Showing papers on "Biofilm matrix published in 2000"

Role of biofilms in antimicrobial resistance.

Abstract: Biofilms are formed by a spectrum of microorganisms, including pathogens, and provide a means for these organisms to protect themselves against antimicrobial agents. Several mechanisms have been proposed to explain this phenomenon of resistance within biofilms, including delayed penetration of the antimicrobial into the biofilm extracellular matrix, slowing of growth rate of organisms within the biofilm, or other physiologic changes brought about by interaction of the organisms with a surface. The practical implications of biofilm formation are that alternative control strategies must be devised both for testing the susceptibility of the organisms within the biofilm and treating the established biofilm to alter its structure. A number of testing protocols have been developed. Effective treatment strategies will incorporate antimicrobials or other agents that have been demonstrated to penetrate and kill biofilm organisms, or treatments that disrupt or target specific components of the biofilm matrix. A better understanding of the role of biofilms in infection and how in vivo biofilms respond to selected treatments requires more study.

Exopolymer Microdomains as a Structuring Agent for Heterogeneity Within Microbial Biofilms

Abstract: It is now well-recognized that the majority, and often most active fractions, of microbial cells in many natural systems occur as surface-associated biofilms. In sedimentary environments, biofilm formation represents an important functional adaptation for microbial life. At the level of an individual sediment particle, the biofilm community represents a cacophony of cellular and extracellular processes enclosed within an amorphous biofilm. Recent studies using new analytical approaches now suggest that the seemingly amorphous biofilm instead may be a highly structured system, one in which microbial cells actively manipulate their extracellular polymers and overall microenvironment to accomplish specific tasks. At microspatial scales (nanometers to micrometers), biofilm polymers are important in sequestering of nutrients, localization of extracellular enzymes, and providing a protective and stabilizing microenvironment for cells. Examination of the three-dimensional nature of microbial biofilm communities and activities through the use of nuclear magnetic resonance (NMR) spectroscopy, confocal laser microscopy (CLM), atomic-force microscopy (AFM) and other techniques are beginning to provide quantitative evidence for microscale partitioning within biofilms. In light of these new data, the biofilm is explored here as an important structural matrix to partition microbial extracellular activities and effectively promote heterogeneity over very small (i.e., molecular) spatial scales. Structuring and partitioning may occur through the formation of “exopolymer-mediated microdomains.” These are regions of a biofilm matrix where specific types of exopolymers are concentrated and impart unique physical/chemical properties to the biofilm. Accumulating evidence, derived from isotope sorption studies, electron microscopy, and CLM supports this idea. The presence of exopolymer microdomains may provide microorganisms with a structuring mechanism to spatially segregate extracellular activities over small spatial scales.

Cohesiveness in biofilm matrix polymers.

Abstract: A review with 60 refs. Topics discussed include microbial aggregates, the role of extracellular polymeric substances (EPS) as microbial aggregate construction material, the cohesiveness of matrix polymers, and the role of EPS in microbial aggregation.

Evaluation of Fluorescently Labeled Lectins for Noninvasive Localization of Extracellular Polymeric Substances in Sphingomonas Biofilms

Abstract: Three strains of Sphingomonas were grown as biofilms and tested for binding of five fluorescently labeled lectins (Con A-type IV-TRITC or -Cy5, Pha-E-TRITC, PNA-TRITC, UEA 1-TRITC, and WGA-Texas red). Only ConA and WGA were significantly bound by the biofilms. Binding of the five lectins to artificial biofilms made of the commercially available Sphingomonas extracellular polysaccharides was similar to binding to living biofilms. Staining of the living and artificial biofilms by ConA might be explained as binding of the lectin to the terminal mannosyl and terminal glucosyl residues in the polysaccharides secreted by Sphingomonas as well as to the terminal mannosyl residue in glycosphingolipids. Staining of the biofilms by WGA could only be explained as binding to the Sphingomonas glycosphingolipid membrane, binding to the cell wall, or nonspecific binding. Glycoconjugation of ConA and WGA with the target sugars glucose and N-acetylglucosamine, respectively, was used as a method for evaluation of the specificity of the lectins towards Sphingomonas biofilms and Sphingomonas polysaccharides. Our results show that the binding of lectins to biofilms does not necessarily prove the presence of specific target sugars in the extracellular polymeric substances (EPS) in biofilms. The lectins may bind to non-EPS targets or adhere nonspecifically to components of the biofilm matrix.

Herbivory in an acid stream

Abstract: SUMMARY 1. Spatial and temporal variation in the distribution and feeding of non-predatory macroinvertebrates was investigated in a first-order, acid stream in the Ashdown Forest, southern England. 2. Stonefly (Nemouridae) and chironomid (Orthocladiinae) larvae were abundant on the upper surfaces of mineral substrata of three sizes (small stones, large stones, bedrock). The density of larvae in each taxonomic group did not vary among substrata of different sizes, although strong seasonal variation existed. 3. Nemourids and chironomids (H. marcidus) collected from the upper surfaces of substrata exhibited generalist feeding habits, consuming algae (diatoms, coccoid and filamentous green algae), detritus (biofilm matrix material and fine particulate organic matter (FPOM)) and inorganic debris. 4. There was spatial variation in the gut contents of nemourids. The proportion of algae in the guts of larvae often increased with the size of the substratum from which they were collected. Strong temporal variation in the composition of the diet also existed. Nemourids ingested a large quantity of attached algae and biofilm matrix from the biofilm in spring and winter, but consumed loose FPOM and associated microflora in summer and autumn. 5. We conclude that, in this acid stream, the trophic linkage between algae and grazers is maintained by ‘detritivorous’ stonefly and chironomid species. The relationship between the feeding habits of these larvae and other life-history attributes, such as mouthpart morphology and mobility, is discussed.

Artificial biofilm model – a useful tool for biofilm research

Abstract: For biofilm studies, artificial models can be very helpful in studying processes in hydrogels of defined composition and structure. Two different types of artificial biofilm models were developed. Homogeneous agarose beads (50–500 μm diameter) and porous beads (260 μm mean diameter) containing pores with diameters from 10 to 80 μm (28 μm on average) allowed the embedding of cells, particles and typical biofilm matrix components such as proteins and polysaccharides. The characterisation of the matrix structures and of the distribution of microorganisms was performed by confocal laser scanning microscopy. The physiological condition of the embedded bacteria was examined by redox activity (CTC-assay) and membrane integrity (Molecular Probes LIVE/DEAD-Kit). Approximately 35% of the immobilised cells (Pseudomonas aeruginosa SG81) were damaged due to the elevated temperature required for the embedding process. It was shown that the surviving cells were able to multiply when provided with nutrients. In the case of homogeneous agarose beads, cell growth only occurred near the bead surface, while substrate limitation prevented growth of more deeply embedded cells. In the porous hydrogel, cell division was observed across the entire matrix due to better mass transport. It could be shown that embedding in the artificial gel matrix provided protection of immobilized cells against toxic substances such as sodium hypochlorite (0.5 mg/l, 30 min) in comparison to suspended cells, as observed in other immobilized systems. Thus, the model is suited to simulate important biofilm matrix properties.

Podostemaceae Depend on Sticky Biofilms with Respect to Attachment to Rocks in Waterfalls

Abstract: Investigations of the method by which the plant body of Podostemaceae fastens to naked rocks in waterfalls refute the hitherto accepted existence of a special glue secreted by these plants. Instead, roots and crusts of Podostemaceae utilize bacteria, mainly cyanobacteria of biofilms, for attachment. These plants essentially depend on the sticky components (extracellular polymeric substances [EPS]) of slime‐coated cyanobacteria that live within biofilms covering the rocky substratum: the EPS of biofilm functions as the pasting agent. Adhesive hairs, developing from the lower side of the Podostemonad plant body, stick to the cyanobacteria threads and the biofilm matrix, which, in turn, fasten to the substratum. This mode, occurring widely, is exemplified herein with five Old World species of both subfamilies of Podostemaceae.

Disinfection of dental unit waterlines with an oral antiseptic.

Abstract: The problem of potential pathogens in biofilm within dental unit waterlines is real. Even though some chemical agents can disinfect biofilms, there remains concern that all remnants of the biofilm matrix are not eliminated, even with periodic treatments, and the bacterial populations in dental unit waterlines recur rapidly. Toxic and caustic residual chemicals are also a concern. In multiple trials following overnight treatment of dental unit waterlines with Listerine Antiseptic (LA), recurrence was investigated by evaluating effluent and biofilm specimens by plate culture. The presence or absence of biofilm within the dental unit waterlines was evaluated, pre- and post-treatment, by scanning electron microscopy. Baseline evaluations of dental unit waterlines determined the effluent and biofilm to harbor an average of 1 x 10(5) CFU per ml and 1 x 10(4) CFU per cm2, respectively, prior to treatment. Overnight, 18-hour treatment with LA rendered effluent and biofilm samples free of recoverable bacteria in all cases immediately following treatment. Viable bacteria in the effluent of treated dental unit waterlines recurred to near pre-treatment levels by Day 7. The minimum inhibitory concentrations for each of the recovered isolates did not change following overnight treatment. Repeated overnight treatments at the beginning of a one-week study were effective in inhibiting recurrence of viable bacteria in the biofilm and effluent indefinitely, but still failed to completely remove the biofilm matrix. New tubing treated prior to use and then daily with LA did not develop a detectable biofilm by scanning electron microscopy during the study. One-month long follow-up clinical trials have demonstrated that a maintenance solution of a 1:50 concentration of LA and sterile distilled water in self-contained dental units with new tubing is effective for prolonged periods in maintaining the effluent within the American Dental Association's recommendation for the year 2000 of < 200 CFU per ml. The clinical significance of these findings is that a solution to the problem of dental unit waterline contamination may be currently available. Since antimicrobial LA is safe for patient use, it may be one of the most viable options suggested to date.

Metabolic Indicators for Assessing Bacterial Viability in Hygiene Sampling Using Cells in Suspension and Swabbed Biofilm

Abstract: In the present study various combinations of metabolic indicators were used in viability studies of foodborne spoilage and pathogenic organisms. Various metabolic stains were tested in pure culture suspensions of Pseudomonas fragi and Listeria monocytogenes containing only viable cells, both viable and dead cells or only dead cells. In addition, foodborne monospecies biofilms of L. monocytogenes and P. fragi were studied. The biofilms were grown on stainless steel (AISI 304, 2B) surfaces. The results showed that both the LIVE/DEAD Bac Light Viability Kit (LIVE/DEAD) and the 5-cyano-2,3-ditolyl tetrazolium chloride (CTC)-4′,6-diamidino-2-phenylindole (DAPI) staining procedures offer a rapid, easy and reliable method for metabolic investigation of bacteria in suspension and swabbed biofilm bacteria. Assessment of replicate samples using luciferin–luciferase-based ATP measurement and conventional cultivation corroborated the results of swabbed biofilm bacteria obtained by staining. LIVE/DEAD staining cannot be used for direct staining of biofilms on surfaces, due to interference between the stain and polysaccharides of the biofilm matrix and slime. Staining by CTC-DAPI is suitable for studying viability of cells both in suspension and in biofilms attached to surfaces. The other staining procedures tested were not satisfactory or only slightly satisfactory in distinguishing between viable and dead cells.

Monitoring the Organization of Microbial Biofilm Communities

Abstract: Microbial organization within a biofilm community can be thought of as the product of species composition and spatial positioning of individuals within the biofilm matrix. Species composition within a microbial community, also referred to as community structure,8 determines the community’s overall genetic potential for survival and reproductive success under various environmental conditions. Spatial positioning allows individuals to interact physiologically and genetically. It also allows the creation of favorable microbial microenvironments within hostile macroenvironments. When a biofilm community is subjected to an environmental perturbation (e.g., an introduction of a pollutant or antimicrobial compound), continued reproductive success may be facilitated by a process of reorganization consisting of changes in composition and spatial arrangement of individuals within the community. Thus, the structural and spatial organization of a biofilm community, and its functional significance, should be a consideration when attempting to control or enhance the activities of biofilm communities in industrial or environmental settings.

Community structure and co-operation in biofilms : Fifty-ninth Symposium of the Society for General Microbiology held at The University of Exeter, September 2000

Abstract: List of contributors Preface 1. An overview of biofilms as functional communities J. Wimpenny 2. Initial microbial adhesion events: mechanisms and implications H. J. Busscher and H. C. van der Mei 3. Physiological events in biofilm formation D. G. Davies 4. Environmental and genetic factors influencing biofilm structure P. Stoodley, L. Hall-Stoodley, J. D. Boyle, F. Jorgensen and H. M. Lappin-Scott 5. Coaggregation and coadhesion in oral biofilms P. E. Kolenbrander, R. N. Andersen, K. M. Kazmerzak and R. J. Palmer, Jr 6. Cohesiveness in biofilm matrix polymers H.-C. Flemming, J. Wingender, C. Mayer, V. Koerstgens and W. Borchard 7. Microbial detachment from biofilms G. F. Moore, B. C. Dunsmore, S. M. Jones, C. W. Smejkal, J. Jass, P. Stoodley and H. M. Lappin-Scott 8. Modelling and predicting biofilm structure C. Picioreanu, M. C. M. van Loosdrecht and J. J. Heijnen 9. Microbial community interactions in biofilms P. D. Marsh and G. H. W. Bowden 10. Microbial communities: aggregates of individuals or co-ordinated systems S. Molin, J. A. J. Haagensen, K. B. Barken and C. Sternberg 11. Gene transfer in biofilms L. J. Ehlers 12. Population dynamics in microbial biofilms A. J. McBain, D. G. Allison and P. Gilbert 13. Biodegradation by biofilm communities G. M. Wolfaardt, D. R. Korber, S. Karthikeyan and D. E. Caldwell 14. Biofilms and prosthetic devices R. Bayston 15. Biofilms: problems of control D. G. Allison, A. J. McBain and P. Gilbert 16. Biofilms in the New Millennium: musings from a peak in Xanadu J. W. Costerton Index.