Omega-3 fatty acids (ω3 FAs) have attracted attention because they have various health benefits for humans. Fish oils are currently major sources of ω3 FAs, but a sustainable supply of ω3 FAs based on fish oils is problematic because of the increasing demand. In this study, the production potential of a genetically engineered marine cyanobacterium, Synechococcus sp. strain NKBG 15041c, was examined as an alternative source of ω3 FAs. A change in fatty acid composition of this cyanobacterium was successfully induced by the expression of a heterologous Δ6-desaturase, and the transformants synthesized stearidonic acid, which the wild type cannot produce. As a result of optimization of culture conditions, maximal contents of stearidonic acid and total ω3 FAs reached 12.2 ± 2.4 and 118.1 ± 3.5 mg/g, respectively. The maximal ω3 FA productivity was 4.6 ± 0.7 mg/(L⋅day). These are the highest values of the contents of stearidonic acid and ω3 FAs in genetically engineered cyanobacteria reported thus far. Therefore, genetically engineered Synechococcus sp. strain NKBG 15041c may be a promising sustainable source of ω3 fatty acids.
Thermoresponsive magnetic nanoparticles (MNPs) were synthesized using a magnetosome display system. An elastin-like polypeptide decamer of VPGVG (ELP), which is hydrophobic above the transition temperature ( T) and can form an insoluble aggregation, was immobilized on biogenic MNPs in the magnetotactic bacterium, Magnetospirillum magneticum AMB-1. It was suggested that hydrophobicity of the MNP surface increased at 60 °C compared with 20 °C by the immobilization of ELP. Size distribution analysis indicated that the immobilization of ELP onto MNPs induced the increased hydrophobicity with increasing temperatures up to 60 °C, promoting aggregation of the particles by hydrophobic and magnetic interactions. These results suggest that the acceleration of magnetic collection at 60 °C was caused by particle aggregation promoted by hydrophobic interaction between ELP-MNPs. Furthermore, the immobilization of ELP on MNPs gave a quick magnetic collection at 60 °C by external magnetic field. The thermoresponsive properties will further expand the utility of biotechnological applications of biogenic MNPs.
To investigate the origin of the enhanced T c (≈ 110 K) of the trilayer cuprate superconductor Bi 2 Sr 2 Ca 2 Cu 3 O 10+δ (Bi-2223), we have performed systematic magnetoresistance (MR) measurements on this superconductor, as well as on the bilayer superconductor, Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212). The in-plane coherence length, ξ ab , and the specific-heat jump, ∆C, have been estimated using the theory of renormalized superconductive fluctuations, and the doping dependence of these parameters has been qualitatively explained using the Fermi arc approach.A detailed comparison of the superconducting parameters with T c for these compounds suggests that an additional superconducting condensation energy exists, due to an increase in the number of stacking CuO 2 planes in a unit cell.
The marine cyanobacterium Synechococcus sp. strain NKBG042902 was isolated from coastal areas in Japan. Strain NKBG042902 has four plasmids: pSY8, pSY9, pSY10, and pSY11. Moreover, the hybrid plasmid pUSY02 containing pSY11 and Escherichia coli plasmid pUC18 was constructed for this strain. The genetic manipulation technique using pUSY02 was established for this strain and used in metabolic engineering. Here, we report the draft genome sequence of this strain, which has 77 contigs comprising a total length of 3,319,479 bp, with a G+C content of 49.4%.
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