Lee D H, Severin K, Yokobayashi Y, Ghadiri M R
Department of Chemistry, The Scripps Research Institute, La Jolla, California 92037, USA.
Nature. 1997 Dec 11;390(6660):591-4. doi: 10.1038/37569.
Symbiosis is an association between different organisms that leads to a reciprocal enhancement of their ability to survive. Similar mutually beneficial relationships can operate at the molecular level in the form of a hypercycle, a collective of two or more self-replicating species interlinked through a cyclic catalytic network. The superposition of cross-catalysis onto autocatalytic replication integrates the members of the hypercycle into a single system that reproduces through a second-order (or higher) form of nonlinear autocatalysis. The hypercycle population as a whole is therefore able to compete more efficiently for existing resources than any one member on its own. In addition, the effects of beneficial mutations of any one member are spread over the entire population. The formation of hypercycles has been suggested as an important step in the transition from inanimate to living chemistry, and a large number of hypercycles are expected to be embedded within the complex networks of living systems. But only one naturally occurring hypercycle has been well documented, while two autocatalytic chemical systems may contain vestiges of hypercyclic organization. Here we report a chemical system that constitutes a clear example of a minimal hypercyclic network, in which two otherwise competitive self-replicating peptides symbiotically catalyse each others' production.
共生是不同生物体之间的一种关联，这种关联会使它们的生存能力得到相互增强。类似的互利关系可以在分子层面以超循环的形式存在，超循环是由两个或更多通过循环催化网络相互连接的自我复制物种组成的集合。交叉催化叠加到自催化复制上，将超循环的成员整合到一个通过二阶（或更高阶）非线性自催化形式进行繁殖的单一系统中。因此，超循环群体作为一个整体，能够比任何一个单独的成员更有效地竞争现有资源。此外，任何一个成员的有益突变的影响会扩散到整个群体。超循环的形成被认为是从无生命化学向生命化学转变中的一个重要步骤，预计大量超循环会嵌入到生命系统的复杂网络中。但目前仅有一个自然存在的超循环得到了充分记录，而两个自催化化学系统可能包含超循环组织的痕迹。在此，我们报告一个化学系统，它构成了一个最小超循环网络的清晰例子，其中两个原本相互竞争的自我复制肽以共生方式催化彼此的产生。
