Osmotrophy.
Osmotrophy.
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渗透压。
DOI：
10.1016/j.cub.2018.07.069
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Richards TA
中科院分区：
文献类型：
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作者：
Richards TA
什么是营养不良？渗透营养，正如这个词的第二部分所暗示的那样，描述了一种摄食机制，其中生物体使用渗透作用将可溶性“食物颗粒”或代谢物移动到细胞中以供利用。术语溶养用于描述一种特定和常见形式的溶养，其进一步涉及酶的分泌以分解细胞外环境中的大分子。这究竟是什么意思呢？简单地说，嗜热菌是一种有机体，它的“胃”在外面。它分泌酶到环境中，将大的聚合物如纤维素、木质素、脂质和蛋白质降解成简单的糖、脂肪酸和氨基酸，然后被它吸收。异养生物的成功取决于环境扩散速率和它们利用的营养物质的浓度梯度，以及膜渗透性和摄食细胞的表面积与体积比。然而，在自然界中，营养功能远没有这个术语所暗示的那么被动。许多营养型生物已经进化出细胞适应性来驱动它们的进食行为。这些包括释放代谢移动的亚基的强大分泌酶和促进快速有效摄取的高亲和力转运蛋白。因此，在天然生物系统中，营养需要胞外酶和同源质膜定位的转运蛋白的偶联部署。渗透营养是生物体多样性的一个特征，甚至人类胃肠道（包括内部胃）也表现出渗透营养，并含有一个渗透营养微生物群落。例如，人淀粉酶和麦芽糖酶被分泌到胃肠道的不同部分，以将膳食淀粉分解成其组成葡萄糖分子。反过来，这种葡萄糖被人类快速引导上皮细胞和复杂肠道微生物群的各种成员吸收。此外，肠道微生物生态系统在某种意义上，通过共同的营养功能，释放和利用一系列额外的碳水化合物。渗透营养在生物技术中也很重要。例如，某些酵母分泌的转化酶使它们能够分解植物产生的蔗糖，使葡萄糖和果糖能够让我们酿造葡萄酒和啤酒。
What is osmotrophy? Osmotrophy, as the second part of the word suggests, describes a feeding mechanism in which an organism uses osmosis for the purpose of moving soluble ‘food particles’ or metabolites into a cell to be utilised. The term lysotrophy is used to describe a specific and common form of osmotrophy that further involves the secretion of enzymes to break down macromolecules in the extracellular environment. What does this actually mean? Well simply, an osmotroph is an organism that has its ‘stomach’on the outside. It secretes enzymes into the environment that degrade large polymers—such as cellulose, lignin, lipids, and proteins—into simple sugars, fatty acids, and amino acids that it can then absorb. The success of osmotrophic organisms is determined by environmental diffusion rates and concentration gradients of the nutrients they utilize, as well as the membrane permeability and surface-to-volume ratio of the feeding cell. However, in nature, osmotrophic functions are much less passive than the term implies. Many osmotrophs have evolved cellular adaptations to drive their feeding behaviour. These include powerful secreted enzymes that liberate osmotically mobile subunits and highaffinity transporters that facilitate rapid and efficient uptake. In natural biological systems, osmotrophy therefore requires the coupled deployment of extracellular enzymes and cognate plasmamembrane-localised transport proteins. Osmotrophy is a feature of a very wide diversity of organisms—even the human gastrointestinal tract (including an internal stomach) demonstrates osmotrophy and harbours an osmotrophic microbial community. For example, the human amylase and maltase enzymes are secreted into different sections of the gastrointestinal tract to break down dietary starch into its constituent glucose molecules. In turn, this glucose is taken up by both humanQuick guide epithelial cells and various members of the complex gut microbiota. In addition, the gut microbioal ecosystem acts—in a sense, collectively, through osmotrophic function—to liberate and make use of a whole range of additional carbohydrates. Osmotrophy is also important in biotechnology. For instance, secretion of invertase by certain yeasts allows them to break down plant-generated sucrose, rendering the glucose and fructose that allow us to brew wine and beer.