Ferroplasma thermophilum, a sort of extreme acidophilic archaea, which can synthesize intracellular cobalt ferrite nanocrystals, is investigated in this study. The nanocrystals were analyzed with ultrathin sections and transmission electron microscope, with the size of 20–60 nm, the number of more than 30 in each cell at average, which indicated that F. thermophilum can synthesize intracellular nanocrystals and also belongs to high-yield nanocrystals-producing strain. Intriguingly, the nanocrystals contain ferrite and cobalt characterized by EDS X-ray analysis, suggesting that both cobalt and ferrite are potentially contributed to the formation of nanocrystals. Moreover, under the different energy source culture conditions of FeSO₄ and CuFeS₂, the size and the morphology of the nanocrystals are different. It was also found that the higher initial Fe availability leads to an induced synthesis of larger nanocrystals and the lower oxidation-reduction potential (ORP) leads to an induced effect on the synthesis of nanocrystals with abnormal unhomogeneous size, which suggested that the higher initial Fe availability and the lower oxidation-reduction potential lead to a higher uptake efficiency of iron ions of F. thermophilum by iron and ORP gradient culture. 摘要 本文研究一种极端嗜酸古菌 Ferroplasma thermophilum 合成胞内含铁钴的纳米颗粒. 通过冷冻切片和透射电镜发现纳米颗粒的大小在 20~60 nm, 其数目在每个细胞中平均超过 30 个, 这表明 Ferroplasma thermophilum 不仅可以合成胞内纳米颗粒, 还是一种高产菌. 更有趣的是, 通过 EDS X-ray 分析表明, 纳米颗粒的元素组成包含铁与钴, 这表明铁与钴都参与了纳米颗粒的合成. 更重要的是, 在不同能源物质由硫酸亚铁与黄铜矿的培养下, 发现 Ferroplasma thermophilum 所合成的纳米颗粒大小与形态不同. 进一步研究表明, 这一现象与培养基中最初铁离子浓度和电位有关, 在高初始铁离子 浓度培养下, Ferroplasma thermophilum 所合成的纳米颗粒较大, 低电位导致纳米颗粒形态不均一, 原因在于高初始铁离子浓度与低电位促进了 Ferroplasma thermophilum 铁离子的吸收. 我们的研究丰富了磁性细菌的趋磁种类, 增加了微生物合成胞内纳米颗粒的多样性, 尤其是钴的参与.