活化（Competence）又称为胜任，是一个在微生物学、遗传学、分子生物学和细胞生物学里很常见的名词，用来指一种能令细胞有能力从细胞以外的环境接纳DNA的方法。无论是在自然条件下发生，或者在实验室中借由人造，一个细菌细胞的基因有指定的能力可以胜任外来之DNA。本文主要涉及在细菌中自然胜任的能力。被活化了的细胞一般被称为胜任细胞（Competent cell）。

令细胞活化，可以从自然活化及诱导活化两方面入手：

In microbiology, genetics, cell biology, and molecular biology, competence is the ability of a cell to take up extracellular ("naked") DNA from its environment. Competence may be differentiated between natural competence, a genetically specified ability of bacteria which is thought to occur under natural conditions as well as in the laboratory, and induced or artificial competence, which arises when cells in laboratory cultures are treated to make them transiently permeable to DNA. This article primarily deals with natural competence in bacteria, although information about artificial competence is also provided.