acceptor and hydrogen as an electron donor, the Fe(III) oxide was reduced to an extracellular, ultrafine-grained magnetite with characteristics similar to that found in some hot environments and that was previously thought to be of abiotic origin. Furthermore, cell suspensions of P. islandicum rapidly reduced the soluble and oxidized form of uranium, U(VI), to extracellular precipitates of the highly insoluble U(IV) mineral, uraninite (UO(2)). The reduction of U(VI) was dependent on the presence of hydrogen as the electron donor. These findings suggest that microbes may play a key role in metal deposition in hyperthermophilic environments and provide a plausible explanation for such phenomena as magnetite accumulation and formation of uranium deposits at ca. 100 degrees C.</style></abstract><issue><style face="normal" font="default" size="100%">2</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/18380877?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%">Feinberg, Lawrence F</style></author><author><style face="normal" font="default" size="100%">Srikanth, R</style></author><author><style face="normal" font="default" size="100%">Vachet, Richard W</style></author><author><style face="normal" font="default" size="100%">Holden, James F</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Constraints on anaerobic respiration in the hyperthermophilic Archaea Pyrobaculum islandicum and Pyrobaculum aerophilum.</style></title><secondary-title><style face="normal" font="default" size="100%">Appl Environ Microbiol</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Appl. Environ. Microbiol.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Anaerobiosis</style></keyword><keyword><style  face="normal" font="default" size="100%">FMN Reductase</style></keyword><keyword><style  face="normal" font="default" size="100%">Hydrogen-Ion Concentration</style></keyword><keyword><style  face="normal" font="default" size="100%">Iron</style></keyword><keyword><style  face="normal" font="default" size="100%">Nitrates</style></keyword><keyword><style  face="normal" font="default" size="100%">Oxidation-Reduction</style></keyword><keyword><style  face="normal" font="default" size="100%">Pyrobaculum</style></keyword><keyword><style  face="normal" font="default" size="100%">Species Specificity</style></keyword><keyword><style  face="normal" font="default" size="100%">Sulfur</style></keyword><keyword><style  face="normal" font="default" size="100%">Sulfurtransferases</style></keyword><keyword><style  face="normal" font="default" size="100%">Thiosulfates</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2008</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2008 Jan</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">74</style></volume><pages><style face="normal" font="default" size="100%">396-402</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;Pyrobaculum islandicum uses iron, thiosulfate, and elemental sulfur for anaerobic respiration, while Pyrobaculum aerophilum uses iron and nitrate; however, the constraints on these processes and their physiological mechanisms for iron and sulfur reduction are not well understood. Growth rates on sulfur compounds are highest at pH 5 to 6 and highly reduced (&lt;-420-mV) conditions, while growth rates on nitrate and iron are highest at pH 7 to 9 and more-oxidized (&gt;-210-mV) conditions. Growth on iron expands the known pH range of growth for both organisms. P. islandicum differs from P. aerophilum in that it requires direct contact with insoluble iron oxide for growth, it did not produce any extracellular compounds when grown on insoluble iron, and it lacked 2,6-anthrahydroquinone disulfonate oxidase activity. Furthermore, iron reduction in P. islandicum appears to be completely independent of c-type cytochromes. Like that in P. aerophilum, NADH-dependent ferric reductase activity in P. islandicum increased significantly in iron-grown cultures relative to that in non-iron-grown cultures. Proteomic analyses showed that there were significant increases in the amounts of a putative membrane-bound thiosulfate reductase in P. islandicum cultures grown on thiosulfate relative to those in cultures grown on iron and elemental sulfur. This is the first evidence of this enzyme being used in either a hyperthermophile or an archaeon. Pyrobaculum arsenaticum and Pyrobaculum calidifontis also grew on Fe(III) citrate and insoluble iron oxide, but only P. arsenaticum could grow on insoluble iron without direct contact.&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">2</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/18039820?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%">Yennaco, Lynda J</style></author><author><style face="normal" font="default" size="100%">Hu, Yajing</style></author><author><style face="normal" font="default" size="100%">Holden, James F</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Characterization of malate dehydrogenase from the hyperthermophilic archaeon Pyrobaculum islandicum.</style></title><secondary-title><style face="normal" font="default" size="100%">Extremophiles</style></secondary-title><alt-title><style face="normal" font="default" size="100%">Extremophiles</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Citric Acid Cycle</style></keyword><keyword><style  face="normal" font="default" size="100%">Hydrogen-Ion Concentration</style></keyword><keyword><style  face="normal" font="default" size="100%">Kinetics</style></keyword><keyword><style  face="normal" font="default" size="100%">Malate Dehydrogenase</style></keyword><keyword><style  face="normal" font="default" size="100%">Malates</style></keyword><keyword><style  face="normal" font="default" size="100%">Molecular Weight</style></keyword><keyword><style  face="normal" font="default" size="100%">NAD</style></keyword><keyword><style  face="normal" font="default" size="100%">NADP</style></keyword><keyword><style  face="normal" font="default" size="100%">Oxaloacetic Acid</style></keyword><keyword><style  face="normal" font="default" size="100%">Phylogeny</style></keyword><keyword><style  face="normal" font="default" size="100%">Protein Conformation</style></keyword><keyword><style  face="normal" font="default" size="100%">Protein Subunits</style></keyword><keyword><style  face="normal" font="default" size="100%">Pyrobaculum</style></keyword><keyword><style  face="normal" font="default" size="100%">Recombinant Proteins</style></keyword><keyword><style  face="normal" font="default" size="100%">Sequence Analysis, Protein</style></keyword><keyword><style  face="normal" font="default" size="100%">Substrate Specificity</style></keyword><keyword><style  face="normal" font="default" size="100%">Temperature</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 Sep</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">11</style></volume><pages><style face="normal" font="default" size="100%">741-6</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;Native and recombinant malate dehydrogenase (MDH) was characterized from the hyperthermophilic, facultatively autotrophic archaeon Pyrobaculum islandicum. The enzyme is a homotetramer with a subunit mass of 33 kDa. The activity kinetics of the native and recombinant proteins are the same. The apparent K ( m ) values of the recombinant protein for oxaloacetate (OAA) and NADH (at 80 degrees C and pH 8.0) were 15 and 86 microM, respectively, with specific activity as high as 470 U mg(-1). Activity decreased more than 90% when NADPH was used. The catalytic efficiency of OAA reduction by P. islandicum MDH using NADH was significantly higher than that reported for any other archaeal MDH. Unlike other archaeal MDHs, specific activity of the P. islandicum MDH back-reaction also decreased more than 90% when malate and NAD(+) were used as substrates and was not detected with NADP(+). A phylogenetic tree of 31 archaeal MDHs shows that they fall into 5 distinct groups separated largely along taxonomic lines suggesting minimal lateral mdh transfer between Archaea.&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">5</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/17487443?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%">Feinberg, Lawrence F</style></author><author><style face="normal" font="default" size="100%">Holden, James F</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Characterization of dissimilatory Fe(III) versus NO3- reduction in the hyperthermophilic archaeon Pyrobaculum aerophilum.</style></title><secondary-title><style face="normal" font="default" size="100%">J Bacteriol</style></secondary-title><alt-title><style face="normal" font="default" size="100%">J. Bacteriol.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Cytochromes c</style></keyword><keyword><style  face="normal" font="default" size="100%">Ferric Compounds</style></keyword><keyword><style  face="normal" font="default" size="100%">FMN Reductase</style></keyword><keyword><style  face="normal" font="default" size="100%">Hot Temperature</style></keyword><keyword><style  face="normal" font="default" size="100%">NAD</style></keyword><keyword><style  face="normal" font="default" size="100%">Nitrates</style></keyword><keyword><style  face="normal" font="default" size="100%">Oxidation-Reduction</style></keyword><keyword><style  face="normal" font="default" size="100%">Pyrobaculum</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2006</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2006 Jan</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">188</style></volume><pages><style face="normal" font="default" size="100%">525-31</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;The hyperthermophilic archaeon Pyrobaculum aerophilum used 20 mM Fe(III) citrate, 100 mM poorly crystalline Fe(III) oxide, and 10 mM KNO3 as terminal electron acceptors. The two forms of iron were reduced at different rates but with equal growth yields. The insoluble iron was reduced when segregated spatially by dialysis tubing, indicating that direct contact with the iron was not necessary for growth. When partitioned, there was no detectable Fe(III) or Fe(II) outside of the tubing after growth, suggesting that an electron shuttle, not a chelator, may be used as an extracellular mediator of iron reduction. The addition of 25 and 50% (vol vol(-1)) cell-free spent insoluble iron media to fresh media led to growth without a lag phase. Liquid chromatography analysis of spent media showed that cultures grown in iron, especially insoluble iron, produced soluble extracellular compounds that were absent or less abundant in spent nitrate medium. NADH-dependent ferric reductase activity increased approximately 100-fold, while nitrate reductase activity decreased 10-fold in whole-cell extracts from iron-grown cells relative to those from nitrate-grown cells, suggesting that dissimilatory iron reduction was regulated. A novel 2,6-anthrahydroquinone disulfonate oxidase activity was more than 580-fold higher in iron-grown cells than in nitrate-grown cells. The activity was primarily (&gt;95%) associated with the membrane cellular fraction, but its physiological function is unknown. Nitrate-grown cultures produced two membrane-bound, c-type cytochromes that are predicted to be monoheme and part of nitrite reductase and a bc1 complex using genome analyses. Only one cytochrome was present in cells grown on Fe(III) citrate whose relative abundance was unchanged.&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">2</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/16385043?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%">Hu, Yajing</style></author><author><style face="normal" font="default" size="100%">Holden, James F</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Citric acid cycle in the hyperthermophilic archaeon Pyrobaculum islandicum grown autotrophically, heterotrophically, and mixotrophically with acetate.</style></title><secondary-title><style face="normal" font="default" size="100%">J Bacteriol</style></secondary-title><alt-title><style face="normal" font="default" size="100%">J. Bacteriol.</style></alt-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Acetates</style></keyword><keyword><style  face="normal" font="default" size="100%">Carbon Dioxide</style></keyword><keyword><style  face="normal" font="default" size="100%">Citric Acid</style></keyword><keyword><style  face="normal" font="default" size="100%">Citric Acid Cycle</style></keyword><keyword><style  face="normal" font="default" size="100%">Culture Media</style></keyword><keyword><style  face="normal" font="default" size="100%">Deuterium</style></keyword><keyword><style  face="normal" font="default" size="100%">Ligases</style></keyword><keyword><style  face="normal" font="default" size="100%">Lyases</style></keyword><keyword><style  face="normal" font="default" size="100%">Pyrobaculum</style></keyword><keyword><style  face="normal" font="default" size="100%">Pyruvate Synthase</style></keyword><keyword><style  face="normal" font="default" size="100%">Substrate Specificity</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2006</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2006 Jun</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">188</style></volume><pages><style face="normal" font="default" size="100%">4350-5</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;The hyperthermophilic archaeon Pyrobaculum islandicum uses the citric acid cycle in the oxidative and reductive directions for heterotrophic and autotrophic growth, respectively, but the control of carbon flow is poorly understood. P. islandicum was grown at 95 degrees C autotrophically, heterotrophically, and mixotrophically with acetate, H2, and small amounts of yeast extract and with thiosulfate as the terminal electron acceptor. The autotrophic growth rates and maximum concentrations of cells were significantly lower than those in other media. The growth rates on H2 and 0.001% yeast extract with and without 0.05% acetate were the same, but the maximum concentration of cells was fourfold higher with acetate. There was no growth with acetate if 0.001% yeast extract was not present, and addition of H2 to acetate-containing medium greatly increased the growth rates and maximum concentrations of cells. P. islandicum cultures assimilated 14C-labeled acetate in the presence of H2 and yeast extract with an efficiency of 55%. The activities of 11 of 19 enzymes involved in the central metabolism of P. islandicum were regulated under the three different growth conditions. Pyruvate synthase and acetate:coenzyme A (CoA) ligase (ADP-forming) activities were detected only in heterotrophically grown cultures. Citrate synthase activity decreased in autotrophic and acetate-containing cultures compared to the activity in heterotrophic cultures. Acetylated citrate lyase, acetate:CoA ligase (AMP forming), and phosphoenolpyruvate carboxylase activities increased in autotrophic and acetate-containing cultures. Citrate lyase activity was higher than ATP citrate synthase activity in autotrophic cultures. These data suggest that citrate lyase and AMP-forming acetate:CoA ligase, but not ATP citrate synthase, work opposite citrate synthase to control the direction of carbon flow in the citric acid cycle.&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">12</style></issue><custom1><style face="normal" font="default" size="100%">http://www.ncbi.nlm.nih.gov/pubmed/16740941?dopt=Abstract</style></custom1></record></records></xml>