Phosphate starvation triggers production and secretion of an extracellular lipoprotein in Caulobacter crescentus.
Phosphate starvation triggers production and secretion of an extracellular lipoprotein in Caulobacter crescentus.
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DOI：
10.1371/journal.pone.0014198
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发表时间：
2010-12-02
期刊：
影响因子：
3.7
通讯作者：
Matroule JY
中科院分区：
文献类型：
--
作者：
Le Blastier S;Hamels A;Cabeen M;Schille L;Tilquin F;Dieu M;Raes M;Matroule JY
寡营养环境中的生活需要对突然缺乏营养物质做出快速的适应性反应。将特定的降解酶分泌到细胞外培养基中是从附近来源调动所需营养的一种手段。水生细菌新月柄杆菌必须经常面临环境的变化，例如磷酸盐限制。本文报道的证据表明，在磷酸盐饥饿下，C. crescentus 产生一种名为 ElpS 的膜表面锚定脂蛋白，随后释放到细胞外介质中。编码 II 型分泌系统 (T2SS) 的完整 12 个基因位于 C. crescentus 基因组中的 elpS 基因座附近。删除该 T2SS 会损害 ElpS 在环境中的释放，令人惊讶的是，ElpS 仍然存在于细胞表面，表明 T2SS 不参与 ElpS 到外膜的易位，而是参与其释放。因此，用蛋白酶抑制剂处理可防止ElpS在细胞外介质中的释放，这表明ElpS的分泌依赖于T2SS分泌的蛋白酶。最后，ElpS 的分泌与培养物上清液中碱性磷酸酶活性的增加相关，表明分泌的蛋白质在无机磷酸盐动员中的作用。总之，我们发现，在磷酸盐饥饿时，C. crescentus 会产生外膜结合脂蛋白 ElpS，该脂蛋白进一步裂解并以 T2SS 依赖性方式释放到细胞外介质中。我们的数据表明，ElpS 与碱性磷酸酶活性相关，从而使细菌能够从恶劣的环境中收集无机磷酸盐。
Life in oligotrophic environments necessitates quick adaptive responses to a sudden lack of nutrients. Secretion of specific degradative enzymes into the extracellular medium is a means to mobilize the required nutrient from nearby sources. The aquatic bacterium Caulobacter crescentus must often face changes in its environment such as phosphate limitation. Evidence reported in this paper indicates that under phosphate starvation, C. crescentus produces a membrane surface-anchored lipoprotein named ElpS subsequently released into the extracellular medium. A complete set of 12 genes encoding a type II secretion system (T2SS) is located adjacent to the elpS locus in the C. crescentus genome. Deletion of this T2SS impairs release of ElpS in the environment, which surprisingly remains present at the cell surface, indicating that the T2SS is not involved in the translocation of ElpS to the outer membrane but rather in its release. Accordingly, treatment with protease inhibitors prevents release of ElpS in the extracellular medium suggesting that ElpS secretion relies on a T2SS-secreted protease. Finally, secretion of ElpS is associated with an increase in alkaline phosphatase activity in culture supernatants, suggesting a role of the secreted protein in inorganic phosphate mobilization. In conlusion, we have shown that upon phosphate starvation, C. crescentus produces an outer membrane bound lipoprotein, ElpS, which is further cleaved and released in the extracellular medium in a T2SS-dependent manner. Our data suggest that ElpS is associated with an alkaline phosphatase activity, thereby allowing the bacterium to gather inorganic phosphates from a poor environment.
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