Biofilm matrix

About: Biofilm matrix is a research topic. Over the lifetime, 1589 publications have been published within this topic receiving 110140 citations.

In situ Characterization of Biofilm Exopolymers Involved in the Accumulation of Chlorinated Organics

Abstract: The chemical nature and spatial arrangements of exopolymers in a degradative biofilm community were studied using a panel of fluorescein isothiocyanate– and tetramethyl rhodamine isothiocyanate–conjugated probes. Image analysis and dual channel imaging, in conjunction with scanning confocal laser microscopy, allowed detection and quantification of lectin binding to a variety of glycoconjugates. Relative abundance of these components varied between 0 and 67% of biofilm area at any depth. Lectin binding sites were distributed nonuniformly, both horizontally and vertically, within the >30-μm thick biofilms when the herbicide diclofop methyl was provided as the sole carbon source. A more uniform distribution of lectin binding sites was formed by the same biofilm community, when grown on a labile medium. Diclofop and its metabolites accumulated in extracellular polymers when biofilms were grown with diclofop as the sole source of carbon and energy, but not in the presence of the labile carbon source. There was a nearly 1:1 correspondence between the distribution of regions that accumulated diclofop (and other chlorinated ring compounds) and regions with binding sites for the α-l-fucose-specific Ulex europaeus Type I lectin. These regions also bound polyanionic and cationic fluor-conjugated dextrans, and a hydrophobic-specific dye, demonstrating the nonuniform distribution of charged and hydrophobic regions in the biofilm matrix. Hydrolytic enzymes, some of them selected for their specificity against residues identified by the lectin assay, had no effect on either structural integrity or diclofop binding. The distribution of diclofop binding, lectin binding, and charged regions observed in these biofilms indicated a degree of spatial organization and differentiation within the biofilm community. In addition, based on cell morphology and fluorescent gram reaction, these regions were primarily associated with one community member, a Bacillus coagulans strain.

The exopolysaccharide Psl-eDNA interaction enables the formation of a biofilm skeleton in Pseudomonas aeruginosa.

Abstract: Summary A hallmark of bacterial biofilms is a self-produced extracellular matrix of exopolysaccharide, extracellular DNA (eDNA) and proteins that hold bacterial cells together in the community. However, interactions among matrix components and how the interactions contribute to the formation of matrix remain unclear. Here, we show the physical interaction between exopolysaccharide Psl and eDNA, the two key biofilm matrix components of the opportunistic pathogen Pseudomonas aeruginosa. The interaction allows the two components to combine to form a web of eDNA–Psl fibres, which resembles a biofilm skeleton in the centre of pellicles to give bacteria structural support and capability against agents targeted on one matrix component. The web of eDNA–Psl fibres was also found in flow-cell biofilms at microcolonies initiation stage. The colocalization of eDNA or Psl fibres with bacterial cell membrane stain suggests that fibre-like eDNA is likely derived from the lysis of dead bacteria in biofilms. Psl can interact with DNA from diverse sources, suggesting that P. aeruginosa has the ability to use DNA of other organisms (such as human neutrophils and other bacterial species) to form its own communities, which might increase the survival of P. aeruginosa in multispecies biofilms or within a human host.

Role of a Putative Polysaccharide Locus in Bordetella Biofilm Development

Abstract: Bordetellae are gram-negative bacteria that colonize the respiratory tracts of animals and humans. We and others have recently shown that these bacteria are capable of living as sessile communities known as biofilms on a number of abiotic surfaces. During the biofilm mode of existence, bacteria produce one or more extracellular polymeric substances that function, in part, to hold the cells together and to a surface. There is little information on either the constituents of the biofilm matrix or the genetic basis of biofilm development by Bordetella spp. By utilizing immunoblot assays and by enzymatic hydrolysis using dispersin B (DspB), a glycosyl hydrolase that specifically cleaves the polysaccharide poly-β-1,6-N-acetyl-d-glucosamine (poly-β-1,6-GlcNAc), we provide evidence for the production of poly-β-1,6-GlcNAc by various Bordetella species (Bordetella bronchiseptica, B. pertussis, and B. parapertussis) and its role in their biofilm development. We have investigated the role of a Bordetella locus, here designated bpsABCD, in biofilm formation. The bps (Bordetella polysaccharide) locus is homologous to several bacterial loci that are required for the production of poly-β-1,6-GlcNAc and have been implicated in bacterial biofilm formation. By utilizing multiple microscopic techniques to analyze biofilm formation under both static and hydrodynamic conditions, we demonstrate that the bps locus, although not essential at the initial stages of biofilm formation, contributes to the stability and the maintenance of the complex architecture of Bordetella biofilms.

A Radio Frequency Electric Current Enhances Antibiotic Efficacy against Bacterial Biofilms

Abstract: Bacterial biofilms are notably resistant to antibiotic prophylaxis. The concentration of antibiotic necessary to significantly reduce the number of bacteria in the biofilm matrix can be several hundred times the MIC for the same bacteria in a planktonic phase. It has been observed that the addition of a weak continuous direct electric current to the liquid surrounding the biofilm can dramatically increase the efficacy of the antibiotic. This phenomenon, known as the bioelectric effect, has only been partially elucidated, and it is not certain that the electrical parameters are optimal. We confirm here the bioelectric effect for Escherichia coli biofilms treated with gentamicin and with oxytetracycline, and we report a new bioelectric effect with a radio frequency alternating electric current (10 MHz) instead of the usual direct current. None of the proposed explanations (transport of ions within the biofilm, production of additional biocides by electrolysis, etc.) of the direct current bioelectric effect are applicable to the radio frequency bioelectric effect. We suggest that this new phenomenon may be due to a specific action of the radio frequency electromagnetic field upon the polar parts of the molecules forming the biofilm matrix.

Nutrient dynamics and successional changes in a lentic freshwater biofilm

Abstract: SUMMARY 1. Colonisation, species composition, succession of microalgae and nutrient dynamics in biofilms grown under light and dark conditions were examined during the initial phases of biofilm development in a lentic freshwater environment. 2. Biofilms were developed on inert (perspex) panels under natural illuminated and experimental dark conditions and the panels were retrieved for analysis after different incubation periods. Analysed parameters included biofilm thickness, algal density, biomass, chlorophyll a, species composition, total bacterial density and nutrients such as nitrite, nitrate, phosphate and silicate. 3. Biofilm thickness, algal density, biomass, chlorophyll a and species richness were significantly higher in light-grown biofilms, compared with dark-grown biofilms. The light-grown biofilms showed a three-phased succession pattern, with an initial domination of Chlorophyceae followed by diatoms (Bacillariophyceae) and finally by cyanobacteria. Dark-grown biofilms were mostly dominated by diatoms. 4. Nutrients were invariably more concentrated in biofilms than in ambient water. Nutrient concentrations were generally higher in dark-grown biofilms except in the case of phosphate, which was more concentrated in light-grown biofilms. Significant correlations between nutrients and biofilm parameters were observed only in light-grown biofilms. 5. The N : P ratio in the biofilm matrix decreased sharply in the initial 4 days of biofilm growth; ensuing N-limitation status seemed to influence biofilm community structure. The N : P ratios showed significant positive correlations with the chlorophycean fraction in both light and dark-grown biofilms, and low N : P ratio in the older biofilms favoured cyanobacteria. Our data indicate that nutrient chemistry of biofilm matrix shapes community structure in microalgal biofilms.