Functional analysis of the magnetosome island in Magnetospirillum gryphiswaldense: the mamAB operon is sufficient for magnetite biomineralization.
Functional analysis of the magnetosome island in Magnetospirillum gryphiswaldense: the mamAB operon is sufficient for magnetite biomineralization.
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DOI：
10.1371/journal.pone.0025561
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发表时间：
2011
期刊：
影响因子：
3.7
通讯作者：
Schüler D
中科院分区：
文献类型：
--
作者：
Lohsse A;Ullrich S;Katzmann E;Borg S;Wanner G;Richter M;Voigt B;Schweder T;Schüler D
细菌磁小体是一种被膜包裹的纳米级磁铁矿晶体，具有趋磁导航功能。所有参与这些细胞器合成的基因都位于一个保守的基因组磁小体岛（MAI）。我们进行了一个全面的生物信息学，蛋白质组学和遗传分析的MAI在磁gryphiswaldense。通过构建大的缺失突变体，我们证明了整个区域都是生长的，大多数MAI基因在磁小体形成中没有可检测的功能，可以被消除而没有任何影响。只有不到25%的区域包含四个主要的操纵子可以与磁铁矿生物矿化，这与这些基因的高表达和它们在趋磁细菌中的保守性有关。而只有删除的mamAB操纵子导致磁性颗粒的完全丧失，删除保守的mms6，mamGFDC，和mamXY操纵子导致磁铁矿晶体的形态，大小和组织的严重缺陷。然而，这些操纵子一起被消除的菌株保留了合成小的不规则微晶的能力，并且在磁场中弱排列。这表明，虽然mamGFDC，mms6和mamXY操纵子具有关键的和部分重叠的功能，形成功能磁小体，mamAB操纵子是唯一的区域的MAI，这是必要的和足够的磁铁矿生物矿化。我们的数据进一步减少了已知的磁小体形成所需的最小基因集，并将有助于未来的基因组工程方法。
Bacterial magnetosomes are membrane-enveloped, nanometer-sized crystals of magnetite, which serve for magnetotactic navigation. All genes implicated in the synthesis of these organelles are located in a conserved genomic magnetosome island (MAI). We performed a comprehensive bioinformatic, proteomic and genetic analysis of the MAI in Magnetospirillum gryphiswaldense. By the construction of large deletion mutants we demonstrate that the entire region is dispensable for growth, and the majority of MAI genes have no detectable function in magnetosome formation and could be eliminated without any effect. Only <25% of the region comprising four major operons could be associated with magnetite biomineralization, which correlated with high expression of these genes and their conservation among magnetotactic bacteria. Whereas only deletion of the mamAB operon resulted in the complete loss of magnetic particles, deletion of the conserved mms6, mamGFDC, and mamXY operons led to severe defects in morphology, size and organization of magnetite crystals. However, strains in which these operons were eliminated together retained the ability to synthesize small irregular crystallites, and weakly aligned in magnetic fields. This demonstrates that whereas the mamGFDC, mms6 and mamXY operons have crucial and partially overlapping functions for the formation of functional magnetosomes, the mamAB operon is the only region of the MAI, which is necessary and sufficient for magnetite biomineralization. Our data further reduce the known minimal gene set required for magnetosome formation and will be useful for future genome engineering approaches.