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In natural indigo dyeing, the water-insoluble indigo included in the composted indigo leaves called sukumois converted to water-soluble leuco-indigo through the reduction activities of microorganisms under alkaline conditions. To understand the relationship between indigo reduction and microorganisms in indigo-fermentation suspensions, we isolated and identified the microorganisms that reduce indigo and analyzed the microbiota in indigo-fermentation suspensions. Indigo-reducing microorganisms, which were not isolated by means of a conventional indigo carmine-reduction assay method, were isolated by using indigo as a direct substrate and further identified and characterized. We succeeded in isolating bacteria closely related to Corynebacterium glutamicum, Chryseomicrobium aureum, and Enterococcussp. for the first time. Anthraquinone was found to be an effective mediator that facilitated the indigo-reduction activity of the isolated strains. On analysis of the microbiota in indigo-fermentation suspensions, the ratio of indigo-reducing bacteria and others was found to be important for maintaining the indigo-reduction activity.Graphical AbstractThe new indigo-reducing bacteria were isolated by the novel method from the indigo fermentation suspensions. The dyeing activities were explained by the analysis of microbiota.

We have investigated the dependence of the magnetization switching behavior on the structure, size and nonmagnetic Cu layer thickness (tCu) in Ni/Cu/M (M =Ni, Co) cylindrical nanowires fabricated by electrodeposition using porous polycarbonate templates. The crystal structure of the Ni nanowires was (111)- or (200)-oriented polycrystalline fcc, while that of Co nanowires was (100)- or (101)-oriented hcp and/or (111)-oriented polycrystalline fcc. When the wire diameter (d) was 50 nm, the squareness ratio (Mr/Ms) for M =Ni, as estimated from the magnetization curve, is almost constant at Mr/Ms∼0.79 (Mr/Ms∼0.64 for M =Co) when tCuincreases from 0 to 500 nm. When d=100nm, Mr/Msdecreases by 41% from 0.71 to 0.42 with increasing tCufrom 0 to 700 nm for M =Ni, while Mr/Msdecreases by 25% from 0.53 to 0.40 with varying tCufrom 0 to 500 nm for M =Co. The threshold Cu layer thickness (tCuth) beyond which Mr/Msbecomes constant at d=100nmis ∼500 nm for M =Ni and ∼300 nm for M =Co. The results are qualitatively consistent with those obtained from our micromagnetic simulation and analysis. The observed difference in the tCuthdependence of Mr/Msbetween M =Ni and Co is attributed to the change in the magnetic domain structure of the nanowires as it sensitively varies with the magnetocrystalline anisotropy. On the other hand, the coercive force of the nanowires shows a small tCudependence for both d=50and 100 nm. These results indicate that the layered structure in the nanowires governs the magnetic domain structure, though the effect on the magnetization switching behavior is indeed relatively small.