Gene Regulation in Biofilms

Dear Colleagues,

For a long time, bacteria have only been considered to live a planktonic lifestyle as floating or actively swimming single organisms. Over the past five decades, however, it has become increasingly clear that many bacteria can live in multicellular communities, e.g., through the formation of stress-resistant biofilms. Biofilm formation is a tightly regulated process found both in Gram-negative and Gram-positive bacteria that involves several steps: (i) attachment of planktonic bacteria to biotic or abiotic surfaces; (ii) microcolony formation through replication and cell-to-cell adhesion; (iii) development into highly organized mature biofilms embedded in an extracellular polymeric matrix; and (iv) dispersal of biofilm cells by switching to the planktonic state. In comparison with their planktonic counterparts, biofilm cells have been shown to have significantly better protection from the host immune response and up to 1000-fold less susceptibility to various antimicrobial agents due to their reduced metabolic rates, differential expression of efflux pumps, the presence of a self-produced extracellular polymeric matrix, and reduced uptake/increased sequestration of antimicrobial compounds. Hence, the ability of bacteria to form stress-resistant biofilms represents an exceptional adaption strategy for their survival in hostile environments, including human hosts. The biofilm lifestyle of many pathogens is currently recognized as the underlying cause for many difficult-to-treat persistent infections and represents a major challenge in hospital settings. To accomplish the exceptionally complex differentiation of planktonic bacteria into biofilm communities in a highly concerted fashion, bacteria employ numerous sophisticated regulatory mechanisms involving finely altered gene expression. A near-ubiquitous second messenger that coordinates diverse aspects of bacterial growth and behavior, including motility, virulence, and the transition of planktonic to biofilm lifestyle, is c-di-GMP. Elevated levels of c-di-GMP result in increased production of extracellular matrix components, adhesive pili, non-fimbrial adhesins, extracellular DNA, and other biofilm-associated characteristics such as impaired motility. Quorum sensing regulates cell density and induces changes in gene expression depending on the availability of signaling molecules and small non-coding RNAs. RNA-binding proteins, toxin-antitoxin systems, and riboswitches represent additional regulatory mechanisms that are known to be involved in biofilm regulation.

This Special Issue in Pathogens on “Gene Regulation in Biofilms” will focus on the latest state-of-art developments and current knowledge in the field of gene regulation in bacterial biofilms, both in vitro and in vivo. We invite authors to submit research or review manuscripts covering these important molecular aspects of biofilm regulation.

Prof. Dr. Jan-Ulrik Dahl
Guest Editor

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