Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing 100029, China.
Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China.
FEMS Microbiol Ecol. 2023 Nov 13;99(12). doi: 10.1093/femsec/fiad150.
Magnetotactic bacteria (MTB) have the remarkable capability of producing intracellularly membrane-enveloped magnetic nanocrystals (i.e. magnetosomes) and swimming along geomagnetic field lines. Despite more than 50 years of research, bacterial diversity and magnetosome biomineralization within MTB are relatively less known in the Gammaproteobacteria class than other groups. This is incompatible with the status of Gammaproteobacteria as the most diverse class of gram-negative bacteria with a number of ecologically important bacteria. Here, we identify a novel MTB strain YYHR-1 affiliated with the Gammaproteobacteria class of the Pseudomonadota phylum from a freshwater lake. In YYHR-1, most magnetosome crystals are organized into a long chain aligned along the cell long axis; unusually, a few small superparamagnetic crystals are located at the side of the chain, off the main chain axis. Micromagnetic simulations indicate that magnetostatic interactions among adjacent crystals within a chain reduce the Gibbs energy to enhance chain stability. Genomic analysis suggests that duplication of magnetosome gene clusters may result in off-chain magnetosomes formation. By integrating available genomic data from Gammaproteobacteria, the phylogenetic position of MTB in this class is reassigned here. Our new findings expand knowledge about MTB diversity and magnetosome biomineralization, and deepen understanding of the phylogenetics of the Gammaproteobacteria.
趋磁细菌（MTB）具有在细胞内产生膜包裹的磁性纳米晶体（即磁小体）并沿着地磁场线游动的显著能力。尽管已经进行了 50 多年的研究，但与其他群体相比，在γ变形菌门的γ变形菌中，细菌多样性和 MTB 中的磁小体生物矿化相对较少。这与γ变形菌作为革兰氏阴性菌中最多样化的类群的地位以及许多具有重要生态意义的细菌的地位是不相容的。在这里，我们从一个淡水湖中鉴定出一种新型的趋磁细菌菌株 YYHR-1，该菌株属于γ变形菌门的假单胞菌目。在 YYHR-1 中，大多数磁小体晶体组织成一条沿着细胞长轴排列的长链；不同寻常的是，少数小超顺磁晶体位于链的一侧，偏离主链轴。微磁模拟表明，链内相邻晶体之间的静磁相互作用会降低吉布斯能，从而增强链的稳定性。基因组分析表明，磁小体基因簇的重复可能导致了链外磁小体的形成。通过整合来自γ变形菌的可用基因组数据，我们重新分配了该类群中 MTB 的系统发育位置。我们的新发现扩展了关于 MTB 多样性和磁小体生物矿化的知识，并加深了对γ变形菌系统发育的理解。
