SAR11 lipid renovation in response to phosphate starvation
SAR11 lipid renovation in response to phosphate starvation
复制标题
DOI：
10.1073/pnas.1505034112
复制
发表时间：
2015-06-23
影响因子：
11.1
通讯作者：
Giovannoni, Stephen J.
中科院分区：
文献类型：
--
作者：
Carini, Paul;Van Mooy, Benjamin A. S.;Giovannoni, Stephen J.
浮游植物栖息在贫营养的海洋环流中，通过用缺乏磷的磷脂替代极性膜磷脂来主动减少对磷的需求。虽然非磷脂质的合成在一些异养细菌谱系中得到了很好的证明，但贫营养海洋化能异养生物中的无磷脂质合成尚未得到直接证明，这意味着它们在磷酸盐耗尽的生态系统中处于不利地位，相对于浮游植物。在这里，我们显示SAR 11进化枝化学异养Pelagibacter sp. str. HTCC 7211翻新膜脂时，磷酸盐饥饿取代一部分的磷脂与单葡萄糖和葡萄糖醛酸二酰基甘油，并通过合成新的鸟氨酸脂质。用过量磷酸盐生长的细胞的脂质谱完全由磷脂组成。相反，高达40%的总脂质转化为非磷脂质时，细胞被饥饿的磷酸盐，或甲基膦酸盐生长。依次受到磷酸盐和甲基膦酸盐限制的细胞将>75%的脂质转化为无磷类似物。在磷酸盐饥饿期间，一个四基因簇显著上调，可能编码负责脂质更新的酶。这些基因在从磷酸盐缺乏的海洋环流中分离的Pelagiorales菌株中发现，但在沿海环境的其他菌株中没有发现，这表明交替脂质合成是对磷酸盐缺乏的一种特定适应。在其他海洋α-变形菌的基因组中也发现了类似的基因簇，这意味着脂质更新是异养细胞在贫营养栖息地减少磷需求的常见策略。
Phytoplankton inhabiting oligotrophic ocean gyres actively reduce their phosphorus demand by replacing polar membrane phospholipids with those lacking phosphorus. Although the synthesis of nonphosphorus lipids is well documented in some heterotrophic bacterial lineages, phosphorus-free lipid synthesis in oligotrophic marine chemoheterotrophs has not been directly demonstrated, implying they are disadvantaged in phosphate-deplete ecosystems, relative to phytoplankton. Here, we show the SAR11 clade chemoheterotroph Pelagibacter sp. str. HTCC7211 renovates membrane lipids when phosphate starved by replacing a portion of its phospholipids with monoglucosyl- and glucuronosyl-diacylglycerols and by synthesizing new ornithine lipids. Lipid profiles of cells grown with excess phosphate consisted entirely of phospholipids. Conversely, up to 40% of the total lipids were converted to nonphosphorus lipids when cells were starved for phosphate, or when growing on methylphosphonate. Cells sequentially limited by phosphate and methylphosphonate transformed >75% of their lipids to phosphorus-free analogs. During phosphate starvation, a four-gene cluster was significantly up-regulated that likely encodes the enzymes responsible for lipid renovation. These genes were found in Pelagibacterales strains isolated from a phosphate-deficient ocean gyre, but not in other strains from coastal environments, suggesting alternate lipid synthesis is a specific adaptation to phosphate scarcity. Similar gene clusters are found in the genomes of other marine alpha-proteobacteria, implying lipid renovation is a common strategy used by heterotrophic cells to reduce their requirement for phosphorus in oligotrophic habitats.