Protein secretion is important for many biotic and abiotic interactions. The evolution of protein secretion systems of bacteria, and related nanomachines, occurred by the co-option of machineries for motility, conjugation, injection, or adhesion. Some of these secretion systems emerged many times, whereas others are unique. In most cases, their evolution occurred by successive rounds of gene accretion, deletion, and horizontal transfer, resulting in machines that can be very different from the original ones. The frequency with which such co-option processes occurred seems to depend on the complexity of the systems, their differences to the ancestral machines, the availability of genetic material to tinker with, and possibly on the mechanisms of effector recognition. Understanding the evolution of secretion systems illuminates their functional diversification and could drive the discovery of novel systems.

蛋白质分泌对于许多生物和非生物相互作用都很重要。细菌和相关纳米机器的蛋白质分泌系统的进化是通过共同选择动力，结合，注射或粘附机制而发生的。这些分泌系统中的一些出现了很多次，而另一些则是独特的。在大多数情况下，它们的进化是通过连续几轮的基因吸收，缺失和水平转移而发生的，从而导致机器可能与原始机器大不相同。这种共同选择过程发生的频率似乎取决于系统的复杂性，它们与祖先机器的差异，遗传材料的修补可能性以及可能的效应子识别机制。