Biosynthesis of Nanomaterials by Shewanella Species for Application in Lithium Ion Batteries

Nanomaterials exhibit extraordinary properties based on their size, shape, chemical composition, and crystal structure. Owing to their unique properties nanomaterials are preferred over their bulk counterparts for a number of applications. Although conventional physical and chemical routes were established for the massive production of nanomaterials, there are some drawbacks such as environmental burden and high cost that cannot be disregarded. Recently, there has been great interest toward the green synthesis of inorganic nanomaterials. It has been reported that dissimilatory metal reduction by microorganisms is a cost-effective process to remediate toxic organic and inorganic compounds under anaerobic conditions. Particularly, members of the Shewanella genus have been utilized to produce various biogenic nanomaterials with unique micro/nanostructured morphologies through redox transformations as well as to remove harmful metals and metalloids in eco-efficient and environment-friendly methods under ambient conditions. In the present mini-review, we specifically address the active utilization of microbial respiration processes for the synthesis of novel functional biogenic nanomaterials by the members of the Shewanella genus. This biosynthetic method may provide alternative approaches to produce electrode materials for sustainable energy storage applications

Characterization of a Self-sufficient <i>Trans</i>-Anethole Oxygenase from <i>Pseudomonas putida</i> JYR-1

<div><p>A novel flavoprotein monooxygenase, <i>trans</i>-anethole oxygenase (TAO), from <i>Pseudomonas putida</i> JYR-1, which is capable of catalyzing the oxidation of <i>trans</i>-anethole to <i>p</i>-anisaldehyde, was heterologously expressed in <i>E. coli</i> and purified. Enzymatic kinetics of diverse substrates and cofactors revealed that TAO is likely to be a novel self-sufficient flavoprotein monooxygenase. Enzyme assays of GST-TAO demonstrated that TAO catalyzed a <i>trans</i>-anethole oxidation reaction without auxiliary component enzyme-like electron-transfer flavin reductases. The single component TAO had the ability to reduce flavin cofactors and simultaneously oxidize <i>trans</i>-anthole to <i>p</i>-anisaldehyde. In the processes of reduction of flavin and oxidation of <i>trans</i>-anethole, TAO accepted various flavin and NAD(P)H cofactors. TAO also catalyzed oxidation of isoeugenol, <i>O</i>-methyl isoeugenol, and isosafrole, all of which contain the 2-propenyl functional group on the aromatic ring structure with different catalytic efficiency. TAO had the greatest catalytic efficiency (<i>k</i>_cat/<i>K</i>_m) with the original substrate, <i>trans</i>-anethole. Investigation about partially deleted mutants of TAO indicated that reductase active sites appeared to be located near the N terminal. Site directed mutagenesis studies also proved that the proposed flavin binding sites, Trp-38, Thr-43, Tyr-55, were critical for flavin reduction. However, disruption of any portion of TAO eliminated the oxygenase activity.</p></div

Draft genome sequence of Escherichia coli W26, an enteric strain isolated from cow feces

An enteric bacterium, Escherichia coli W26 (KACC 16630), was isolated from feces from a healthy cow in South Korea. Here, we report the draft genome sequence of the isolate, which is closely affiliated with commensal strains belonging to E. coli phylogroup B1.

Adsorption and Incorporation of Arsenic to Biogenic Lepidocrocite Formed in the Presence of Ferrous Iron during Denitrification by Paracoccus denitrificans

We demonstrate adsorption and partial incorporation of arsenic, in its soluble form, either as arsenite or arsenate into lepidocrocite (gamma-FeOOH), which was formed through nitrite-driven Fe(II) oxidation by Paracoccus denitrificans under nitrate-reducing conditions. Fe and As Kedge XANES and radial distribution functions of Fourier transformed EXAFS spectra showed that portions of As were found to be incorporated in the biogenic lepidocrocite, in addition to higher portions of adsorbed As. We suggest that denitrifying bacteria such as Paracoccus denitrificans, studied here, could facilitate decrease of aqueous arsenic As(III) and/or As(V) through indirect Fe(II) oxidation to solid phase iron minerals, here as lepidocrocite, by the denitrification product nitrite in the presence of nitrate, ferrous iron, and arsenic, under certain environmental conditions where these materials could be found, such as in As-contaminated paddy soils and wetland

Draft genome sequence of Escherichia coli AI27, a porcine isolate belonging to phylogenetic group B1

Escherichia coli AI27 is a putatively commensal strain isolated from feces of a pig. Here we report the draft genome sequence of E. coli AI27. This is the first porcine strain in the phylogenetic group B1 whose genome sequence has been determined.

Enantioselective Synthesis of S-Equol from Dihydrodaidzein by a Newly Isolated Anaerobic Human Intestinal Bacterium

A newly isolated rod-shaped, gram-negative anaerobic bacterium from human feces, named Julong 732, was found to be capable of metabolizing the isoflavone dihydrodaidzein to S-equol under anaerobic conditions. The metabolite, equol, was identified by using electron impact ionization mass spectrometry, (1)H and (13)C nuclear magnetic resonance spectroscopy, and UV spectral analyses. However, strain Julong 732 was not able to produce equol from daidzein, and tetrahydrodaidzein and dehydroequol, which are most likely intermediates in the anaerobic metabolism of dihydrodaidzein, were not detected in bacterial culture medium containing dihydrodaidzein. Chiral stationary-phase high-performance liquid chromatography eluted only one metabolite, S-equol, which was produced from a bacterial culture containing a racemic mixture of dihydrodaidzein. Strain Julong 732 did not show racemase activity to transform R-equol to S-equol and vice versa. Its full 16S rRNA gene sequence (1,429 bp) had 92.8% similarity to that of Eggerthella hongkongenis HKU10. This is the first report of a single bacterium capable of converting a racemic mixture of dihydrodaidzein to enantiomeric pure S-equol

NADH consumption for reducing FAD by wild-type GST-TAO (A), its mutants GST-TAO (N1–174) (B), GST-TAO (N1–104) (C), GST-TAO (N175–348) (D), point mutated GST-TAO (W38A/T43A/Y55A) (E), and negative control (F) at 0 min (▪), 30 min (•), and 60 min (▴).

<p>NADH consumption for reducing FAD by wild-type GST-TAO (A), its mutants GST-TAO (N1–174) (B), GST-TAO (N1–104) (C), GST-TAO (N175–348) (D), point mutated GST-TAO (W38A/T43A/Y55A) (E), and negative control (F) at 0 min (▪), 30 min (•), and 60 min (▴).</p

Purification of GST-TAO from <i>E. coli</i> BL21(DE3)(pGex-TAO).

<p>Purification of GST-TAO from <i>E. coli</i> BL21(DE3)(pGex-TAO).</p