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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↗
PubMed1998

Biochemical and pathogenic properties of Shewanella alga and Shewanella putrefaciens.

We characterized 49 strains of Shewanella spp. from clinical (n = 31) and nonhuman (n = 18) sources. Most Shewanella alga organisms (Gilardi biovar 2; Centers for Disease Control and Prevention [CDC] biotype 2) originated from clinical material (92%), failed to produce acid from carbohydrates other than D-ribose, and were biochemically and enzymatically fairly homogeneous. In contrast, Shewanella putrefaciens organisms (Gilardi biovars 1 and 3; CDC biotype 1) were more often associated with nonhuman sources (70%), were able to utilize a number of sugars (sucrose, L-arabinose, and maltose), and were found to exhibit wider variations in biochemical characteristics; three biotypes within S. putrefaciens were detected. Notable differences between the two species in enzymatic activity, determined with the API-ZYM system (bioMérieux, Hazelwood, Mo.), and cellular fatty acid profiles, determined by the MIDI system (Microbial ID Inc., Newark, Del.), were also detected. Pathogenicity studies of mice indicate that S. alga appears to be the more virulent species, possibly due to the production of a hemolytic substance.

Animals↗
PubMed2000

Role of the tetraheme cytochrome CymA in anaerobic electron transport in cells of Shewanella putrefaciens MR-1 with normal levels of menaquinone.

Shewanella putrefaciens MR-1 possesses a complex electron transport system which facilitates its ability to use a diverse array of compounds as terminal electron acceptors for anaerobic respiration. A previous report described a mutant strain (CMTn-1) deficient in CymA, a tetraheme cytochrome c. However, the interpretation of the electron transport role of CymA was complicated by the fact that CMTn-1 was also markedly deficient in menaquinones. This report demonstrates that the depressed menaquinone levels were the result of the rifampin resistance phenotype of the parent of CMTn-1 and not the interruption of the cymA gene. This is the first report of rifampin resistance leading to decreased menaquinone levels, indicating that rifampin-resistant strains should be used with caution when analyzing electron transport processes. A site-directed gene replacement approach was used to isolate a cymA knockout strain (MR1-CYMA) directly from MR-1. While MR1-CYMA retained menaquinone levels comparable to those of MR-1, it lost the ability to reduce iron(III), manganese(IV), and nitrate and to grow by using fumarate as an electron acceptor. All of these functions were restored to wild-type efficacy, and the presence of the cymA transcript and CymA protein was also restored, by complementation of MR1-CYMA with the cymA gene. The requirement for CymA in anaerobic electron transport to iron(III), fumarate, nitrate, and manganese(IV) is therefore not dependent on the levels of menaquinone in these cells. This represents the first successful use of a suicide vector for directed gene replacement in MR-1.

Anaerobiosis↗
PubMed2002

MtrB is required for proper incorporation of the cytochromes OmcA and OmcB into the outer membrane of Shewanella putrefaciens MR-1.

When grown under anaerobic conditions, Shewanella putrefaciens MR-1 synthesizes multiple outer membrane (OM) cytochromes, some of which have a role in the use of insoluble electron acceptors (e.g., MnO2) for anaerobic respiration. The cytochromes OmcA and OmcB are localized to the OM and the OM-like intermediate-density membrane (IM) in MR-1. The components necessary for proper localization of these cytochromes to the OM have not been identified. A gene replacement mutant (strain MTRB1) lacking the putative OM protein MtrB was isolated and characterized. The specific cytochrome content of the OM of MTRB1 was only 36% that of MR-1. This was not the result of a general decline in cytochrome content, however, because the cytoplasmic membrane (CM) and soluble fractions were not cytochrome deficient. While OmcA and OmcB were detected in the OM and IM fractions of MTRB1, significant amounts were mislocalized to the CM. OmcA was also detected in the soluble fraction of MTRB1. While OmcA and OmcB in MR-1 fractions were resistant to solubilization with Triton X-100 in the presence of Mg2+, Triton X-100 readily solubilized these proteins from all subcellular fractions of MTRB1. Together, these data suggest that MtrB is required for the proper localization and insertion of OmcA and OmcB into the OM of MR-1. The inability of MTRB1 to properly insert these, and possibly other, proteins into its OM likely contributes to its marked deficiency in manganese(IV) and iron(III) reduction. While the localization of another putative OM cytochrome (MtrF) could not be directly determined, an mtrF gene replacement mutant exhibited wild-types rates of Mn(IV) and Fe(III) reduction. Therefore, even if MtrF were mislocalized in MTRB1, it would not contribute to the loss of metal reduction activity in this strain.

Bacterial Outer Membrane Proteins↗
PubMed2001

Role for outer membrane cytochromes OmcA and OmcB of Shewanella putrefaciens MR-1 in reduction of manganese dioxide.

Shewanella putrefaciens MR-1 can use a wide variety of terminal electron acceptors for anaerobic respiration, including certain insoluble manganese and iron oxides. To examine whether the outer membrane (OM) cytochromes of MR-1 play a role in Mn(IV) and Fe(III) reduction, mutants lacking the OM cytochrome OmcA or OmcB were isolated by gene replacement. Southern blotting and PCR confirmed replacement of the omcA and omcB genes, respectively, and reverse transcription-PCR analysis demonstrated loss of the respective mRNAs, whereas mRNAs for upstream and downstream genes were retained. The omcA mutant (OMCA1) resembled MR-1 in its growth on trimethylamine N-oxide (TMAO), dimethyl sulfoxide, nitrate, fumarate, thiosulfate, and tetrathionate and its reduction of nitrate, nitrite, ferric citrate, FeOOH, and anthraquinone-2,6-disulfonic acid. Similarly, the omcB mutant (OMCB1) grew on fumarate, nitrate, TMAO, and thiosulfate and reduced ferric citrate and FeOOH. However, OMCA1 and OMCB1 were 45 and 75% slower than MR-1, respectively, at reducing MnO(2). OMCA1 lacked only OmcA. While OMCB1 lacked OmcB, other OM cytochromes were also missing or markedly depressed. The total cytochrome content of the OM of OMCB1 was less than 15% of that of MR-1. Western blots demonstrated that OMCB1 still synthesized OmcA, but most of it was localized in the cytoplasmic membrane and soluble fractions rather than in the OM. OMCB1 had therefore lost the ability to properly localize multiple OM cytochromes to the OM. Together, the results suggest that the OM cytochromes of MR-1 participate in the reduction of Mn(IV) but are not required for the reduction of Fe(III) or other electron acceptors.

Amino Acid Sequence↗
PubMed2000

Fe(III) reduction activity and cytochrome content of Shewanella putrefaciens grown on ten compounds as sole terminal electron acceptor.

Shewanella putrefaciens was grown on a series of ten alternate compounds as sole terminal electron acceptor. Each cell type was analyzed for Fe(III) reduction activity, absorbance maxima in reduced-minus-oxidized difference spectra and heme-containing protein content. High-rate Fe(III) reduction activity, pronounced difference maxima at 521 and 551 nm and a predominant 29.3 kDa heme-containing protein expressed by cells grown on Fe(III), Mn(IV), U(VI), SO3(2-) and S2O3(2-), but not by cells grown on O2, NO3, NO2-, TMAO or fumarate. These results suggest that microbial Fe(III) reduction activity is enhanced by anaerobic growth on metals and sulfur compounds, yet is limited under all other terminal electron-accepting conditions.

Cytochromes↗
PubMed2005

Shewanella algae and Shewanella putrefaciens: clinical and microbiological characteristics.

The occurrence of the two Shewanella species found in clinical specimens, Shewanella algae and Shewanella putrefaciens, correlates with the temperature and salinity of seawater. This means that Shewanella infections occur in warm climates or during especially warm summers in temperate climates. The infections described most commonly involve ears, skin and soft tissue, with or without bacteraemia. Primary bacteraemia with a fulminant course is also seen in immunocompromised patients. Important differential characteristics between the two species include the ability of S. algae to produce mucoid colonies with beta-haemolysis on sheep blood agar, to grow at 42 degrees C and in NaCl 6% w/v, and to reduce nitrite, and an inability to produce acid from maltose, all of which are in contrast to the characteristics of S. putrefaciens. Automated identification systems fail to differentiate between S. algae and S. putrefaciens, as S. algae is not included in the databases of these systems. Presumably for this reason, most Shewanella infections reported during recent years have been attributed to S. putrefaciens. However, when extensive phenotypic characterisation is performed, most human infections are seen to be caused by S. algae. As the two species seem to have different pathogenic potential for humans, correct identification is important, and this is possible in routine clinical microbiology laboratories.

Animals↗
PubMed1990

Classification of the spoilage flora of fish, with special reference to Shewanella putrefaciens.

One hundred and fifty-nine Gram-negative strains isolated from refrigerated fish, taken from the Baltic Sea or Swedish inland waters, together with 32 reference strains of Shewanella, Pseudomonas, Aeromonas and Alcaligenes, were phenotypically classified using 124 unit characters. Data were processed by the Simple Matching (SSM) and Jaccard (SJ) coefficients, and unweighted pair group algorithm with arithmetic averages. Fourteen clusters were defined at the 75% SJ similarity level which correspond to the SSM level of 86%. SJ-based clusters containing field strains were designated Pseudomonas fragi (cluster 1; 31% of the field strains), Ps. lundensis (cluster 2; 2% of the field strains), Ps. fluorescens biovar III (cluster 4; 4% of the field strains), Ps. putida biovar A (cluster 5; 3% of the field strains), Ps. fluorescens/putida (clusters 3 and 6; 6% of the field strains), Psychrobacter (clusters 8 and 9; 3% of the field strains), Shewanella putrefaciens (clusters 10, 11, 12 and 13; 44% of the field strains) and Aer. sobria (cluster 14; 6% of the field strains, all isolated from fresh water fish). Each field strain represented the spoilage flora of refrigerated fish at a total aerobic count of about 10(8) cfu/g. Phenotypic characteristics of major clusters are given. The four S. putrefaciens clusters may be separated by key characteristics. Shewanella putrefaciens ATCC 8071T and reference strains from sources other than fish, did not group in any of the clusters. The mol % guanine + cytosine content was on average 47.6 for cluster 10, and 45.3 for cluster 13.

Animals↗
PubMed2002

The structure of the carbohydrate backbone of the LPS from Shewanella putrefaciens CN32.

The lipopolysaccharide (LPS) from a natural rough strain of Shewanella putrefaciens CN32 was analyzed using NMR and mass spectroscopy and chemical methods, and the following structure of its carbohydrate backbone is proposed: beta-Galf-(1-->3)-beta-Gal-(1-->4)-beta-Glc-(1-->4)-alpha-DDHep2PEtN-(1-->5)-alpha-Kdo4P-(1-->6)-beta-GlcN4P-(1-->6)-alpha-GlcN1P

Carbohydrate Conformation↗
PubMed2002

Structure of the phenol-soluble polysaccharide from Shewanella putrefaciens strain A6.

The structure of the phenol-soluble polysaccharide from Shewanella putrefaciens strain A6 has been elucidated. Chemical modifications of the polymer in conjunction with 1H and 13C NMR spectroscopy, including 2D techniques, were employed in the analysis. It is concluded that the repeating unit is composed of two nine-carbon sugars as follows: -->4)-alpha-NonpA-(2-->3)-beta-Sugp-(1--> where alpha-NonpA is 5-acetamido-7-acetamidino-8-O-acetyl-3,5,7,9-tetradeoxy-L-glycero-alpha-D-galacto-non-2-ulosonic acid (8eLeg) and beta-Sugp is 2-acetamido-2,6-dideoxy-4-C-(3'-carboxamide-2',2'-dihydroxypropyl)-beta-D-galactopyranose, with the proposed name Shewanellose (She).

Magnetic Resonance Spectroscopy↗
PubMed2006

A conserved histidine in cytochrome c maturation permease CcmB of Shewanella putrefaciens is required for anaerobic growth below a threshold standard redox potential.

Shewanella putrefaciens strain 200 respires a wide range of compounds as terminal electron acceptor. The respiratory versatility of Shewanella is attributed in part to a set of c-type cytochromes with widely varying midpoint redox potentials (E'(0)). A point mutant of S. putrefaciens, originally designated Urr14 and here renamed CCMB1, was found to grow at wild-type rates on electron acceptors with high E'0 [O2, NO3-, Fe(III) citrate, MnO2, and Mn(III) pyrophosphate] yet was severely impaired for growth on electron acceptors with low E'0 [NO2-, U(VI), dimethyl sulfoxide, TMAO (trimethylamine N-oxide), fumarate, gamma-FeOOH, SO3(2-), and S2O3(2-)]. Genetic complementation and nucleotide sequence analyses indicated that the CCMB1 respiratory mutant phenotype was due to mutation of a conserved histidine residue (H108Y) in a protein that displayed high homology to Escherichia coli CcmB, the permease subunit of an ABC transporter involved in cytochrome c maturation. Although CCMB1 retained the ability to grow on electron acceptors with high E'(0), the cytochrome content of CCMB1 was <10% of that of the wild-type strain. Periplasmic extracts of CCMB1 contained slightly greater concentrations of the thiol functional group (-SH) than did the wild-type strain, an indication that the E(h) of the CCMB1 periplasm was abnormally low. A ccmB deletion mutant was unable to respire anaerobically on any electron acceptor, yet retained aerobic respiratory capability. These results suggest that the mutation of a conserved histidine residue (H108) in CCMB1 alters the redox homeostasis of the periplasm during anaerobic growth on electron acceptors with low (but not high) E'0. This is the first report of the effects of Ccm deficiencies on bacterial respiration of electron acceptors whose E'0 nearly span the entire redox continuum.

ATP-Binding Cassette Transporters↗
PubMed2002

Dissimilatory Fe(III) and Mn(IV) reduction by Shewanella putrefaciens requires ferE, a homolog of the pulE (gspE) type II protein secretion gene.

Shewanella putrefaciens strain 200 respires anaerobically on a wide range of compounds as the sole terminal electron acceptor, including ferric iron [Fe(III)] and manganese oxide [Mn(IV)]. Previous studies demonstrated that a 23.3-kb S. putrefaciens wild-type DNA fragment conferred metal reduction capability to a set of respiratory mutants with impaired Fe(III) and Mn(IV) reduction activities (T. DiChristina and E. DeLong, J. Bacteriol. 176:1468-1474, 1994). In the present study, the smallest complementing fragment was found to contain one open reading frame (ORF) (ferE) whose translated product displayed 87% sequence similarity to Aeromonas hydrophila ExeE, a member of the PulE (GspE) family of proteins found in type II protein secretion systems. Insertional mutants E726 and E912, constructed by targeted replacement of wild-type ferE with an insertionally inactivated ferE construct, were unable to respire anaerobically on Fe(III) or Mn(IV) yet retained the ability to grow on all other terminal electron acceptors. Nucleotide sequence analysis of regions flanking ferE revealed the presence of one partial and two complete ORFs whose translated products displayed 55 to 70% sequence similarity to the PulD, -F, and -G homologs of type II secretion systems. A contiguous cluster of 12 type II secretion genes (pulC to -N homologs) was found in the unannotated genome sequence of Shewanella oneidensis (formerly S. putrefaciens) MR-1. A 91-kDa heme-containing protein involved in Fe(III) reduction was present in the peripheral proteins loosely attached to the outside face of the outer membrane of the wild-type and complemented (Fer+) B31 transconjugates yet was missing from this location in Fer mutants E912 and B31 and in uncomplemented (Fer-) B31 transconjugates. Membrane fractionation studies with the wild-type strain supported this finding: the 91-kDa heme-containing protein was detected with the outer membrane fraction and not with the inner membrane or soluble fraction. These findings provide the first genetic evidence linking dissimilatory metal reduction to type II protein secretion and provide additional biochemical evidence supporting outer membrane localization of S. putrefaciens proteins involved in anaerobic respiration on Fe(III) and Mn(IV).

Amino Acid Sequence↗
PubMed2001

Uptake of choline from salmon flesh and its conversion to glycine betaine in response to salt stress in Shewanella putrefaciens.

When cultured in M63 minimal medium plus 0.6 M NaCl, the growth of Shewanella putrefaciens was strongly inhibited. The addition of an extract from smoked salmon to this medium restored the growth almost to the unstressed level. A comparison of the 13C NMR spectra of intracellular solutes extracted from S. putrefaciens cells cultured in both conditions revealed the accumulation of glycine betaine (GB) from the smoked salmon extract (SSE). Analysis of the osmoprotective properties of this extract for several strains of Escherichia coli (which differ from each other in their ability to accumulate GB (i) from the surrounding environment, and (ii) from its hydroxylated precursor choline), demonstrated the absence of GB in the SSE. From the overall results, we inferred that salt-stressed S. putrefaciens cells accumulated GB from choline present in the SSE. Furthermore, the use of [14C]-labeled betaines gave evidence that S. putrefaciens (i) oxidised choline to GB, (ii) accumulated GB as a non-metabolisable osmolyte (up to 1300 nmol (mg dw)(-1) when cultured in a medium containing 0.5 M NaCl and either 1 mM choline or 1 mM GB), and (iii) both choline and GB uptake activities were osmotically upregulated (both activities were increased more than 50-fold in media containing 0.4 to 0.6 M NaCl). In all, our results suggest that in salted smoked salmon, S. putrefaciens imports and oxidises choline, leading to the intracellular accumulation of GB.

Animals↗
PubMed1997

Replication of plasmids with the p15A origin in Shewanella putrefaciens MR-1.

The plasmid pACYC184 was introduced into Shewanella putrefaciens MR-1 by electroporation. In 100% of the transformants examined, the plasmid was maintained as a free replicon outside the chromosome. This was the case whether or not the plasmid contained a 224-bp DNA insert derived from an open-reading frame of MR-1 genomic DNA. Therefore, in contrast to a report in the literature, plasmids containing the p15A origin of replication can replicate freely in S. putrefaciens MR-1, and do not make convenient vectors for gene replacement in this bacterium. However, we found that plasmids with the pMB1 origin of replication (e.g. pBR322) cannot replicate in MR-1 and could therefore have potential as vectors for gene replacement.

Blotting, Southern↗
PubMed2001

Sorption of Fe (hydr)oxides to the surface of Shewanella putrefaciens: cell-bound fine-grained minerals are not always formed de novo.

Shewanella putrefaciens, a gram-negative, facultative anaerobe, is active in the cycling of iron through its interaction with Fe (hydr)oxides in natural environments. Fine-grained Fe precipitates that are attached to the outer membranes of many gram-negative bacteria have most often been attributed to precipitation and growth of the mineral at the cell surface. Our study of the sorption of nonbiogenic Fe (hydr)oxides revealed, however, that large quantities of nanometer-scale ferrihydrite (hydrous ferric oxide), goethite (alpha-FeOOH), and hematite (alpha-Fe(2)O(3)) adhered to the cell surface. Attempts to separate suspensions of cells and minerals with an 80% glycerin cushion proved that the sorbed minerals were tightly attached to the bacteria. The interaction between minerals and cells resulted in the formation of mineral-cell aggregates, which increased biomass density and provided better sedimentation of mineral Fe compared to suspensions of minerals alone. Transmission electron microscopy observations of cells prepared by whole-mount, conventional embedding, and freeze-substitution methods confirmed the close association between cells and minerals and suggested that in some instances, the mineral crystals had even penetrated the outer membrane and peptidoglycan layers. Given the abundance of these mineral types in natural environments, the data suggest that not all naturally occurring cell surface-associated minerals are necessarily formed de novo on the cell wall.

Adsorption↗
PubMed2002

Comparison of adhesion of the food spoilage bacterium Shewanella putrefaciens to stainless steel and silver surfaces.

AIMS: To compare the number of attached Shewanella putrefaciens on stainless steel with different silver surfaces, thus evaluating whether silver surfaces could contribute to a higher hygienic status in the food industry. METHODS AND RESULTS: Bacterial adhesion to three types of silver surface (new silver, tarnished silver and sulphide-treated silver) was compared with adhesion to stainless steel (AISI 316) using the Malthus indirect conductance method to estimate the number of cfu cm(-2). The number of attached bacteria on new silver surfaces was lower than on steel for samples taken after 24 h. However, this was not statistically significant (P > 0.05). The numbers of attached bacteria were consistently lower when tarnished silver surfaces were compared with stainless steel and some, but not all, experiments showed statistical significance (P < 0.05). Treating new silver with sulphide to reproduce a tarnished silver surface did not result in a similar lowering of adhering cells when compared with steel (P > 0.05). CONCLUSIONS: New or tarnished silver surfaces caused a slight reduction in numbers of attached bacteria; however, the difference was only sometimes statistically significant. SIGNIFICANCE AND IMPACT OF THE STUDY: The lack of reproducibility in differences in numbers adhering to the different surfaces and lack of statistical significance between numbers of adhered viable bacteria do not indicate that the tested silver surfaces can be used to improve hygienic characteristics of surfaces in the food industry.

Bacterial Adhesion↗