Genetic control of bacterial biofilms

Abstract

Nearly all bacterial species, including pathogens, have the ability to form biofilms. Biofilms are defined as structured ecosystems in which microbes are attached to surfaces and embedded in a matrix composed of polysaccharides, eDNA, and proteins, and their development is a multistep process. Bacterial biofilms constitute a large medical problem due to their extremely high resistance to various types of therapeutics, including conventional antibiotics. Several environmental and genetic signals control every step of biofilm development and dispersal. From among the latter, quorum sensing, cyclic diguanosine-5’-monophosphate, and small RNAs are considered as the main regulators. The present review describes the control role of these three regulators in the life cycles of biofilms built by Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella enterica serovar Typhimurium, and Vibrio cholerae. The interconnections between their activities are shown. Compounds and strategies which target the activity of these regulators, mainly quorum sensing inhibitors, and their potential role in therapy are also assessed.

Extracellular DNA in natural environments: features, relevance and applications

“…Similarly, several genes associated with the release of exDNA or with autolysis as well as quorum sensing inhibitors can be the target of an anti-biofilm therapy (e.g. Bao et al 2015; Beltrame et al 2015; Si et al 2015; reviewed by Wolska et al 2016). A nanomaterial cleaving exDNA of S. aureus biofilms was also proposed as a promising therapeutic material against biofilms (Thiyagarajan et al 2016).…”

“…The importance and the functions of exDNA in the formation of biofilms of pathogenic and environmental microorganisms (reviewed by Montanaro et al 2011 and Wnorowska et al 2015 (exDNA), Hobley et al 2015 (biofilms in general), Wolska et al 2016 (genetic control), Payne and Boles 2016 (matrix interactions and resulting implications) and Azeredo et al 2017 (methods)).…”

Biofilm dispersal: multiple elaborate strategies for dissemination of bacteria with unique properties

“…HapR is a transcription factor that indirectly represses the expression of the exopolysaccharide biosynthesis operon and alters the intracellular levels of c-di-GMP. At high cell density, the binding of autoinducers to their cognate receptors causes a cessation in the transcription of Qrr1-4, and thus promotes biofilm dispersal (Chambers and Sauer, 2013;Mart ınez and Vadyvaloo, 2014;Solano et al, 2014;Wolska et al, 2016).…”

Electroenhanced Antimicrobial Coating Based on Conjugated Polymers with Covalently Coupled Silver Nanoparticles Prevents Staphylococcus aureus Biofilm Formation

“…This includes several types of fimbriae, secreted substances such as SiiE (Salmonella intestinal infection E) and BapA (biofilm associated protein A) adhesins and structures with alternative functions like flagella [54][55][56]. S. Typhimurium biofilm matrix is mainly constituted of proteins such as curli fimbriae (encoded by the csg operons), the BapA protein, flagella and extracellular polysaccharides such as cellulose, colanic acid and the O-antigen capsule [54,[57][58][59][60].…”

“…adrA positively regulates cellulose synthesis through the production of the secondary messenger (3'-5')-cyclic diguanosine monophosphate (c-di-GMP), which acts as an activator of the cellulose synthase BcsA [58]. In addition, c-di-GMP can also directly control biofilm growth through other mechanisms, such as curli synthesis through activation of csgD expression, and inhibition of motility [57][58][59]. CsgD was also found to induce expression of BapA and the O-antigen capsule on Salmonella enterica serovar Enteritidis [58].…”