Biofilm is prevalent in various ecological niches, in which microbial cells interconnect with each other through extracellular polymeric substances including polysaccharides, extracellular DNA, and proteins. When living in biofilms, the microbial cells employ small signalling chemicals as their "language" to communicate mutually, and exhibit remarkable differences in physiology compared to those living in planktonic state. It has been proven that the development of biofilm is subject to the regulation of c-di-GMP, an important second messenger found in prokaryotes. Given its important roles of biofilms in microbial infection, industry application, plant-microbe interactions and environmental pollustion, biofilm is one of frontier research areas in microbiology. This special issue of "Biofilm and c-di-GMP" systematically reviews the current progresses in the multiple research frontiers, including biotechnology, infectious diseases, environmental microbiology and plant pathology, with special focus on the methods and techniques in biofilm research. We hope that the issue will boost the interest of students and young scientists in this exciting area of microbiology.
生物被膜 (Biofilm) 是微生物生存的主要形式。它是一种或多种微生物通过胞外多糖、胞外DNA、蛋白质等组成的基质聚集在一起形成的细胞多聚体。生物被膜中的微生物细胞之间存在密切的信号通讯，并且表现出与浮游生活时完全不同的生理代谢特征，其发育过程受到环二鸟苷单磷酸 (c-di-GMP) 等细胞第二信使的控制。由于生物被膜在基础生命科学和医疗、工业、农业、环境治理等应用科学中的重要性，相关研究是微生物学领域的前沿之一。本期专刊从生物工程、研究技术、感染与免疫、环境生物学和植物病理学等角度，较系统地对生物被膜的形成机制、调控分子机理、理化特性和应用技术等进行了综述或研究，展示了我国在本领域的研究水平，同时也对本领域未来发展趋势进行了有益的讨论。.
Keywords: biofilm; c-di-GMP; new technology; regulatory mechanism.