Quantifying the Benefit of a Dedicated “Magnetoskeleton” in Bacterial Magnetotaxis by Live-Cell Motility Tracking and Soft Agar Swimming Assay
Quantifying the Benefit of a Dedicated “Magnetoskeleton” in Bacterial Magnetotaxis by Live-Cell Motility Tracking and Soft Agar Swimming Assay
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通过活细胞运动追踪和软琼脂游动测定来量化细菌趋磁中专用“磁骨骼”的益处
DOI：
10.1128/aem.01976-19
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发表时间：
2020
影响因子：
4.4
通讯作者：
D. Schüler
中科院分区：
文献类型：
--
作者：
Pfeiffer D;D. Schüler
甲变形杆菌gryphiswaldense具有在磁场中导航的有趣能力，这种行为被称为趋磁性，由细胞内膜包裹的磁铁矿晶体磁小体的形成所控制。磁小体通过一个专门的多部分细胞骨架（“磁骨架”）沿着细胞的运动轴成链排列；然而，对其对趋磁性的重要性的精确估计还没有报道。在这里，我们通过活细胞运动跟踪，在50 μT（反映地磁场）到400 μT的限定磁场范围内估计了缺乏各种磁骨骼成分的菌株的排列。运动追踪显示ΔmamYand ΔmamKstrains（分别组装错位链和碎片链）的趋磁性部分受损，两种蛋白质的贡献大致相等。这种缺陷反映在200 μT的磁场强度上，以达到与野生型菌株在50 μT磁场下相似的对准程度。相比之下，主要形成磁小体簇的ΔmamJstrain在任何测试的野外条件下都只能弱排列，几乎无法与非磁性突变体区分开来。大多数发现都是通过软琼脂游泳实验来证实的，该实验是基于在磁场中形成的游泳晕的扭曲程度来分析趋磁性的。运动跟踪进一步发现，在与地磁场强度相等的场强范围内，格里菲斯密氏鳉的游泳速度最高。综上所述，细菌的趋磁性和在地磁场中最有效的运动需要专门的磁骨架的磁性和磁小体的细胞内定位。在gryphiswaldense磁螺旋体中，磁小体通过复杂的细胞骨架网络在螺旋细胞中以准线性链排列，包括用于磁小体链连接和分离的肌动蛋白样MamK和适配器MamJ，以及沿最短细胞运动轴定位磁小体链的MamY。磁小体链定位被认为是有效磁导航的必要条件；然而，所有关键成分的重要性和贡献尚未在反映地磁场的定义和弱磁场中量化。采用两种不同的基于运动的方法来考虑鞭毛介导的细胞推进，我们描述了所有磁骨骼成分对趋磁性的个体益处。由于缺乏mamjm几乎无法在弱磁场中排列细胞，因此需要增加大约4倍的磁场强度来补偿mamjm的损失。综上所述，磁骨架和磁小体链的优化定位是实现高效趋磁的必要条件。
The alphaproteobacterium Magnetospirillum gryphiswaldense has the intriguing ability to navigate within magnetic fields, a behavior named magnetotaxis, governed by the formation of magnetosomes, intracellular membrane-enveloped crystals of magnetite. Magnetosomes are aligned in chains along the cell’s motility axis by a dedicated multipart cytoskeleton (“magnetoskeleton”); however, precise estimates of its significance for magnetotaxis have not been reported. Here, we estimated the alignment of strains deficient in various magnetoskeletal constituents by live-cell motility tracking within defined magnetic fields ranging from 50 μT (reflecting the geomagnetic field) up to 400 μT. Motility tracking revealed that ΔmamYand ΔmamKstrains (which assemble mispositioned and fragmented chains, respectively) are partially impaired in magnetotaxis, with approximately equal contributions of both proteins. This impairment was reflected by a required magnetic field strength of 200 μT to achieve a similar degree of alignment as for the wild-type strain in a 50-μT magnetic field. In contrast, the ΔmamJstrain, which predominantly forms clusters of magnetosomes, was only weakly aligned under any of the tested field conditions and could barely be distinguished from a nonmagnetic mutant. Most findings were corroborated by a soft agar swimming assay to analyze magnetotaxis based on the degree of distortion of swim halos formed in magnetic fields. Motility tracking further revealed that swimming speeds of M. gryphiswaldense are highest within the field strength equaling the geomagnetic field. In conclusion, magnetic properties and intracellular positioning of magnetosomes by a dedicated magnetoskeleton are required and optimized for bacterial magnetotaxis and most efficient locomotion within the geomagnetic field.IMPORTANCEIn Magnetospirillum gryphiswaldense, magnetosomes are aligned in quasi-linear chains in a helical cell by a complex cytoskeletal network, including the actin-like MamK and adapter MamJ for magnetosome chain concatenation and segregation and MamY to position magnetosome chains along the shortest cellular axis of motility. Magnetosome chain positioning is assumed to be required for efficient magnetic navigation; however, the significance and contribution of all key constituents have not been quantified within defined and weak magnetic fields reflecting the geomagnetic field. Employing two different motility-based methods to consider the flagellum-mediated propulsion of cells, we depict individual benefits of all magnetoskeletal constituents for magnetotaxis. Whereas lack ofmamJresulted almost in an inability to align cells in weak magnetic fields, an approximately 4-fold-increased magnetic field strength was required to compensate for the loss ofmamKormamY. In summary, the magnetoskeleton and optimal positioning of magnetosome chains are required for efficient magnetotaxis.
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DOI：
10.1073/pnas.1701644114
发表时间：
2017-06-13
影响因子：
11.1
作者：
Kuehn, Marco J.;Schmidt, Felix K.;Thormann, Kai M.
通讯作者：
Thormann, Kai M.
影响因子：
5
作者：
D. Solaiman;R. Ashby;T. Foglia
通讯作者：
D. Solaiman;R. Ashby;T. Foglia
趋磁细菌磁螺菌 AMB-1 中磁偶极矩与细胞轴之间的错位
影响因子：
2
作者：
Lucas Le Nagard;Liu Yu;Murtuza Rajkotwala;Solomon Barkley;D. Bazylinski;A. Hitchcock;C. Fradin
通讯作者：
C. Fradin
磁螺菌 gryphiswaldense 中鞭毛蛋白基因 flaA 的失活导致缺乏鞭毛丝的非趋磁突变体
影响因子：
4.4
作者：
D. Schultheiss;M. Kube;D. Schüler
通讯作者：
D. Schüler
基于 Cre-lox 的 Magnetospirillum gryphiswaldense 基因组磁小体岛内大缺失生成方法
影响因子：
4.4
作者：
S. Ullrich;D. Schüler
通讯作者：
D. Schüler