Institut Mittag-Leffler, Auravägen 17, Djursholm, 18260, Sweden.
Biol Direct. 2020 Oct 6;15(1):15. doi: 10.1186/s13062-020-00269-0.
The ability to self-sustain is one of the essential properties of life. However, a consistent and satisfying definition of self-sustainability is still missing. Currently, self-sustainability refers to either "no-intervention by a higher entity" or "regeneration of all the system's components". How to connect self-sustainability with heredity, another essential of life, is another problem, as they are often considered to be independent of each other. Last but not least, current definitions of self-sustainability failed to provide a practical method to empirically discern whether a chemical system is self-sustaining or not.
Here I propose a definition of self-sustainability. It takes into account the chemical reaction network itself and the external environment which is simplified as a continuous-flow stirred tank reactor. One distinct property of self-sustaining systems is that the system can only proceed if molecular triggers (or called, seeds) are present initially. The molecular triggers are able to establish the whole system, indicating that they carry the preliminary heredity of the system. Consequently, life and a large group of fires (and other dissipative systems) can be distinguished. Besides, the general properties and various real-life examples of self-sustaining systems discussed here together indicate that self-sustaining systems are not uncommon.
The definition I proposed here naturally connects self-sustainability with heredity. As this definition involves the continuous-flow stirred tank reactor, it gives a simple way to empirically test whether a system is self-sustaining or not. Moreover, the general properties and various real-life examples of self-sustaining systems discussed here provide practical guidance on how to construct and detect such systems in real biology and chemistry.
This article was reviewed by Wentao Ma and David Baum.
自我维持能力是生命的基本属性之一。然而，目前仍然缺乏一个一致且令人满意的自我可持续性定义。目前，自我可持续性是指“不受更高实体的干预”或“系统所有组件的再生”。如何将自我可持续性与遗传联系起来，这是另一个问题，因为它们通常被认为是相互独立的。最后但同样重要的是，当前自我可持续性的定义未能提供一种实用方法来从经验上辨别一个化学系统是否具有自我维持能力。
在这里，我提出了自我可持续性的定义。它考虑了化学反应网络本身和外部环境，外部环境简化为连续搅拌釜式反应器。自我维持系统的一个明显特征是，如果最初不存在分子触发物（或称为种子），系统就无法进行。分子触发物能够建立整个系统，这表明它们携带系统的初步遗传信息。因此，可以将生命和一大群火（和其他耗散系统）区分开来。此外，这里讨论的自我维持系统的一般性质和各种实际例子表明，自我维持系统并不罕见。
我在这里提出的定义自然地将自我可持续性与遗传联系起来。由于这个定义涉及连续搅拌釜式反应器，它提供了一种简单的方法来从经验上测试一个系统是否具有自我维持能力。此外，这里讨论的自我维持系统的一般性质和各种实际例子为如何在实际生物学和化学中构建和检测此类系统提供了实用指导。
本文由万涛和大卫·鲍姆审稿。
