Bacteria have the ability to adapt to changing environments through rapid evolution mediated by modification of existing genetic information, as well as by horizontal gene transfer (HGT). This makes bacteria a highly successful life form when it comes to survival. Unfortunately, this genetic plasticity may result in emergence and dissemination of antimicrobial resistance and virulence genes, and even the creation of multiresistant “superbugs” which may pose serious threats to public health. As bacteria commonly reside in biofilms, there has been an increased interest in studying these phenomena within biofilms in recent years. This review summarizes the present knowledge within this important area of research.

Studies on bacterial evolution in biofilms have shown that mature biofilms develop into diverse communities over time. There is growing evidence that the biofilm lifestyle may be more mutagenic than planktonic growth. Furthermore, all three main mechanisms for HGT have been observed in biofilms. This has been shown to occur both within and between bacterial species, and higher transfer rates in biofilms than in planktonic cultures were detected. Of special concern are the observations that mutants with increased antibiotic resistance occur at higher frequency in biofilms than in planktonic cultures even in the absence of antibiotic exposure. Likewise, efficient dissemination of antimicrobial resistance genes, as well as virulence genes, has been observed within the biofilm environment. This new knowledge emphasizes the importance of biofilm awareness and control.

细菌具有通过修改现有遗传信息以及通过水平基因转移（HGT）介导的快速进化来适应不断变化的环境的能力。就生存而言，这使细菌成为非常成功的生命形式。不幸的是，这种遗传可塑性可能导致抗菌素耐药性和毒力基因的出现和传播，甚至导致产生多重耐药性的“超级细菌”，这可能对公共卫生构成严重威胁。由于细菌通常存在于生物膜中，因此近年来对研究生物膜中这些现象的兴趣日益浓厚。这篇综述总结了这一重要研究领域中的当前知识。

关于生物膜中细菌进化的研究表明，成熟的生物膜会随着时间的流逝而发展成各种群落。越来越多的证据表明，生物膜的生活方式可能比浮游生物更具诱变性。此外，已经在生物膜中观察到了HGT的所有三个主要机制。已经证明这在细菌种类之内和之间都发生，并且检测到生物膜中的转移率高于浮游培养物中的转移率。特别令人关注的是观察到，即使在没有抗生素暴露的情况下，具有增强抗药性的突变体在生物膜中的发生频率也比浮游培养中的频率高。同样，已经在生物膜环境中观察到了抗微生物抗性基因以及毒力基因的有效传播。