Respiration and Growth of Shewanella oneidensis MR-1 Using Vanadate as the Sole Electron Acceptor

Abstract

Shewanella oneidensis MR-1 is a free-living gram-negative ␥-proteobacterium that is able to use a large number of oxidizing molecules, including fumarate, nitrate, dimethyl sulfoxide, trimethylamine N-oxide, nitrite, and insoluble iron and manganese oxides, to drive anaerobic respiration. Here we show that S. oneidensis MR-1 is able to grow on vanadate as the sole electron acceptor. Oxidant pulse experiments demonstrated that proton translocation across the cytoplasmic membrane occurs during vanadate reduction. Proton translocation is abolished in the presence of protonophores and the inhibitors 2-heptyl-4-hydroxyquinoline N-oxide and antimycin A. Redox difference spectra indicated the involvement of membrane-bound menaquinone and cytochromes c, which was confirmed by transposon mutagenesis and screening for a vanadate reduction-deficient phenotype. Two mutants which are deficient in menaquinone synthesis were isolated. Another mutant with disruption in the cytochrome c maturation gene ccmA was unable to produce any cytochrome c and to grow on vanadate. This phenotype could be restored by complementation with the pEC86 plasmid expressing ccm genes from Escherichia coli. To our knowledge, this is the first report of E. coli ccm genes being functional in another organism. Analysis of an mtrB-deficient mutant confirmed the results of a previous paper indicating that OmcB may function as a vanadate reductase or may be part of a vanadate reductase complex.One of the primary tasks of a microorganism is to catalyze chemical reactions in order to obtain energy for metabolic growth from its environment. The most well-known electron acceptor is O 2 . However, in the absence of oxygen, some microorganisms can grow by coupling the oxidation of simple organic acids, alcohols, H 2 , or aromatic compounds to the reduction of Fe(III) or Mn(IV) (21). Fe(III) and Mn(IV) reduction has an important impact on the organic and inorganic geochemistry of anaerobic aquatic sediments and groundwater (20). Many other metals, including Fe(III), Mn(IV), Mn(III), Cr(VI), Hg(II), Au(III), Ag(I), Mo(VI), Co(III), Pd(II), As(V), Se(VI), Se(IV), U(VI), Tc(VII), Te(IV), V(V), can be enzymatically reduced, but microorganisms are not necessarily able to conserve energy from the reduction process (20,43). A distinction is made between respiratory metal reduction, in which the electron flow is coupled to a proton-translocating complex to allow ATP generation, and dissimilatory reduction, in which electrons are transferred without the generation of a proton motive force (24). Vanadate is a known electron acceptor for anaerobic respiration (9, 23, 35, 52), but only limited data are available on the biological vanadium reduction process, concomitant precipitation effects, and the geochemical implications. Although vanadium is not abundant, it is omnipresent in nature (51). Of importance is the comparatively large amount of vanadium in seawater, which contains vanadate at an average concentration of 30 nM (7). This makes vanadium the second most common tr...

Electrochemical Investigation of Isoprenoid Quinone Productions byShewanella oneidensisMR-1 Detected by Its Destructive Adsorption on an Indium-Tin-Oxide Electrode

“…The Fe(II) production was confirmed by a separate experiment, which was performed by adding K 4 [Fe(CN) 6 ] or K 3 [Fe(CN) 6 ] to the microbe-Fe(III) medium before starting the incubation (Fig. S5).…”

“…4 Shewanella oneidensis MR-1 is a facultative anaerobe that can use a variety of inorganic and organic compounds as terminal electron acceptors for anaerobic respiration, and has been often referred to as dissimilatory metal-reducing bacteria; the acceptors that have been listed include Fe(III), U(VI), Mn(IV), V(V), nitrate, dimethyl sulfoxide, and fumarate. [5][6][7] Currently, the growing interest in this species is to a large extent directed toward potential applications in biotechnology, such as remediation of soils and aquifers that have been contaminated with heavy metals or radionuclides, and a biocatalyst in microbial fuel cells. [7][8][9][10][11][12] S. oneidensis can grow not only aerobically, but also anaerobically with a variety of organic and inorganic substances as the terminal electron acceptor.…”

ISOLATION AND CHARACTERIZATION OF A MOLYBDENUM-REDUCING AND GLYPHOSATE-DEGRADING Klebsiella oxytoca STRAIN SAW-5 IN SOILS FROM SARAWAK

“…Under this conditions, other electron acceptors such as nitrate or metal ions such as manganese or iron would be used as an alternative (Haley et al, 2012). Resting cells have been used in studying heavy metals reduction such as in selenate (Losi and Jr, 1997), vanadate (Carpentier et al, 2005), chromate (Llovera et al, 1993), reductions and xenobiotics biodegradation such as phenol (Sedighi and Vahabzadeh, 2014), amides (Raj et al, 2010), diesel (Auffret et al, 2015), SDS (Chaturvedi and Kumar, 2011), and pentachlorophenol (Steiert et al, 1987).…”

Microbial reduction of chromium from the hexavalent to divalent state

“…Since Cr(III) compounds are relatively solureduction of Cr(VI) have been reported (Suzuki et al, ble only under very acidic or very basic conditions (Rai 1992;Myers et al, 2000;Neal et al, 2002;Kalabegishvili et al, 1987Kalabegishvili et al, , 1989 and their soluble organo complexes et al., 2003). Electron paramagnetic resonance (EPR) mea- (Puzon et al, 2005) are large molecules that are not easily surements, sensitive to non-integer spin transition metals transported across the outer membrane, bacteria with memsuch as Cr(I), Cr(III), and Cr(V), suggested that Cr(V) is brane-bound reductases are constrained to reduce Cr(VI) to a possible redox intermediate for Cr(VI) reduction by PseuCr(III) by extracellular processes (e.g., see Wang et al, domonas ambigua (G-1) (Suzuki et al, 1992), Arthrobacter 1990), e.g., by using electron-shuttling compounds coupled oxydans (Kalabegishvili et al, 2003), and Shewanella oneidto membrane reductases. Otherwise a mechanism of Cr(Ill) ensis (Myers et al, 2000).…”

“…1 and 2). (S032-), thiosulfate (S2032-), tetrathionate (S4062-), fumarate, glycine, and trimethylamine N-oxide (see Myers and 2.2 Nealson, 1988a,b;Lovley et al, 1991;Llyod and Macaskie, 1996;Carpentier et al, 2005).…”