Imaging mass spectrometry of intraspecies metabolic exchange revealed the cannibalistic factors of Bacillus subtilis
Imaging mass spectrometry of intraspecies metabolic exchange revealed the cannibalistic factors of Bacillus subtilis
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DOI：
10.1073/pnas.1008368107
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发表时间：
2010-09-14
影响因子：
11.1
通讯作者：
Dorrestein, Pieter C.
中科院分区：
文献类型：
--
作者：
Liu, Wei-Ting;Yang, Yu-Liang;Dorrestein, Pieter C.
在细菌同类相食的过程中，分化的亚群从基因相同的兄弟姐妹那里获取营养，以便在营养有限的条件下继续生长。假设驱动成像质谱（IMS）用于鉴定枯草芽孢杆菌同类相食系统中有活性的代谢物，该系统中产孢细胞会裂解不产孢的兄弟姐妹。鉴定了两个候选分子，它们的序列与拟同类相食因子skfA和sdpC基因的产物相匹配，并对最终产物的结构进行了分析。SKF是一种环状26个氨基酸（aa）的肽，通过一个二硫和一个半胱氨酸硫醚桥接到甲硫氨酸的α位置进行翻译后修饰，这种翻译后修饰在生物学中从未被描述过。SDP是一个有42个残基的肽，有一个二硫桥。在固体培养基上的现场试验中，过量生产的SKF和SDP具有同类相食的杀伤作用，其中SDP的效价更高。然而，在荧光显微镜和生长试验中，只有纯化的SDP对液体培养基中的枯草芽孢杆菌细胞有影响。具体而言，SDP处理以浓度依赖的方式延迟生长，导致细胞通透性增加，最终导致细胞裂解，并伴随膜小管和膜球的产生。同样，SDP能抑制病原菌金黄色葡萄球菌和表皮葡萄球菌的生长，而SKF不能，IC50与万古霉素相当。这项研究，随着SKF和SDP结构的鉴定，突出了IMS在研究微生物菌落代谢交换方面的优势，也证明了IMS是发现新的生物活性分子的有前途的方法。
During bacterial cannibalism, a differentiated subpopulation harvests nutrients from their genetically identical siblings to allow continued growth in nutrient-limited conditions. Hypothesis-driven imaging mass spectrometry (IMS) was used to identify metabolites active in a Bacillus subtilis cannibalism system in which sporulating cells lyse nonsporulating siblings. Two candidate molecules with sequences matching the products of skfA and sdpC, genes for the proposed cannibalistic factors sporulation killing factor (SKF) and sporulation delaying protein (SDP), respectively, were identified and the structures of the final products elucidated. SKF is a cyclic 26-amino acid (aa) peptide that is posttranslationally modified with one disulfide and one cysteine thioether bridged to the alpha-position of a methionine, a posttranslational modification not previously described in biology. SDP is a 42-residue peptide with one disulfide bridge. In spot test assays on solid medium, overproduced SKF and SDP enact a cannibalistic killing effect with SDP having higher potency. However, only purified SDP affected B. subtilis cells in liquid media in fluorescence microscopy and growth assays. Specifically, SDP treatment delayed growth in a concentration-dependent manner, caused increases in cell permeability, and ultimately caused cell lysis accompanied by the production of membrane tubules and spheres. Similarly, SDP but not SKF was able to inhibit the growth of the pathogens Staphylococcus aureus and Staphylococcus epidermidis with comparable IC50 to vancomycin. This investigation, with the identification of SKF and SDP structures, highlights the strength of IMS in investigations of metabolic exchange of microbial colonies and also demonstrates IMS as a promising approach to discover novel biologically active molecules.