New violet 3,3′-bipyridyl pigment purified from deep-sea microorganism <Emphasis Type="Italic">Shewanella violacea</Emphasis> DSS12

We have purified a new violet pigment derived from Shewanella violacea DSS12 to determine its chemical structure. The pigment colored blue in tetrahydrofuran (THF) or chloroform and showed a broad absorption spectrum from 500 to 700 nm. X-ray diffraction analysis of single crystals showed that the chemical structure of this pigment was 5,5′-didodecylamino-4,4′-dihydroxy-3,3′-diazodiphenoquinone-(2,2′), containing the same chromophore as an indigoidine known as microbial blue pigment. The violet color of this pigment was due to hypsochromic shift (blue shift) caused by the side-by-side orientation of this pigment molecule, revealed by X-ray structural analyses of a single crystal. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

厌氧条件下希瓦氏菌腐殖质还原对偶氮还原的影响

以希瓦氏菌属的3个代表种为研究对象,研究了在厌氧条件下腐殖质的存在对偶氮还原的影响。实验结果表明:3个代表菌株在厌氧条件下都有高效的偶氮还原和腐殖质还原功能,1mmol/L偶氮染料在24h内完全脱色,并且偶氮还原与电子供体氧化存在着紧密的偶联关系。腐殖质物质模式物2-磺酸蒽醌AQS在小于1~2mmol/L条件下能显著加速偶氮还原,12h就完全脱色,3mmol/L时18h完全脱色。但当浓度大于3mmol/L时则对偶氮还原产生明显抑制作用。另一腐殖质模式物2,6-双磺酸蒽醌AQDS其浓度在1~3mmol/L以内亦使脱色在12h内完成,4~6mmol/L时15h左右完成脱色。7~12mmol/L仍有一定的脱色促进作用,但随着浓度的提高,其促进作用也逐渐减弱。这说明腐殖质的确可以作为氧化还原中间体穿梭于电子供体与染料的偶氮双键之间促进偶氮还原。但当其浓度达到某一阈值时它就显出与偶氮键竞争电子的本质,从而使偶氮还原速率下降。原因在于他们的氧化还原电势的差异,导致细菌呼吸链的电子递体对腐殖质物质和偶氮键的亲和力不同,从而使不同腐殖质浓度对偶氮键还原产生了不同的影响。     

A novel ICE in the genome of Shewanella putrefaciens W3-18-1: comparison with the SXT/R391 ICE-like elements

A novel R391-like ICE (integrating conjugative element) has been detected in the 4.2 MB genome of Shewanella putrefaciens W3-18-1 located on three different contigs. Assembly of the ICE encoding contigs based on similarity with R391 revealed a mosaic element of plasmid, phage and transposon-like sequences typical of SXT/R391 ICE-like elements. The element, which is 110 057 bp in length, was highly similar to R391 sequences, with most related ORFs showing >96% amino acid sequence identity. The element, designated ICESpuPO1, contained a number of inserts determining resistance to copper and other heavy metals and a broad-spectrum RND efflux pump similar to antibiotic efflux systems. The element was integrated into the Shewanella prfC gene in a manner similar to related ICE-like elements. The chromosomal element junctions contained a 17-bp SXT/R391-like attL and attR site and an unannotated ORF between attL and the ICE integrase encoding a putative recombinational directional factor necessary for excision, with 100% amino acid identity to the R391 ORF4 product.     

Simultaneous analysis of physiological and electrical output changes in an operating microbial fuel cell with Shewanella oneidensis

Changes in metabolism and cellular physiology of facultative anaerobes during oxygen exposure can be substantial, but little is known about how these changes connect with electrical current output from an operating microbial fuel cell (MFC). A high‐throughput voltage based screening assay (VBSA) was used to correlate current output from a MFC containing Shewanella oneidensis MR‐1 to carbon source (glucose or lactate) utilization, culture conditions, and biofilm coverage over 250 h. Lactate induced an immediate current response from S. oneidensis MR‐1, with both air‐exposed and anaerobic anodes throughout the duration of the experiments. Glucose was initially utilized for current output by MR‐1 when cultured and maintained in the presence of air. However, after repeated additions of glucose, the current output from the MFC decreased substantially while viable planktonic cell counts and biofilm coverage remained constant suggesting that extracellular electron transfer pathways were being inhibited. Shewanella maintained under an anaerobic atmosphere did not utilize glucose consistent with literature precedents. Operation of the VBSA permitted data collection from nine simultaneous S. oneidensis MR‐1 MFC experiments in which each experiment was able to demonstrate organic carbon source utilization and oxygen dependent biofilm formation on a carbon electrode. These data provide the first direct evidence of complex cellular responses to electron donor and oxygen tension by Shewanella in an operating MFC at select time points. Biotechnol. Bioeng. 2009;103: 524–531. Published 2009 Wiley Periodicals, Inc.     

Prokaryotes and the input of polyunsaturated fatty acids to the marine food web

The investigation of prokaryotes in aquatic ecology is often limited to their role in nutrient cycling and the degradation of organic matter. While this aspect of the microbial loop is undoubtedly important, further aspects of bacterial roles in marine food webs exist which have not been fully considered in light of recent research in related fields. The concept of bacteria providing essential nutrients may derive importance from two aspects of their role in the marine environment; firstly as a primary food source for omnivorous, sestonivorous and filtering benthic animals and secondly as components of the commensal microbial communities of marine animals. Many marine organisms lack the de novo ability to produce n-3 polyunsaturated fatty acids (PUFA) and hence rely on a dietary supply of PUFA. The issue of PUFA origin in the marine food web is particularly salient in light of recent research demonstrating the influence of PUFA levels on the efficiency of energy transfer between trophic levels. The assumption that microalgae provide the bulk of de novo PUFA production for all marine food webs must be actively reviewed with respect to particular microbial niches such as sea ice, marine animals and abyssal communities.     

Shewanella sp. GA-22, a psychrophilic hydrocarbonoclastic antarctic bacterium producing polyunsaturated fatty acids

AIMS: The effects of different growth media and temperature on production of polyunsaturated fatty acids (PUFA) by Shewanella sp. GA-22 were investigated. The attempts to characterize the GA-22 genes, homologous to those of PUFA biosynthesis gene cluster, was performed. METHODS AND RESULTS: Physiological and phylogenetic characterization of new Antarctic isolate GA-22 was performed. Total fatty acids were isolated from the cells growing under different conditions and analysed by gas chromatography-mass spectrometry (GC-MS). Using degenerated primers derived from the conserved regions within PUFA fatty acid synthase operons, five fragments of homological genes were amplified from GA-22 DNA, and two of them corresponding to pfaA and pfaC synthase subunits were sequenced. CONCLUSIONS: Strain GA-22 was shown to be able to produce three different PUFA: linoleic, arachidonic and eicosapentaenoic acids. The PUFA production was temperature- and carbon source-dependent. The deduced gene products exhibited high similarity to corresponding fatty acid synthases PfaA and PfaC. SIGNIFICANCE AND IMPACT OF STUDY: The PUFA production was detected on media supplemented with crude oil, gasoline and n-tetradecane. The apparent conservation of PUFA genes may point to the potential utilization of designed primers as functional markers in culture-independent ecological studies, and for initial screening in biotechnological fields.     

Characterization and multiple molecular forms of TorD from Shewanella massilia,the putative chaperone of the molybdoenzyme TorA

Several bacteria use trimethylamine N-oxyde (TMAO) as an exogenous electron acceptor for anaerobic respiration. This metabolic pathway involves expression of the tor operon that codes for a periplasmic molybdopterin-containing reductase of the DMSO/TMAO family, a pentahemic c-type cytochrome, and the TorD cytoplasmic chaperone, possibly required for acquisition of the molybdenum cofactor and translocation of the reductase by the twin-arginine translocation system. In this report, we show that the TorD chaperone from Shewanella massilia forms multiple and stable oligomeric species. The monomeric, dimeric, and trimeric forms were purified to homogeneity and characterized by analytical ultracentrifugation. Small-angle X-ray scattering (SAXS) and preliminary diffraction data indicated that the TorD dimer is made of identical protein modules of similar size to the monomeric species. Interconversion of the native oligomeric forms occurred at acidic pH value. In this condition, ANS fluorescence indicates a non-native conformation of the polypeptide chain in which, according to the circular dichroism spectra, the alpha-helical content is similar to that of the native species. Surface plasmon resonance showed that both the monomeric and dimeric species bind the mature TorA enzyme, but that the dimer binds its target protein more efficiently. The possible biologic significance of these oligomers is discussed in relation to the chaperone activity of TorD, and to the ability of another member of the TorD family to bind the Twin Arginine leader sequences of the precursor of DMSO/TMAO reductases.     

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).     

Arabinan degrading enzymes from Aspergillus nidulans: Induction and purification

Abstract The expression and distribution of ferric reductase activity was examined in Shewanella putrefaciens MR-1. Formate-dependent ferric reductase was not detected in aerobically grown cells but was readily detectable in anaerobically grown cells. Ferric reductase activity was found exclusively in the membrane fractions, with 54–56% in the outer membrane. In contrast, the majority of formate dehydrogenase was in the soluble fraction with lesser amounts associated with the various membrane fractions. Outer membrane ferric reductase activity was markedly inhibited by p -chloromercuriphenylsulfonate, 2-heptyl-4-hydroxyquinolone- N -oxide, and antimycin A, but was unaffected by the presence of alternate electron acceptors (nitrate, nitrite, fumarate, and trimethylamine N -oxide). Both formate and NADH served as electron donors for ferric reductase; activity with l -lactate or NADPH was poor. The addition of FMN markedly stimulated formate- and NADH-dependent ferric reductase.