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At least 19 recordsLinked to original sources
PubMed2002

Effects of Fe(III) chemical speciation on dissimilatory Fe(III) reduction by Shewanella putrefaciens.

Shewanella putrefaciens, a heterotrophic member of the gamma-proteobacteria is capable of respiring anaerobically on Fe(III) as the sole terminal electron acceptor (TEA). Recent genetic and biochemical studies have indicated that anaerobic Fe(III) respiration by S. putrefaciens requires outer-membrane targeted secretion of respiration-linked Fe(III) reductases. Thus, the availability of Fe(III) to S. putrefaciens may be governed by equilibrium chemical speciation both in the solution phase and at the bacterial cell-aqueous or cell-mineral interface. In the present study, effects of Fe(III) speciation on rates of bacterial Fe(III) reduction have been systematically examined by cultivating S. putrefaciens anaerobically on a suite of Fe(III)-organic complexes as the sole TEA. The suite of Fe(III)-organic complexes spans the range of stability constants normally encountered in natural water systems and includes Fe(III) complexed to citrate, 5-sulfosalicylate, NTA, salicylate, tiron, and EDTA. Rates of bacterial Fe(III) reduction in the presence of dissolved chelating agents correlate with the thermodynamic stability constants of the Fe(III)-organic complexes, implying that chemical speciation governs Fe(III) bioavailability. Equilibrium Fe(III) sorption experiments measured the reversible coordination of Fe(III) with S. putrefaciens as a function of cell/Fe(III) concentration, time, and activity of competing chelating agents. Results show that S. putrefaciens readily sorbs dissolved Fe(III) but that adsorption is restricted by the presence of strong Fe(III)-chelating agents. Our results indicate that dissimilatory Fe(III) reduction by S. putrefaciens is controlled by equilibrium competition for Fe(III) between dissolved organic ligands and strongly sorbing functional groups on the cell surface.

Biological Availability↗
PubMed1990

Influence of respiratory substrate on the cytochrome content of Shewanella putrefaciens.

Shewanella putrefaciens can use trimethylamine oxide (TMAO) as electron acceptor under anoxic conditions. The associated cytochromes induced during growth under various respiratory conditions have been separated by liquid chromatography (DEAE Sepharose CL6b) and SDS-PAGE and characterized spectrophotometrically and by redox potentiometry. Two major low potential cytochromes and at least three minor low potential cytochromes, likely to be involved in TMAO reduction, were found. No cytochrome specific for TMAO reductase was found.

Chromatography, High Pressure Liquid↗
PubMed1995

Anaerobic electron acceptor chemotaxis in Shewanella putrefaciens.

Shewanella putrefaciens MR-1 can grow either aerobically or anaerobically at the expense of many different electron acceptors and is often found in abundance at redox interfaces in nature. Such redox interfaces are often characterized by very strong gradients of electron acceptors resulting from rapid microbial metabolism. The coincidence of S. putrefaciens abundance with environmental gradients prompted an examination of the ability of MR-1 to sense and respond to electron acceptor gradients in the laboratory. In these experiments, taxis to the majority of the electron acceptors that S. putrefaciens utilizes for anaerobic growth was seen. All anaerobic electron acceptor taxis was eliminated by the presence of oxygen, nitrate, nitrite, elemental sulfur, or dimethyl sulfoxide, even though taxis to the latter was very weak and nitrate and nitrite respiration was normal in the presence of dimethyl sulfoxide. Studies with respiratory mutants of MR-1 revealed that several electron acceptors that could not be used for anaerobic growth nevertheless elicited normal anaerobic taxis. Mutant M56, which was unable to respire nitrite, showed normal taxis to nitrite, as well as the inhibition of taxis to other electron acceptors by nitrite. These results indicate that electron acceptor taxis in S. putrefaciens does not conform to the paradigm established for Escherichia coli and several other bacteria. Carbon chemo-taxis was also unusual in this organism: of all carbon compounds tested, the only positive response observed was to formate under anaerobic conditions.

Bacteria, Anaerobic↗
PubMed1996

Purification and properties of a low-redox-potential tetraheme cytochrome c3 from Shewanella putrefaciens.

Shewanella putrefaciens is a facultatively anaerobic bacterium in the gamma group of the proteobacteria, capable of utilizing a wide variety of anaerobic electron acceptors. An examination of its cytochrome content revealed the presence of a tetraheme, low-redox-potential (E'o = -233 mV), cytochrome c-type cytochrome with a molecular mass of 12,120 Da and a pI of 5.8. The electron spin resonance data indicate a bis-histidine coordination of heme groups. Reduction of ferric citrate was accompanied by oxidation of the cytochrome. The biochemical properties suggested that this protein was in the cytochrome c3 group, which is supported by N-terminal sequence data up to the first heme binding site.

Amino Acid Sequence↗
PubMed1997

Differentiation of Shewanella putrefaciens and Shewanella alga on the basis of whole-cell protein profiles, ribotyping, phenotypic characterization, and 16S rRNA gene sequence analysis.

Seventy-six presumed Shewanella putrefaciens isolates from fish, oil drillings, and clinical specimens, the type strain of Shewanella putrefaciens (ATCC 8071), the type strain of Shewanella alga (IAM 14159), and the type strain of Shewanella hanedai (ATCC 33224) were compared by several typing methods. Numerical analysis of sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell protein and ribotyping patterns showed that the strains were separated into two distinct clusters with 56% +/- 10% and 40% +/- 14% similarity for whole-cell protein profiling and ribotyping, respectively. One cluster consisted of 26 isolates with 52 to 55 mol% G + C and included 15 human isolates, mostly clinical specimens, 8 isolates from marine waters, and the type strain of S. alga. This homogeneous cluster of mesophilic, halotolerant strains was by all analyses identical to the recently defined species S. alga (U. Simidu et al., Int. J. Syst. Bacteriol, 40:331-336, 1990). Fifty-two typically psychrotolerant strains formed the other, more heterogeneous major cluster, with 43 to 47 mol% G + C. The type strain of S. putrefaciens was included in this group. The two groups were confirmed by 16S rRNA gene sequence analysis. It is concluded that the isolates must be considered two different species, S. alga and S. putrefaciens, and that most mesophilic isolates formerly identified as S. putrefaciens belong to S. alga. The ecological role and potential pathogenicity of S. alga can be evaluated only if the organism is correctly identified.

Animals↗
PubMed1997

Skin and soft-tissue manifestations of Shewanella putrefaciens infection.

Shewanella putrefaciens, a saprophytic gram-negative rod, is infrequently recovered from clinical specimens. Although a number of clinical syndromes have been attributed to S. putrefaciens, the pathogenic role of this agent remains largely undefined. We report 16 cases of S. putrefaciens infection that occurred at the Veterans General Hospital-Kaohsiung in Taiwan between 1990 and 1995. S. putrefaciens infection was associated with a wide clinical spectrum including bacteremia/septicemia, skin and soft-tissue infection, biliary tract infection, peritonitis, and empyema. Five of our patients had skin and soft-tissue manifestations, including fulminant periorbitofacial cellulitis, dacryocystitis, perineal abscess, finger abscess, and postcholecystectomy wound infection. These clinical features deviated from the chronic ulcers or infected burns of the lower extremities that have been described in previous reports. Seven (44%) of our 16 patients had bacteremia/septicemia, and all seven had underlying hepatobiliary diseases. S. putrefaciens was isolated in mixed cultures of specimens from 14 patients; Escherichia coli was the most common coisolate. Hepatobiliary diseases and malignancy were the major predisposing factors for S. putrefaciens infection of the biliary tract and S. putrefaciens bacteremia/septicemia.

Aged↗
PubMed1993

Involvement of cytochromes in the anaerobic biotransformation of tetrachloromethane by Shewanella putrefaciens 200.

Shewanella putrefaciens 200 is an obligate respiratory bacterium that can utilize a variety of terminal electron acceptors, e.g., NO3-, NO2-, Fe(III), and trimethylamine N-oxide, in the absence of O2. The bacterium catalyzed the reductive transformation of tetrachloromethane (CT) under anaerobic conditions. The only identified product was trichloromethane (CF), but CF production was not stoichiometric. No dichloromethane, chloromethane, or methane was produced. A chloride mass balance indicated that fully dechlorinated products were not formed. Studies with [14C]CT suggested that a portion of the transformed CT reacted with biomass to form unidentified soluble and insoluble products. Intermediate production of a trichloromethyl radical can explain observed product distribution without significant CO2 formation. Evidence suggests that respiratory c-type cytochromes are responsible for the dehalogenation ability of S. putrefaciens 200. Previous growth under microaerobic conditions ([O2], < 2.5 microM) results in (i) a 2.6-fold increase in specific heme c content and (ii) a 2.3-fold increase in specific rates of anaerobic CT transformation. Manipulation of heme content by growth on iron-free medium or medium amended with delta-aminolevulinic acid showed that CT transformation rates increase with increases in specific heme c content. Transformation of CT is inhibited by CO. Dehalogenation studies with periplasmic, cytoplasmic, and membrane fractions indicated that only periplasmic and membrane fractions possessed dehalogenation ability. Cytochromes c were the predominant cytochromes present. Membranes were also found to contain smaller amounts of cytochrome b. Observed CT transformation patterns are consistent with a cometabolic description involving fortuitous CT reduction by reduced c-type cytochromes.

Biotransformation↗
PubMed1995

Effects of electron donor and acceptor conditions on reductive dehalogenation of tetrachloromethane by Shewanella putrefaciens 200.

Shewanella putrefaciens 200 is a nonfermentative bacterium that is capable of dehalogenating tetrachloromethane to chloroform and other, unidentified products under anaerobic conditions. Since S. putrefaciens 200 can respire anaerobically by using a variety of terminal electron acceptors, including NO3-, NO2-, and Fe(III), it provides a unique opportunity to study the competitive effects of different electron acceptors on dehalogenation in a single organism. The results of batch studies showed that dehalogenation of CT by S. putrefaciens 200 was inhibited by O2, 10 mM NO3-, and 3 mM NO2-, but not by 15 mM Fe(III), 15 mM fumarate, or 15 mM trimethylamine oxide. Using measured O2, Fe(III), NO2-, and NO3- reduction rates, we developed a speculative model of electron transport to explain inhibition patterns on the basis of (i) the kinetics of electron transfer at branch points in the electron transport chain, and (ii) possible direct inhibition by nitrogen oxides. In additional experiments in which we used 20 mM lactate, 20 mM glucose, 20 mM glycerol, 20 mM pyruvate, or 20 mM formate as the electron donor, dehalogenation rates were independent of the electron donor used. The results of other experiments suggested that sufficient quantities of endogenous substrates were present to support transformation of tetrachloromethane even in the absence of an exogenous electron donor. Our results should be significant for evaluating (i) the bioremediation potential at sites contaminated with both halogenated organic compounds and nitrogen oxides, and (ii) the bioremediation potential of iron-reducing bacteria at contaminated locations containing significant amounts of iron-bearing minerals.

Carbon Tetrachloride↗
PubMed1999

Phylogeny of marine and freshwater Shewanella: reclassification of Shewanella putrefaciens NCIMB 400 as Shewanella frigidimarina.

Dissimilatory Fe(III) reduction by Shewanella putrefaciens and related species has generated considerable interest in biochemical characterization of the pathways for anaerobic electron transfer in this organism. Two strains, MR-1 and NCIMB 400, have been extensively used, and several respiratory enzymes have been isolated from each. It has become apparent that significant sequence differences exist between homologous proteins from these strains. The 16S rRNA from NCIMB 400 was sequenced and compared to the sequences from MR-1 and other Shewanella strains. The results indicate that NCIMB 400 is significantly more closely related to the newly identified Shewanella frigidimarina than to the S. putrefaciens type strain. It is therefore proposed that NCIMB 400 should be reclassified as S. frigidimarina.

Base Sequence↗
PubMed2000

Chromium(VI) reductase activity is associated with the cytoplasmic membrane of anaerobically grown Shewanella putrefaciens MR-1.

Shewanella putrefaciens MR-1 can reduce a diverse array of compounds under anaerobic conditions, including manganese and iron oxides, fumarate, nitrate, and many other compounds. These reductive processes are apparently linked to a complex electron transport system. Chromium (Cr) is a toxic and mutagenic metal and bacteria could potentially be utilized to immobilize Cr by reducing the soluble and bioavailable state, Cr(VI), to the insoluble and less bioavailable state, Cr(III). Formate-dependent Cr(VI) reductase activity was detected in anaerobically grown cells of S. putrefaciens MR-1, with highest specific activity in the cytoplasmic membrane. Both formate and NADH served as electron donors for Cr(VI) reductase, whereas L-lactate or NADPH did not support any activity. The addition of 10 micromol l(-1) FMN markedly stimulated formate-dependent Cr(VI) reductase, and the activity was almost completely inhibited by diphenyliodonium chloride, an inhibitor of flavoproteins. Cr(VI) reductase activity was also inhibited by p-chloromercuriphenylsulphonate, azide, 2-heptyl-4-hydroxyquinolone-N-oxide, and antimycin A, suggesting involvement of a multi-component electron transport chain which could include cytochromes and quinones. Cr(V) was detected by electron paramagnetic resonance (EPR) spectroscopy, suggesting a one-electron reduction as the first step.

Anaerobiosis↗
PubMed2001

MtrC, an outer membrane decahaem c cytochrome required for metal reduction in Shewanella putrefaciens MR-1.

Shewanella putrefaciens is a facultative anaerobe that can use metal oxides as terminal electron acceptors during anaerobic respiration. Two proteins, MtrB and Cct, have been identified that are specifically involved in metal reduction. Analysis of S. putrefaciens mutants deficient in metal reduction led to the identification of two additional proteins that are involved in this process. MtrA is a periplasmic decahaem c-type cytochrome that appears to be part of the electron transport chain, which leads to Fe(III) and Mn(IV) reduction. MtrC is an outer membrane decahaem c-type cytochrome that appears to be required for the activity of the terminal Fe(III) reductase. Membrane fractions of mutants deficient in MtrC exhibited a decreased level of Fe(III) reduction compared with the wild type. We suggest that MtrC may be a component of the terminal reductase or may be required for its assembly.

Anaerobiosis↗
PubMed1998

Physiological function and regulation of flavocytochrome c3, the soluble fumarate reductase from Shewanella putrefaciens NCIMB 400.

Shewanella putrefaciens produces a soluble flavocytochrome c under anaerobic growth conditions. This protein shares sequence similarity with the catalytic subunits of membrane-bound fumarate reductases from Escherichia coli and other bacteria and the purified protein has fumarate reductase activity. It is shown here that this enzyme, flavocytochrome c3, is essential for fumarate respiration in vivo since disruption of the chromosomal fccA gene, which encodes flavocytochrome c3, leads to a specific loss of the ability to grow with fumarate as terminal electron acceptor. Growth with nitrate, trimethylamine N-oxide (TMAO) and other acceptors was unaffected. The fccA gene is transcribed as a 2 kb monocistronic mRNA. An adjacent reading frame that bears limited sequence similarity to one of the membrane anchor subunits of E. coli fumarate reductase is not co-transcribed with fccA. Expression of the fccA gene is regulated by anaerobiosis and by the availability of alternative electron acceptors, particularly nitrate and TMAO. DNA sequences have been identified that are required for this regulation.

Animals↗
PubMed1998

Reclassification of Shewanella putrefaciens Owen's genomic group II as Shewanella baltica sp. nov.

The taxonomic relationship between several Shewanella putrefaciens isolates from the Baltic Sea and reference strains of this species is presented in this study. Results from DNA-DNA hybridization using a newly developed non-radioactive detection system and from 16S rRNA gene sequencing demonstrated that S. putrefaciens is a heterogeneous species containing more than a single genomic group. The genomic group II was phylogenetically, genotypically and phenotypically distant enough from the species type strain to be classified as a single species within the genus Shewanella. Therefore, we propose to reclassify Owen's genomic group II as Shewanella baltica sp. nov. with the type strain NCTC 10735.

DNA, Bacterial↗
PubMed2002

Impact of electrode composition on electricity generation in a single-compartment fuel cell using Shewanella putrefaciens.

The production of electricity by Shewanella putrefaciens in the absence of exogenous electron acceptors was examined in a single compartment fuel cell with different types of electrodes and varying physiological conditions. Electricity production was dependent on anode composition, electron donor type and cell concentration. A maximum current of 2.5 mA and a current density of 10.2 mW/m(2)electrode was obtained with a Mn(4+) graphite anode, 200 mM sodium lactate and a cell concentration of 3.9 g cell protein/ml. Current production by S. putrefaciens was enhanced 10-fold when an electron mediator (i.e., Mn(4+) or neutral red) was incorporated into the graphite anode.

Electricity↗
PubMed1997

Biosynthesis of furan fatty acids (F-acids) by a marine bacterium, Shewanella putrefaciens.

A mutant derived from Shewanella putrefaciens 8CS7-4 treated with N-methyl-N'-nitro-N-nitrosoguanidine was found to produce 15-20 mg of a furan fatty acid (F-acid), 10,13-epoxy-11-methyloctadeca-10,12-dienoic acid (F18), per liter of growth medium (10-15% of total fatty acids). Capillary gas chromatography-mass spectrometry and proton nuclear magnetic resonance analysis of the fatty acid methyl esters of the mutant revealed the presence of other F-acids, 8,11-epoxy-9-methylhexadeca-8,10-dienoic acid (F16), 6,9-epoxy-7-methyltetradeca-6,8-dienoic acid (F14), and methyl branched unsaturated fatty acids, 11-methyl-12E-octadecenoic acid (11-me-18:1) and 11-methyl-10E,12E-octadecadienoic acid (1-me-18:2). About 90% of F-acids were present in phospholipids, in which the F-acids were found to be exclusively linked at the sn-1 position. 11-me-18:1 and 11-me-18:2 were also detected in the sn-1 position. Firstly, 11-me-18:1 increased and reached a maximum at 12 h, and then decreased rapidly. Secondly, the 11-me-18:2 content reached a maximum at 24 h, when 11-me-18:1 was little detected, and then decreased. Finally, the amount of F18 began to increase after 20 h and reached a plateau at 36 h. These results suggest that 11-me-18:1 and 11-me-18:2 are precursors of F18.

Animals↗
PubMed2002

Role of menaquinones in Fe(III) reduction by membrane fractions of Shewanella putrefaciens.

Two Tn5-generated mutants of Shewanella putrefaciens with insertions in menD and menB were isolated and analyzed. Both mutants were deficient in the use of several terminal electron acceptors, including Fe(III). This deficiency was overcome by the addition of menaquinone (vitamin K(2)). Isolated membrane fractions from both mutants were unable to reduce Fe(III) in the absence of added menaquinone when formate was used as the electron donor. These results indicate that menaquinones are essential components for the reduction of Fe(III) by both whole cells and purified membrane fractions when formate or lactate is used as the electron donor.

Alkyl and Aryl Transferases↗
PubMedDate not supplied

In vitro study of TMAO reduction by Shewanella putrefaciens isolated from cod fillets packed in modified atmosphere.

A strain of Shewanella putrefaciens was isolated from cod fillets in a modified atmosphere (60% CO2, 30% O2, 10% N2). The effect of pH on the growth of Shewanella putrefaciens and TMAO reduction was studied in fish extract with citrate buffer systems at pH values from 5.8 to 6.8. The effect of the modified atmosphere (CO2, O2) on the growth of S. putrefaciens and on the reduction of TMAO to TMA was studied using solid media from fish extract packed under variable mixtures of CO2, O2 and N2. All the samples were incubated at 7 degrees C for 7 days. Slow development of S. putrefaciens and no production of TMA was observed in fish extract buffered at pH 5.8. Inclusion of O2 in packaging atmosphere of solid fish extract, even at small proportions (10%), was inhibitory for the reduction of TMAO, while there was no effect of O2 on the growth of S. putrefaciens. Increased levels of CO2 (> or = 50%) in the atmosphere were inhibiting the growth of S. putrefaciens and consequently the production of TMA.

Animals↗