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Manganese sulfide formation via concomitant microbial manganese oxide and thiosulfate reduction
Lee, Ji‐,Hoon,Kennedy, David W.,Dohnalkova, Alice,Moore, Dean A.,Nachimuthu, Ponnusamy,Reed, Samantha B.,Fredrickson, James K. Blackwell Publishing Ltd 2011 Environmental microbiology Vol.13 No.12
<P><B>Summary</B></P><P>The dissimilatory metal‐reducing bacterium, <I>Shewanella oneidensis</I> MR‐1 produced γ‐MnS (rambergite) nanoparticles during the concurrent reduction of MnO<SUB>2</SUB> and thiosulfate coupled to H<SUB>2</SUB> oxidation. To investigate effect of direct microbial reduction of MnO<SUB>2</SUB> on MnS formation, two MR‐1 mutants defective in outer membrane <I>c</I>‐type cytochromes (Δ<I>mtrC</I>/Δ<I>omcA</I> and Δ<I>mtrC</I>/Δ<I>omcA</I>/Δ<I>mtrF</I>) were also used and it was determined that direct reduction of MnO<SUB>2</SUB> was dominant relative to chemical reduction by biogenic sulfide generated from thiosulfate reduction. Although bicarbonate was excluded from the medium, incubations of strain MR‐1 with lactate as the electron donor produced MnCO<SUB>3</SUB> (rhodochrosite) as well as MnS in nearly equivalent amounts as estimated by micro X‐ray diffraction (micro‐XRD) analysis. It was concluded that carbonate released from lactate metabolism promoted MnCO<SUB>3</SUB> formation and that Mn(II) mineralogy was strongly affected by carbonate ions even in the presence of abundant sulfide and weakly alkaline conditions expected to favour the precipitation of MnS. Formation of MnS, as determined by a combination of micro‐XRD, transmission electron microscopy, energy dispersive X‐ray spectroscopy, and selected area electron diffraction analyses was consistent with equilibrium speciation modelling predictions. Biogenic manganese sulfide may be a manganese sink in the Mn biogeochemical cycle in select environments such as deep anoxic marine basins within the Baltic Sea.</P>
Gorby, Y. A.,Yanina, S.,McLean, J. S.,Rosso, K. M.,Moyles, D.,Dohnalkova, A.,Beveridge, T. J.,Chang, I. S.,Kim, B. H.,Kim, K. S.,Culley, D. E.,Reed, S. B.,Romine, M. F.,Saffarini, D. A.,Hill, E. A.,Sh Proceedings of the National Academy of Sciences 2006 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.103 No.30
<P>Shewanella oneidensis MR-1 produced electrically conductive pilus-like appendages called bacterial nanowires in direct response to electron-acceptor limitation. Mutants deficient in genes for c-type decaheme cytochromes MtrC and OmcA, and those that lacked a functional Type II secretion pathway displayed nanowires that were poorly conductive. These mutants were also deficient in their ability to reduce hydrous ferric oxide and in their ability to generate current in a microbial fuel cell. Nanowires produced by the oxygenic phototrophic cyanobacterium Synechocystis PCC6803 and the thermophilic, fermentative bacterium Pelotomaculum thermopropionicum reveal that electrically conductive appendages are not exclusive to dissimilatory metal-reducing bacteria and may, in fact, represent a common bacterial strategy for efficient electron transfer and energy distribution.</P>
Lee, D.,Lee, J.,Kim, J.,Kim, J.,Na, H. B.,Kim, B.,Shin, C.-H.,Kwak, J. H.,Dohnalkova, A.,Grate, J. W.,Hyeon, T.,Kim, H.-S. WILEY-VCH Verlag 2005 Advanced Materials Vol.17 No.23
<B>Graphic Abstract</B> <P>Glucose oxidase immobilized in mesocellular carbon foam results in a highly sensitive and fast glucose biosensor. The structure of the mesocellular foam (see Figure), with a combination of mesopores containing the glucose oxidase (GOx) enzymes and micropores and transport channels, results in high enzyme loading and low mass-transfer limitations, producing higher catalytic activity and sensitivity than polymer-matrix-based GOx glucose sensors. <img src='wiley_img/09359648-2005-17-23-ADMA200500793-content.gif' alt='wiley_img/09359648-2005-17-23-ADMA200500793-content'> </P>
Reduction of pertechnetate [Tc(VII)] by aqueous Fe(II) and the nature of solid phase redox products
Zachara, John M.,Heald, Steve M.,Jeon, Byong-Hun,Kukkadapu, Ravi K.,Liu, Chongxuan,McKinley, James P.,Dohnalkova, Alice C.,Moore, Dean A. Elsevier 2007 Geochimica et cosmochimica acta Vol.71 No.9
<P><B>Abstract</B></P><P>The subsurface behaviour of <SUP>99</SUP>Tc, a contaminant resulting from nuclear fuels reprocessing, is dependent on its valence (e.g., IV or VII). Abiotic reduction of soluble Tc(VII) by Fe(II)<SUB>(aq)</SUB> in pH 6–8 solutions was investigated under strictly anoxic conditions using an oxygen trap (<7.5×10<SUP>−9</SUP>atmO<SUB>2</SUB>). The reduction kinetics were strongly pH dependent. Complete and rapid reduction of Tc(VII) to a precipitated Fe/Tc(IV) form was observed when 11μmol/L of Tc(VII) was reacted with 0.4mmol/L Fe(II) at pH 7.0 and 8.0, while no significant reduction was observed over 1 month at pH 6.0. Experiments conducted at pH 7.0 with Fe(II)<SUB>(aq)</SUB>=0.05–0.8mmol/L further revealed that Tc(VII) reduction was a combination of homogeneous and heterogeneous reaction. Heterogeneous reduction predominated after approximately 0.01mmol/L of Fe(II) was oxidized. The heterogeneous reaction was more rapid, and was catalyzed by Fe(II) that adsorbed to the Fe/Tc(IV) redox product. Wet chemical and Fe–X-ray absorption near edge spectroscopy measurements (XANES) showed that Fe(II) and Fe(III) were present in the Fe/Tc(IV) redox products after reaction termination. <SUP>57</SUP>Fe-Mössbauer, extended X-ray adsorption fine structure (EXAFS), and transmission electron microscopy (TEM) measurements revealed that the Fe/Tc(IV) solid phase was poorly ordered and dominated by Fe(II)-containing ferrihydrite with minor magnetite. Tc(IV) exhibited homogeneous spatial distribution within the precipitates. According to Tc-EXAFS measurements and structural modeling, its molecular environment was consistent with an octahedral Tc(IV) dimer bound in bidentate edge-sharing mode to octahedral Fe(III) associated with surface or vacancy sites in ferrihydrite. The precipitate maintained Tc(IV)<SUB>aq</SUB> concentrations that were slightly below those in equilibrium with amorphous Tc(IV)O<SUB>2</SUB>·<I>n</I>H<SUB>2</SUB>O<SUB>(s)</SUB>. The oxidation rate of sorbed Tc(IV) in the Fe/Tc precipitate was considerably slower than Tc(IV)O<SUB>2</SUB>·<I>n</I>H<SUB>2</SUB>O<SUB>(s)</SUB> as a result of its intraparticle/intragrain residence. Precipitates of this nature may form in anoxic sediments or groundwaters, and the intraparticle residence of sorbed/precipitated Tc(IV) may limit <SUP>99</SUP>Tc remobilization upon the return of oxidizing conditions.</P>
Biogenic formation of photoactive arsenic-sulfide nanotubes by Shewanella sp. strain HN-41
Lee, J.-H.,Kim, M.-G.,Yoo, B.,Myung, N. V.,Maeng, J.,Lee, T.,Dohnalkova, A. C.,Fredrickson, J. K.,Sadowsky, M. J.,Hur, H.-G. Proceedings of the National Academy of Sciences 2007 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.104 No.51
<P>Microorganisms facilitate the formation of a wide range of minerals that have unique physical and chemical properties as well as morphologies that are not produced by abiotic processes. Here, we report the production of an extensive extracellular network of filamentous, arsenic-sulfide (As-S) nanotubes (20-100 nm in diameter by approximately 30 mum in length) by the dissimilatory metal-reducing bacterium Shewanella sp. HN-41. The As-S nanotubes, formed via the reduction of As(V) and S(2)O(3)(2-), were initially amorphous As(2)S(3) but evolved with increasing incubation time toward polycrystalline phases of the chalcogenide minerals realgar (AsS) and duranusite (As(4)S). Upon maturation, the As-S nanotubes behaved as metals and semiconductors in terms of their electrical and photoconductive properties, respectively. The As-S nanotubes produced by Shewanella may provide useful materials for novel nano- and opto-electronic devices.</P>
Kim, Moon Il,Kim, Jungbae,Lee, Jinwoo,Jia, Hongfei,Na, Hyon Bin,Youn, Jong Kyu,Kwak, Ja Hun,Dohnalkova, Alice,Grate, Jay W.,Wang, Ping,Hyeon, Taeghwan,Park, Hyun Gyu,Chang, Ho Nam Wiley Subscription Services, Inc., A Wiley Company 2007 Biotechnology and bioengineering Vol.96 No.2
<P>α-chymotrypsin (CT) and lipase (LP) were immobilized in hierarchically-ordered mesocellular mesoporous silica (HMMS) in a simple but effective way for the enzyme stabilization, which was achieved by the enzyme adsorption followed by glutaraldehyde (GA) crosslinking. This resulted in the formation of nanometer scale crosslinked enzyme aggregates (CLEAs) entrapped in the mesocellular pores of HMMS (37 nm), which did not leach out of HMMS through narrow mesoporous channels (13 nm). CLEA of α-chymotrypsin (CLEA-CT) in HMMS showed a high enzyme loading capacity and significantly increased enzyme stability. No activity decrease of CLEA-CT was observed for 2 weeks under even rigorously shaking condition, while adsorbed CT in HMMS and free CT showed a rapid inactivation due to the enzyme leaching and presumably autolysis, respectively. With the CLEA-CT in HMMS, however, there was no tryptic digestion observed suggesting that the CLEA-CT is not susceptible to autolysis. Moreover, CLEA of lipase (CLEA-LP) in HMMS retained 30% specific activity of free lipase with greatly enhanced stability. This work demonstrates that HMMS can be efficiently employed as host materials for enzyme immobilization leading to highly enhanced stability of the immobilized enzymes with high enzyme loading and activity. Biotechnol. Bioeng. 2007;96: 210–218. © 2006 Wiley Periodicals, Inc.</P>