Keim Carolina N, Farina Marcos
Instituto de Microbiologia Paulo de Góes, CCS, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho, 373, Cidade Universitária, Rio de Janeiro, RJ, 21941-902, Brazil.
Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho, 373, Cidade Universitária, Rio de Janeiro, RJ, Brazil.
Braz J Microbiol. 2025 Mar;56(1):155-166. doi: 10.1007/s42770-024-01584-8. Epub 2024 Dec 11.
Magnetotactic bacteria align to magnetic field lines while swimming in a behavior known as magnetotaxis. They are diverse phylogenetically and morphologically and include both unicellular and multicellular morphologies. The magnetotactic multicellular prokaryote (MMP) 'Candidatus Magnetoglobus multicellularis' has been extensively studied, even though it remains uncultured up to now. It swims back and forth along magnetic field lines, exhibiting a preferential swimming direction that is usually south-seeking, as described for most magnetotactic microorganisms from the Southern Hemisphere. In order to understand the effects of the magnetic field intensity on the backward excursions of 'Ca. M. multicellularis', we applied magnetic fields ranging from 0.09 to 3.4 mT and recorded their movements. Each microorganism was followed frame by frame generating position coordinates, which were used to calculate the frequency of reversal events, as well as the time, distance, and velocity. The velocities in forward movements before and after backward excursions are similar, but no relation was found with the velocity in backward movements. The shapes of the trajectories are distinct in forward and backward movements. In addition, the backward velocities are usually higher. The sharp changes in direction (approximately 180°) indicate that reversal of the flagella rotation direction is the probable mechanism for swimming backward. In conclusion, the backward excursions provide additional freedom of movement to the microorganism, especially when it is constrained by magnetic fields stronger than the Earth's. Backward movements integrate the 'Ca. M. multicellularis' behavioral toolbox, which includes also negative phototaxis, photokinesis, magnetotaxis and possibly helical klinotaxis.
趋磁细菌在游泳时会沿着磁力线排列，这种行为被称为趋磁作用。它们在系统发育和形态上具有多样性，包括单细胞和多细胞形态。尽管迄今尚未培养成功，但趋磁多细胞原核生物（MMP）“磁球多细胞菌（暂名）”已得到广泛研究。它沿着磁力线来回游动，表现出通常向南的优先游动方向，这与来自南半球的大多数趋磁微生物的情况相同。为了了解磁场强度对“磁球多细胞菌（暂名）”向后游动的影响，我们施加了0.09至3.4毫特斯拉的磁场并记录它们的运动。对每个微生物逐帧跟踪以生成位置坐标，这些坐标用于计算反转事件的频率以及时间、距离和速度。向后游动前后向前运动的速度相似，但未发现与向后运动的速度有相关性。向前和向后运动的轨迹形状不同。此外，向后速度通常更高。方向的急剧变化（约180°）表明鞭毛旋转方向的反转可能是向后游动的机制。总之，向后游动为微生物提供了额外的运动自由度，特别是当它受到比地球磁场更强的磁场约束时。向后运动整合了“磁球多细胞菌（暂名）”的行为工具箱，其中还包括负趋光性、光动力学、趋磁作用以及可能的螺旋斜趋性。
