Biofilm

About: Biofilm is a research topic. Over the lifetime, 23010 publications have been published within this topic receiving 906812 citations. The topic is also known as: biofilms.

Extracellular DNA in soil and sediment: fate and ecological relevance.

Abstract: The review discusses origin, state and function of extracellular DNA in soils and sediments Extracellular DNA can be released from prokaryotic and eukaryotic cells and can be protected against nuclease degradation by its adsorption on soil colloids and sand particles Laboratory experiments have shown that DNA adsorbed by colloids and sand particles can be taken up by prokaryotic competent cells and be involved in natural transformation Most of these experiments have been carried out under artificial conditions with pure DNA molecules and pure adsorbing matrices, but in soils and sediments, pure surface-reactive colloids are not present and DNA is present with other cellular components (wall debris, proteins, lipids, RNA, etc) especially if released after cell lysis The presence of inorganic compounds and organic molecules on both soil particles and DNA molecules can influence the DNA adsorption, degradation and transformation of competent cells Extracellular DNA can be used as C, N and P sources by heterotrophic microorganisms and plays a significant role in bacterial biofilm formation The nucleotides and nucleosides originated from the degradation of extracellular DNA can be re-assimilated by soil microorganisms Extracellular DNA in soil can be leached and moved by water through the soil profile by capillarity In this way, the extracellular DNA secreted by a cell can reach a competent bacterial cell far from the donor cell Finally, the characterisation of extracellular DNA can integrate information on the composition of the microbial community of soil and sediments obtained by analysing intracellular DNA

Indole is an inter-species biofilm signal mediated by SdiA

Abstract: Background As a stationary phase signal, indole is secreted in large quantities into rich medium by Escherichia coli and has been shown to control several genes (e.g., astD, tnaB, gabT), multi-drug exporters, and the pathogenicity island of E. coli; however, its impact on biofilm formation has not been well-studied.

Tolerance to the antimicrobial peptide colistin in Pseudomonas aeruginosa biofilms is linked to metabolically active cells, and depends on the pmr and mexAB‐oprM genes

Abstract: Bacteria living as biofilm are frequently reported to exhibit inherent tolerance to antimicrobial compounds, and might therefore contribute to the persistence of infections. Antimicrobial peptides are attracting increasing interest as new potential antimicrobial therapeutics; however, little is known about potential mechanisms, which might contribute to resistance or tolerance development towards these compounds in biofilms. Here we provide evidence that a spatially distinct subpopulation of metabolically active cells in Pseudomonas aeruginosa biofilms is able to develop tolerance to the antimicrobial peptide colistin. On the contrary, biofilm cells exhibiting low metabolic activity were killed by colistin. We demonstrate that the subpopulation of metabolically active cells is able to adapt to colistin by inducing a specific adaptation mechanism mediated by the pmr operon, as well as an unspecific adaptation mechanism mediated by the mexAB-oprM genes. Mutants defective in either pmr-mediated lipopolysaccharide modification or in mexAB-oprM-mediated antimicrobial efflux were not able to develop a tolerant subpopulation in biofilms. In contrast to the observed pattern of colistin-mediated killing in biofilms, conventional antimicrobial compounds such as ciprofloxacin and tetracycline were found to specifically kill the subpopulation of metabolically active biofilm cells, whereas the subpopulation exhibiting low metabolic activity survived the treatment. Consequently, targeting the two physiologically distinct subpopulations by combined antimicrobial treatment with either ciprofloxacin and colistin or tetracycline and colistin almost completely eradicated all biofilm cells.

Pel is a cationic exopolysaccharide that cross-links extracellular DNA in the Pseudomonas aeruginosa biofilm matrix

Abstract: Biofilm formation is a complex, ordered process. In the opportunistic pathogen Pseudomonas aeruginosa, Psl and Pel exopolysaccharides and extracellular DNA (eDNA) serve as structural components of the biofilm matrix. Despite intensive study, Pel’s chemical structure and spatial localization within mature biofilms remain unknown. Using specialized carbohydrate chemical analyses, we unexpectedly found that Pel is a positively charged exopolysaccharide composed of partially acetylated 1→4 glycosidic linkages of N-acetylgalactosamine and N-acetylglucosamine. Guided by the knowledge of Pel’s sugar composition, we developed a tool for the direct visualization of Pel in biofilms by combining Pel-specific Wisteria floribunda lectin staining with confocal microscopy. The results indicate that Pel cross-links eDNA in the biofilm stalk via ionic interactions. Our data demonstrate that the cationic charge of Pel is distinct from that of other known P. aeruginosa exopolysaccharides and is instrumental in its ability to interact with other key biofilm matrix components.