Magnetotactic bacteria are aquatic microorganisms with the ability to biomineralise membrane-enclosed magnetic nanoparticles, called magnetosomes. These magnetosomes are arranged into a chain that behaves as a magnetic compass, allowing the bacteria to align in and navigate along the Earth's magnetic field lines. According to the magneto-aerotactic hypothesis, the purpose of producing magnetosomes is to provide the bacteria with a more efficient movement within the stratified water column, in search of the optimal positions that satisfy their nutritional requirements. However, magnetosomes could have other physiological roles, as proposed in this work. Here we analyse the role of magnetosomes in the tolerance of Magnetospirillum gryphiswaldense MSR-1 to transition metals (Co, Mn, Ni, Zn, Cu). By exposing bacterial populations with and without magnetosomes to increasing concentrations of metals in the growth medium, we observe that the tolerance is significantly higher when bacteria have magnetosomes. The resistance mechanisms triggered in magnetosome-bearing bacteria under metal stress have been investigated by means of x-ray absorption near edge spectroscopy (XANES). XANES experiments were performed both on magnetosomes isolated from the bacteria and on the whole bacteria, aimed to assess whether bacteria use magnetosomes as metal storages, or whether they incorporate the excess metal in other cell compartments. Our findings reveal that the tolerance mechanisms are metal-specific: Mn, Zn and Cu are incorporated in both the magnetosomes and other cell compartments; Co is only incorporated in the magnetosomes, and Ni is incorporated in other cell compartments. In the case of Co, Zn and Mn, the metal is integrated in the magnetosome magnetite mineral core.

中文翻译：

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磁小体可能是抵抗趋磁细菌中金属应力的防护罩

趋磁细菌是水生微生物，具有生物矿化膜包裹的磁性纳米颗粒（称为磁小体）的能力。这些磁小体排列成一条链，就像一个磁罗盘，使细菌能够排列并沿着地球的磁力线行进。根据磁-气假说，产生磁小体的目的是使细菌在分层水柱内更有效地运动，以寻找满足其营养需求的最佳位置。但是，如这项工作中所提出的，磁小体可能还具有其他生理作用。在这里，我们分析了磁小体在耐磁螺旋藻中的作用。MSR-1过渡金属（Co，Mn，Ni，Zn，Cu）。通过将带有或不带有磁小体的细菌种群暴露于生长培养基中不断增加的金属浓度，我们观察到当细菌具有磁小体时，其耐受性明显更高。已经通过X射线吸收近边缘光谱法（XANES）研究了在金属应力下含磁小体的细菌中引发的耐药机制。XANES实验是针对从细菌中分离出的磁小体以及对整个细菌进行的，目的是评估细菌是否将磁小体用作金属储存器，或者它们是否在其他细胞隔室中掺入了过量的金属。我们的发现表明，耐受机制是金属特异性的：Mn，Zn和Cu既被掺入了磁小体，也被掺入了其他细胞隔室。Co仅掺入磁小体，Ni掺入其他细胞室。在Co，Zn和Mn的情况下，金属被整合在磁小体磁铁矿矿物芯中。