A plasmid, pTA163, in Escherichia coli contained an approximately 34-kb gene fragment from Pseudomonas putida JYR-1 that included the genes responsible for the metabolism of trans-anethole to protocatechuic acid. Three Tn5-disrupted open reading frame 10 (ORF 10) mutants of plasmid pTA163 lost their abilities to catalyze trans-anethole. Heterologously expressed ORF 10 (1,047 nucleotides [nt]) under a T7 promoter in E. coli catalyzed oxidative cleavage of a propenyl group of trans-anethole to an aldehyde group, resulting in the production of para-anisaldehyde, and this gene was designated tao (trans-anethole oxygenase). The deduced amino acid sequence of TAO had the highest identity (34%) to a hypothetical protein of Agrobacterium vitis S4 and likely contained a flavin-binding site. Preferred incorporation of an oxygen molecule from water into p-anisaldehyde using (18)O-labeling experiments indicated stereo preference of TAO for hydrolysis of the epoxide group. Interestingly, unlike the narrow substrate range of isoeugenol monooxygenase from Pseudomonas putida IE27 and Pseudomonas nitroreducens Jin1, TAO from P. putida JYR-1 catalyzed isoeugenol, O-methyl isoeugenol, and isosafrole, all of which contain the 2-propenyl functional group on the aromatic ring structure. Addition of NAD(P)H to the ultrafiltered cell extracts of E. coli (pTA163) increased the activity of TAO. Due to the relaxed substrate range of TAO, it may be utilized for the production of various fragrance compounds from plant phenylpropanoids in the future.
Eco‐efficient biogenic strategies for the removal of toxic elements result in the formation of unique nano/microstructured materials with dual functionalities for energy conversion and storage. In one pot under aqueous conditions, the bacterium Shewanella sp. strain HN‐41 precipitates nanostructured arsenic sulfides (realgar, As 4 S 4 ) and its reduced graphene oxide nanocomposites. Considering the unique structural characteristics of the freestanding molecular‐cage‐like single clusters, the biogenic realgar structure is utilized as an independent anode unit since each cluster integrates four faceted five‐membered As 4 S 4 rings, providing a short diffusion length into each cluster and facile chemical binding onto the sulfur atoms with lone pairs of electrons. Here, the role of the biogenic realgar structure in the reversible uptake and release of Li ions into and from the molecular‐cage‐like single clusters is investigated. Using in situ As K‐edge X‐ray absorption fine structure analyses, the Li‐ion uptake ability of realgar As 4 S 4 (As 4 S 4 ↔Li 20 As 4 S 4 ) is achieved through a two‐step mechanism: (1) molecular clustering to form Li 8 As 4 S 4 (≈500 mA h g −1 ) and (2) alloying to form Li 12 As 4 only in the interior of the single clusters (≈750 mA h g −1 ). Thus, the bacteria‐driven biological synthesis under mild conditions can provide an alternative synthetic strategy and promotes easy scale‐up for nanostructured materials.
Here we report a peptide directed synthesis of co-shell nanocables by sequential guide formation of silica insulating shells on metallic gold nanoribbons which is significant since it demonstrated the ability to fabricate a functional nano-electronic component using a biomimetic method.
From July to August 2010, the IBRV ARAON journeyed to the Pacific sector of the Arctic Ocean to monitor bacterial variation in Arctic summer surface-waters, and temperature, salinity, fluorescence, and nutrient concentrations were determined during the ice-melting season. Among the measured physicochemical parameters, we observed a strong negative correlation between temperature and salinity, and consequently hypothesized that the melting ice decreased water salinity. The bacterial community compositions of 15 samples, includicng seawater, sea-ice, and melting pond water, were determined using a pyrosequencing approach and were categorized into three habitats: (1) surface seawater, (2) ice core, and (3) melting pond. Analysis of these samples indicated the presence of local bacterial communities; a deduction that was further corroborated by the discovery of seawater- and ice-specific bacterial phylotypes. In all samples, the Alphaproteobacteria, Flavobacteria, and Gammaproteobacteria taxa composed the majority of the bacterial communities. Among these, Alphaproteobacteria was the most abundant and present in all samples, and its variation differed among the habitats studied. Linear regression analysis suggested that changes in salinity could affect the relative proportion of Alphaproteobacteria in the surface water. In addition, the species-sorting model was applied to evaluate the population dynamics and environmental heterogeneity in the bacterial communities of surface mixed layer in the Arctic Ocean during sea-ice melting.
Summary An increase in concentration of atmospheric CO 2 is one major factor influencing global climate change. Among the consequences of such an increase is the stimulation of plant growth and productivity. Below‐ground microbial processes are also likely to be affected indirectly by rising atmospheric CO 2 levels, through increased root growth and rhizodeposition rates. Because changes in microbial community composition might have an impact on symbiotic interactions with plants, the response of root nodule symbionts to elevated atmospheric CO 2 was investigated. In this study we determined the genetic structure of 120 Rhizobium leguminosarum bv. trifolii isolates from white clover plants exposed to ambient (350 μmol mol −1 ) or elevated (600 μmol mol −1 ) atmospheric CO 2 concentrations in the Swiss FACE (Free‐Air‐Carbon‐Dioxide‐Enrichment) facility. Polymerase Chain Reaction (PCR) fingerprinting of genomic DNA showed that the isolates from plants grown under elevated CO 2 were genetically different from those isolates obtained from plants grown under ambient conditions. Moreover, there was a 17% increase in nodule occupancy under conditions of elevated atmospheric CO 2 when strains of R. leguminosarum bv. trifolii isolated from plots exposed to CO 2 enrichment were evaluated for their ability to compete for nodulation with those strains isolated from ambient conditions. These results indicate that a shift in the community composition of R. leguminosarum bv. trifolii occurred as a result of an increased atmospheric CO 2 concentration, and that elevated atmospheric CO 2 affects the competitive ability of root nodule symbionts, most likely leading to a selection of these particular strains to nodulate white clover.
O-methylation mediated by O-methyltransferases (OMTs) is a common modification in natural product biosynthesis and contributes to diversity of secondary metabolites. OMTs use phenylpropanoids, flavonoids, other phenolics and alkaloids as substrates, and share common domains for S-adenosyl-L-methionine (AdoMet) and substrate binding. We searched Arabiposis genome and found 17 OMTs genes (AtOMTs). AdoMet- and substrate-binding sites were predicted. AdoMet binding domain of AtOMTs is highly conserved, while substrate-binding domain is diverse, indicating use of different substrates. In addition, expressions of six AtOMT genes in response to UV and in different tissues were investigated using real-time quantitative reverse transcriptase-polymerase chain reaction. All the AtOMTs investigated were expressed under normal growth condition and most, except AtOMT10, were induced after UV illumination. AtOMT1 and AtOMT8 were expressed in all the tissues, whereas AtOMT10 showed flower-specific expression. Analysis of these AtOMT gene expressions could provide some clues on AtOMT involvement in the cellular processes.
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