SAR11 bacteria have a high affinity and multifunctional glycine betaine transporter
SAR11 bacteria have a high affinity and multifunctional glycine betaine transporter
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DOI：
10.1111/1462-2920.14649
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发表时间：
2019-07-01
影响因子：
5.1
通讯作者：
Giovannoni, Stephen J.
中科院分区：
文献类型：
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作者：
Noell, Stephen E.;Giovannoni, Stephen J.
海洋浮游细菌面临着对有限营养资源的激烈竞争。SAR 11是一个普遍存在的非常小且高度丰富的α-变形菌分支，已知其将大部分能量用于合成结合底物的ATP结合盒周质蛋白。我们推测，它们的小尺寸和相对较大的周质空间可能使它们能够胜过其他浮游细菌的营养物质。通过对C-14-甘氨酸甜菜碱的吸收实验，发现两株SAR 11菌株，Speridatus Pelagibacter sp.HTCC7211和Cand. P. ubique HTCC 1062对甜菜碱（GBT）具有极高的亲和力，半饱和（K-s）值约为1 nM，比亲和力值在8至14 L mg细胞（-1）h（-1）之间。竞争抑制研究表明，GBT转运蛋白在这些菌株是多功能的，除了GBT运输多种底物。两株菌都能利用大部分转运化合物进行代谢和ATP的产生。我们的研究结果表明，Pelagibacter细胞主要负责在海水中观察到的高亲和力和多功能GBT摄取系统。全细胞亲和力的最大化可能使这些生物能够在异养浮游生物群落的总运输能力超过供应量，从而降低环境浓度的时期有效地竞争营养物质。
Marine bacterioplankton face stiff competition for limited nutrient resources. SAR11, a ubiquitous clade of very small and highly abundant Alphaproteobacteria, are known to devote much of their energy to synthesizing ATP-binding cassette periplasmic proteins that bind substrates. We hypothesized that their small size and relatively large periplasmic space might enable them to outcompete other bacterioplankton for nutrients. Using uptake experiments with C-14-glycine betaine, we discovered that two strains of SAR11, Candidatus Pelagibacter sp. HTCC7211 and Cand. P. ubique HTCC1062, have extraordinarily high affinity for glycine betaine (GBT), with half-saturation (K-s) values around 1 nM and specific affinity values between 8 and 14 L mg cell(-1) h(-1). Competitive inhibition studies indicated that the GBT transporters in these strains are multifunctional, transporting multiple substrates in addition to GBT. Both strains could use most of the transported compounds for metabolism and ATP production. Our findings indicate that Pelagibacter cells are primarily responsible for the high affinity and multifunctional GBT uptake systems observed in seawater. Maximization of whole-cell affinities may enable these organisms to compete effectively for nutrients during periods when the gross transport capacity of the heterotrophic plankton community exceeds the supply, depressing ambient concentrations.