TY - JOUR
T1 - Changes in the structure of birnessite during siderophore-promoted dissolution
T2 - A time-resolved synchrotron X-ray diffraction study
AU - Fischer, Timothy B.
AU - Heaney, Peter J.
AU - Post, Jeffrey E.
N1 - Funding Information:
Funding for this research was provided by NSF grants EAR-1552211 and EAR07-45374 , the Center for Environmental Kinetics Analysis (CEKA), an NSF- and DOE-sponsored Environmental Molecular Science Institute (NSF CHE04-31328 ), the Edward H. Kraus Crystallographic Research Fund of the Mineralogical Society of America , and by a Geological Society of America Graduate Student Research Grant. This research was carried out at the Advanced Photon Source at Argonne National Laboratory, which is supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. We thank Joanne Stubbs and Peter Eng for their assistance at beamline 13-BM-C at APS, and we are grateful to James Kubicki for sharing his calculated model of DFOB. We also thank two anonymous reviewers for their insightful comments.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2018/1/5
Y1 - 2018/1/5
N2 - We used time-resolved synchrotron X-ray diffraction to follow the complete dissolution of synthetic triclinic Na-birnessite as promoted by the trihydroxamate siderophore desferrioxamine B (DFOB). Many microorganisms employ siderophores to increase the availability of Fe, Mn, and other trace metals for metabolic processes. Our primary goal was to quantify the DFOB-assisted dissolution rate by direct, continuous observation of the solid phase. Our kinetic model indicates that the rate of dissolution is dependent on [DFOB] but not pH, and has a reaction order of 0.505 with a rate constant of 0.112 wt%birn min− 1. The unit-cell dimensions of birnessite remained virtually constant within error throughout the dissolution process, showing only a 0.3% contraction along the c-axis. Despite the small changes in unit-cell volume, Rietveld analysis revealed that the occupancy of Mn within the octahedral sheets decreased from 100% to ~ 80%, presumably as the result of complexation of structural Mn3 + with DFOB followed by extraction of Mn3 + from the crystal structure. These observations suggest a critical lacunarity of ~ 20 mol% Mn for triclinic Na-birnessite, below which the structure is destabilized. Moreover, this study reveals that DFOB-promoted dissolution must operate by a different mechanism from that engaged when bacterial membrane fractions directly transfer electrons to birnessite crystals. We propose that crystal structure analysis of minerals undergoing dissimilatory metal reduction can elucidate metabolic pathways employed by microorganisms.
AB - We used time-resolved synchrotron X-ray diffraction to follow the complete dissolution of synthetic triclinic Na-birnessite as promoted by the trihydroxamate siderophore desferrioxamine B (DFOB). Many microorganisms employ siderophores to increase the availability of Fe, Mn, and other trace metals for metabolic processes. Our primary goal was to quantify the DFOB-assisted dissolution rate by direct, continuous observation of the solid phase. Our kinetic model indicates that the rate of dissolution is dependent on [DFOB] but not pH, and has a reaction order of 0.505 with a rate constant of 0.112 wt%birn min− 1. The unit-cell dimensions of birnessite remained virtually constant within error throughout the dissolution process, showing only a 0.3% contraction along the c-axis. Despite the small changes in unit-cell volume, Rietveld analysis revealed that the occupancy of Mn within the octahedral sheets decreased from 100% to ~ 80%, presumably as the result of complexation of structural Mn3 + with DFOB followed by extraction of Mn3 + from the crystal structure. These observations suggest a critical lacunarity of ~ 20 mol% Mn for triclinic Na-birnessite, below which the structure is destabilized. Moreover, this study reveals that DFOB-promoted dissolution must operate by a different mechanism from that engaged when bacterial membrane fractions directly transfer electrons to birnessite crystals. We propose that crystal structure analysis of minerals undergoing dissimilatory metal reduction can elucidate metabolic pathways employed by microorganisms.
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U2 - 10.1016/j.chemgeo.2017.11.003
DO - 10.1016/j.chemgeo.2017.11.003
M3 - Article
AN - SCOPUS:85034805341
SN - 0009-2541
VL - 476
SP - 46
EP - 58
JO - Chemical Geology
JF - Chemical Geology
ER -