skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Terminal Electron Acceptors Influence the Quantity and Chemical Composition of Capsular Exopolymers Produced by Anaerobically Growing Shewanella spp.

Abstract

No abstract prepared.

Authors:
Publication Date:
Research Org.:
Savannah River Ecology Laboratory (SREL), Aiken, SC
Sponsoring Org.:
USDOE
OSTI Identifier:
898791
Report Number(s):
SREL-2998
TRN: US200706%%255
DOE Contract Number:
DE-FC09-07SR22506
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biomacromolecules; Journal Volume: 8
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; ANAEROBIC CONDITIONS; MICROORGANISMS; EXOSKELETON; POLYMERS; BIOSYNTHESIS; CHEMICAL COMPOSITION; ELECTRON TRANSFER; VALENCE

Citation Formats

Neal, A. L., S. N. Dublin, J. Taylor, D. J. Bates, J. L. Burns, R. P. Apkarian and T. J. DiChristina. Terminal Electron Acceptors Influence the Quantity and Chemical Composition of Capsular Exopolymers Produced by Anaerobically Growing Shewanella spp.. United States: N. p., 2007. Web. doi:10.1021/bm060826e.
Neal, A. L., S. N. Dublin, J. Taylor, D. J. Bates, J. L. Burns, R. P. Apkarian and T. J. DiChristina. Terminal Electron Acceptors Influence the Quantity and Chemical Composition of Capsular Exopolymers Produced by Anaerobically Growing Shewanella spp.. United States. doi:10.1021/bm060826e.
Neal, A. L., S. N. Dublin, J. Taylor, D. J. Bates, J. L. Burns, R. P. Apkarian and T. J. DiChristina. Mon . "Terminal Electron Acceptors Influence the Quantity and Chemical Composition of Capsular Exopolymers Produced by Anaerobically Growing Shewanella spp.". United States. doi:10.1021/bm060826e.
@article{osti_898791,
title = {Terminal Electron Acceptors Influence the Quantity and Chemical Composition of Capsular Exopolymers Produced by Anaerobically Growing Shewanella spp.},
author = {Neal, A. L., S. N. Dublin, J. Taylor, D. J. Bates, J. L. Burns, R. P. Apkarian and T. J. DiChristina},
abstractNote = {No abstract prepared.},
doi = {10.1021/bm060826e},
journal = {Biomacromolecules},
number = ,
volume = 8,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • To gain insight into the complex structure of the energy-generating networks in the dissimilatory metal reducer Shewanella oneidensis MR-1, global mRNA patterns were examined in cells exposed to a wide range of metal and non-metal electron acceptors. Gene expression patterns were similar irrespective of which metal ion was used as electron acceptor, with 60% of the differentially expressed genes showing similar induction or repression relative to fumarate- respiring conditions. Several groups of genes exhibited elevated expression levels in the presence of metals, including those encoding putative multidrug efflux transporters, detoxification proteins, extracytoplasmic sigma factors and PAS-domain regulators. Only one ofmore » the 42 predicted c-type cytochromes in MR-1, SO3300, displayed significantly elevated transcript levels across all metal-reducing conditions. Genes encoding decaheme cytochromes MtrC and MtrA that were previously linked to the reduction of different forms of Fe(III) and Mn(IV), exhibited only slight decreases in relative mRNA abundances under metal-reducing conditions. In contrast, specific transcriptome responses were displayed to individual non-metal electron acceptors resulting in the identification of unique groups of nitrate-, thiosulfate- and TMAO-induced genes including previously uncharacterized multi-cytochrome gene clusters. Collectively, the gene expression results reflect the fundamental differences between metal and non-metal respiratory pathways of S. oneidensis MR-1, where the coordinate induction of detoxification and stress response genes play a key role in adaptation of this organism under metal-reducing conditions. Moreover, the relative paucity and/or the constitutive nature of genes involved in electron transfer to metals is likely due to the low-specificity and the opportunistic nature of the metal-reducing electron transport pathways.« less
  • Abstract MtrC is a decaheme c-type cytochrome associated with the outer cell membrane of Fe(III)-respiring species of the Shewanella genus. It is proposed to play a role in anaerobic respiration by mediating electron transfer to extracellular mineral oxides that can serve as terminal electron acceptors. The present work presents the first spectropotentiometric and voltammetric characterization of MtrC, using protein purified from Shewanella oneidensis MR-1. Potentiometric titrations, monitored by UV–vis absorption and electron paramagnetic resonance (EPR) spectroscopy, reveal that the hemes within MtrC titrate over a broad potential range spanning between approximately +100 and approximately *500 mV (vs. the standard hydrogenmore » electrode). Across this potential window the UV– vis absorption spectra are characteristic of low-spin c-type hemes and the EPR spectra reveal broad, complex features that suggest the presence of magnetically spin-coupled lowspin c-hemes. Non-catalytic protein film voltammetry of MtrC demonstrates reversible electrochemistry over a potential window similar to that disclosed spectroscopically. The voltammetry also allows definition of kinetic properties of MtrC in direct electron exchange with a solid electrode surface and during reduction of a model Fe(III) substrate. Taken together, the data provide quantitative information on the potential domain in which MtrC can operate.« less
  • Changes in mRNA and protein expression profiles of Shewanella oneidenesis MR-1 during switch from aerobic to fumarate-, Fe(III)-, or nitrate-reducing conditions were examined using DNA microarrays and two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). In response to changes in growth conditions, 121 of the 691 arrayed genes displayed at least a two-fold difference in transcript abundance as determined by microarray analysis. Genes involved in aerobic respiration encoding cytochrome c and d oxidases and TCA cycle enzymes were repressed under anaerobic conditions. Genes induced during anaerobic respiration included those involved in cofactor biosynthesis and assembly (moaACE, ccmHF, nosD, cysG), substrate transport (cysUP,more » cysTWA, dcuB), and anaerobic energy metabolism (dmsAB, psrC, pshA, hyaABC, hydA). Transcription of genes encoding a periplasmic nitrate reductase (napBHGA), cytochrome c{sub 552}, and prismane was elevated 8- to 56-fold in response to the presence of nitrate, while cymA, ifcA, and frdA were specifically induced three- to eightfold under fumarate-reducing conditions. The mRNA levels for two oxidoreductase-like genes of unknown function and several cell envelope genes involved in multidrug resistance increased two- to fivefold specifically under Fe(III)-reducing conditions. Analysis of protein expression profiles under aerobic and anaerobic conditions revealed 14 protein spots that showed significant differences in abundance on 2-D gels. Protein identification by mass spectrometry indicated that the expression of prismane, dihydrolipoamide succinyltransferase, and alcaligin siderophore biosynthesis protein correlated with the microarray data.« less
  • The genomes of Shewanella oneidensis strain MR-1 and Anaeromyxobacter dehalogenans strain 2CP-C encode 40 and 69 putative c-type cytochrome genes, respectively. Deletion mutant and biochemical studies have assigned specific functions to a few c-type cytochromes involved in electron transfer to oxidised metals in Shewanella oneidensis strain MR-1. Although promising, the genetic approach is limited to gene deletions that produce a distinct phenotype, and organism for which a genetic system is available. To more comprehensively investigate and compare c-type cytochrome expression in Shewanella oneidensis strain MR-1 and Anaeromyxobacter dehalogenans strain 2CP-C, proteomic measurements were used to characterise lysates of cells grownmore » with soluble Fe(III) (as ferric citrate) and insoluble Mn(IV) (as MnO2) as electron acceptors. Strain MR-1 expressed 19 and 20, and strain 2CP-C expressed 27 and 25 c-type cytochromes when grown with Fe(III) and Mn(IV), respectively. The majority of c-type cytochromes (77% for strain MR-1 and 63% for strain 2CP-C) were expressed under both growth conditions; however, the analysis also revealed unique c-type cytochromes that were specifically expressed in cells grown with soluble Fe(III) or insoluble Mn(IV). Proteomic characterisation proved to be a promising approach for determining the c-type cytochrome complement expressed under different growth conditions, and will help elucidating the specific functions of more c-type cytochromes that are the basis for Shewanella and Anaeromyxobacter respiratory versatility.« less