A long time has passed since regularly interspaced DNA repeats were discovered in prokaryotes. Today, those enigmatic repetitive elements termed clustered regularly interspaced short palindromic repeats (CRISPR) are acknowledged as an emblematic part of multicomponent CRISPR-Cas (CRISPR associated) systems. These systems are involved in a variety of roles in bacteria and archaea, notably, that of conferring protection against transmissible genetic elements through an adaptive immune-like response. This review summarises the present knowledge on the diversity, molecular mechanisms and biology of CRISPR-Cas. We pay special attention to the most recent findings related to the determinants and consequences of CRISPR-Cas activity. Research on the basic features of these systems illustrates how instrumental the study of prokaryotes is for understanding biology in general, ultimately providing valuable tools for diverse fields and fuelling research beyond the mainstream.

自从在原核生物中发现规则间隔的 DNA 重复序列以来，已经过去了很长时间。今天，那些被称为成簇规则间隔短回文重复序列 (CRISPR) 的神秘重复元素被认为是多组分 CRISPR-Cas（CRISPR 相关）系统的标志性部分。这些系统在细菌和古细菌中具有多种作用，尤其是通过适应性免疫样反应提供针对可传播遗传元件的保护。本综述总结了目前关于 CRISPR-Cas 的多样性、分子机制和生物学的知识。我们特别关注与 CRISPR-Cas 活动的决定因素和后果相关的最新发现。