Journal article
Extracellular Reduction of Hexavalent Chromium by Cytochromes MtrC and OmcA of Shewanella oneidensis MR-1
Applied and environmental microbiology, Vol.77(12), pp.4035-4041
06/2011
Handle:
https://hdl.handle.net/2376/102088
PMCID: PMC3131624
PMID: 21498755
Abstract
To characterize the roles of cytochromes MtrC and OmcA of
Shewanella oneidensis
MR-1 in Cr(VI) reduction, the effects of deleting the
mtrC
and/or
omcA
gene on Cr(VI) reduction and the cellular locations of reduced Cr(III) precipitates were investigated. Compared to the rate of reduction of Cr(VI) by the wild type (wt), the deletion of
mtrC
decreased the initial rate of Cr(VI) reduction by 43.5%, while the deletion of
omcA
or both
mtrC
and
omcA
lowered the rate by 53.4% and 68.9%, respectively. In wt cells, Cr(III) precipitates were detected by transmission electron microscopy in the extracellular matrix between the cells, in association with the outer membrane, and inside the cytoplasm. No extracellular matrix-associated Cr(III) precipitates, however, were found in the cytochrome mutant cell suspension. In mutant cells without either MtrC or OmcA, most Cr(III) precipitates were found in association with the outer membrane, while in mutant cells lacking both MtrC and OmcA, most Cr(III) precipitates were found inside the cytoplasm. Cr(III) precipitates were also detected by scanning election microscopy on the surfaces of the wt and mutants without MtrC or OmcA but not on the mutant cells lacking both MtrC and OmcA, demonstrating that the deletion of
mtrC
and
omcA
diminishes the extracellular formation of Cr(III) precipitates. Furthermore, purified MtrC and OmcA reduced Cr(VI) with apparent
k
cat
values of 1.2 ± 0.2 (mean ± standard deviation) and 10.2 ± 1 s
−1
and
K
m
values of 34.1 ± 4.5 and 41.3 ± 7.9 μM, respectively. Together, these results consistently demonstrate that MtrC and OmcA are the terminal reductases used by
S. oneidensis
MR-1 for extracellular Cr(VI) reduction where OmcA is a predominant Cr(VI) reductase.
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Details
- Title
- Extracellular Reduction of Hexavalent Chromium by Cytochromes MtrC and OmcA of Shewanella oneidensis MR-1
- Creators
- Sara M Belchik - Pacific Northwest National Laboratory, Richland, Washington 99352David W Kennedy - Pacific Northwest National Laboratory, Richland, Washington 99352Alice C Dohnalkova - Pacific Northwest National Laboratory, Richland, Washington 99352Yuanmin Wang - Bowling Green State University, Department of Chemistry, Center for Photochemical Sciences, Bowling Green, Ohio 43403Papatya C Sevinc - Bowling Green State University, Department of Chemistry, Center for Photochemical Sciences, Bowling Green, Ohio 43403Hong Wu - Pacific Northwest National Laboratory, Richland, Washington 99352Yuehe Lin - Pacific Northwest National Laboratory, Richland, Washington 99352H. Peter Lu - Bowling Green State University, Department of Chemistry, Center for Photochemical Sciences, Bowling Green, Ohio 43403James K Fredrickson - Pacific Northwest National Laboratory, Richland, Washington 99352Liang Shi - Pacific Northwest National Laboratory, Richland, Washington 99352
- Publication Details
- Applied and environmental microbiology, Vol.77(12), pp.4035-4041
- Academic Unit
- Mechanical and Materials Engineering, School of
- Publisher
- American Society for Microbiology; 1752 N St., N.W., Washington, DC
- Identifiers
- 99900546536801842
- Language
- English
- Resource Type
- Journal article