Presentation Information
[P04-567]Evaluation of magnetic properties of magnetic particles from an engineered Magnetospirillum magneticum strain AMB-1
○Sora Mochizuki1 (1. Tokyo University Aguriculuture and Technology (Japan))
Keywords:
Biomineralization,Magnetotactic bacteria,Magnetic particles,Magnetic properties,Genetic engineering
[Purpose]
The size and shape of magnetic particles are key determinants of magnetic properties and thus critical parameters for optimizing particle performance in industrial applications. Magnetospirillum magneticum strain AMB-1 produces magnetosomes, which are membrane-enclosed magnetic particles. Previous studies demonstrated that the introduction of additional magnetosome biosynthesis genes subsequentially increased both the number and size of particles per cell relative to the wild type, however, the magnetic properties of particles produced by such engineered strains remain poorly characterized. Here, we investigated whether the morphology changes observed in particles from the engineered strains are associated with altered magnetic properties.
[Method]
A genetically engineered AMB-1 strain carries two copies of mamAB and mms6 operons and three copies of mamGFDC operons. The strain was cultivated in a medium by fed-batch culture with pH control and continuous supplementation of iron and other sources. Stationary-phase cells and magnetically recovered particles obtained after cell disruption and magnetic separation were analyzed by transmission electron microscopy (TEM). The magnetic properties of recovered particles were measured using a vibrating sample magnetometer.
[Results]
Particles recovered from the engineered strain showed approximately 1.3-fold higher coercivity than those from the wild type. TEM image analysis revealed no significant difference in mean particle size between the wild type and the engineered strains. In contrast, particles from the engineered strain showed a significantly lower shape factor, significantly higher aspect ratio, and significantly greater major axis length, whereas minor axis length remained unchanged.
[Consideration]
Our results indicate that the particles from the engineered strain were not uniformly enlarged but preferentially elongated along the major axis, resulting in increased shape anisotropy. Because coercivity is influenced not only by particle size but also by shape anisotropy, the higher coercivity observed in the engineered strain is more likely attributable to increased shape anisotropy than to an increase in mean particle size.
[Conclusion]The genetic engineering of magnetosome biosynthesis operons altered the morphology of recovered magnetic particles and increased their shape anisotropy. This morphological change may contribute to the higher coercivity observed in particles from the engineered strain.
The size and shape of magnetic particles are key determinants of magnetic properties and thus critical parameters for optimizing particle performance in industrial applications. Magnetospirillum magneticum strain AMB-1 produces magnetosomes, which are membrane-enclosed magnetic particles. Previous studies demonstrated that the introduction of additional magnetosome biosynthesis genes subsequentially increased both the number and size of particles per cell relative to the wild type, however, the magnetic properties of particles produced by such engineered strains remain poorly characterized. Here, we investigated whether the morphology changes observed in particles from the engineered strains are associated with altered magnetic properties.
[Method]
A genetically engineered AMB-1 strain carries two copies of mamAB and mms6 operons and three copies of mamGFDC operons. The strain was cultivated in a medium by fed-batch culture with pH control and continuous supplementation of iron and other sources. Stationary-phase cells and magnetically recovered particles obtained after cell disruption and magnetic separation were analyzed by transmission electron microscopy (TEM). The magnetic properties of recovered particles were measured using a vibrating sample magnetometer.
[Results]
Particles recovered from the engineered strain showed approximately 1.3-fold higher coercivity than those from the wild type. TEM image analysis revealed no significant difference in mean particle size between the wild type and the engineered strains. In contrast, particles from the engineered strain showed a significantly lower shape factor, significantly higher aspect ratio, and significantly greater major axis length, whereas minor axis length remained unchanged.
[Consideration]
Our results indicate that the particles from the engineered strain were not uniformly enlarged but preferentially elongated along the major axis, resulting in increased shape anisotropy. Because coercivity is influenced not only by particle size but also by shape anisotropy, the higher coercivity observed in the engineered strain is more likely attributable to increased shape anisotropy than to an increase in mean particle size.
[Conclusion]The genetic engineering of magnetosome biosynthesis operons altered the morphology of recovered magnetic particles and increased their shape anisotropy. This morphological change may contribute to the higher coercivity observed in particles from the engineered strain.
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