Showing papers on "Biofilm matrix published in 1991"

Biofouling in Water Treatment

Abstract: Biofouling is understood as the unwanted deposition and growth of living organisms on surfaces. In water treatment, in almost all cases it is caused by microorganisms They can contaminate the water, cover and block surfaces, host pathogens, and attack their support. Biofouling is a biofilm problem. It is defined operationally and refers to that extent of biofilm growth which interferes with the demands of water production or consumption process. Control of biofouling requires effective detection. Water samples give no valuable information to localize biofilms or to assess their extent. Thus, surfaces have to be investigated. Simple field methods are presented as well as laboratory techniques to evaluate the presence of biofilms. Sanitization of biofouling has to include the removal of biofilms rather than the killing of all cells. Sanitization strategies usually have to break the physical stability of the biofilm matrix by chemicals and to remove the biofouling layer by shear forces. Prevention of biofouling depends on a “clean system philosophy”: clean equipment, raw water and chemicals, early detection of biofilm formation and early cleaning measures. In most systems, biofilm development can only be prevented with high expenditures. Thus, the extent of biofilm accumulation has to be kept below the level of interference. The extent of biofilm growth is the result of the balance between growth and detachment and it is dependent on the nutrient situation, the temperature and the shear forces. The control of the nutrient situation in the fluid phase can be much more effective than the control of the cell numbers in order to reduce biofilm thickness. For the extent of biofilm accumulation as well as for cleaning measures, the stability of the biofilm matrix is the crucial factor. It depends on the shear forces, the nutrient situation, stabilizing filaments and particles and destabilizing chemicals and internal processes. “Coexistence with biofilms” requires a continuous awareness and strategies similar to those with which some marine animals prevent microbial colonization on their surface.

Exoenzyme accumulation in epilithic biofilms

Abstract: Although exoenzyme accumulation is often proposed as an explanation for the high metabolic activity of biofilms, little is known about the abundance, distribution and turnover rates of exoenzymes within these communities. To assess accumulation, epilithic biofilm samples were collected from a fourth-order boreal river and homogenized. The resulting particles were fractionated by size and each fraction was assayed for nine exoenzyme activities, chlorophyll, and ATP. In general, carbohydrase activities were not correlated with microbial biomass indicators; the largest pool of activity was in the aqueous phase (< 0.2 µm). Phenol oxidase, peroxidase, and phosphatase activities were largely particle-bound and often correlated with microbial biomass distribution. It was concluded that the epilithic biofilm matrix was effective at accumulating carbohydrase activity and that this accumulation may partially account for the metabolic resistance of epilithic biofilms to dissolved organic matter fluctuations.

Bacterial surface adhesives and biofilm matrix polymers of marine and freshwater bacteria

Abstract: The initial adhesive polymers and biofilm matrix polymers of a mat colony phenotype of Pseudomonas sp. NCIMB2021 were investigated in situ using two optical techniques, interference reflection microscopy (IRM) and light section microscopy (LSM). Newly attached cells and bacterial biofilms were tested with various chemical treatments that might be expected to alter the integrity of specific intrapolymer or polymer‐substratum interactions, e.g. electrostatic, hydrophobic interactions, or hydrogen bonding, to determine whether the two types of adhesive polymer responded in the same way. A contraction or expansion of initial adhesive polymer was evaluated by IRM, whereas thickness changes in biofilms, dominated by matrix polymers, were measured by LSM. The test chemicals were solutions of Tween 20, ethylene glycol‐bis(p‐aminoethylether)N,N,N'N'‐tetraacetic acid (EGTA), ethylenediaminetetraacetic acid (EDTA), guanidine thiocyanate (GT), dimethyl sulphoxide (DMSO), all in an artificial seawater, 0–4 M NaCl, and...

Comparative rates of antibiotic action against Staphylococcus epidermidis biofilms.

Abstract: The relative resistance of S. epidermidis implant-associated infections to antibiotic therapy has been ascribed to a protective function of the gluelike biofilm matrix produced by strains of S. epidermidis in contact with artificial surfaces. Using a standardized S. epidermidis biofilm assay we determined the periods of exposure required by various antibiotics to produce cessation of biofilm metabolic activity. Rifampin has the superior rate of action, producing substantial disruption of biofilm activity by 7 hr of exposure, but leading to replacement of the susceptible bacterial cells by rifampin-resistant mutant survivors. Other antibiotics required longer periods of exposure, in excess of 48 hr, but produced a bactericidal outcome. Combinations of antibiotics with rifampin produced strikingly divergent results. Cefazolin and vancomycin (cell wall active antibiotics) produced a bactericidal outcome at 16 hr of exposure, whereas gentamicin (aminoglycoside) neutralized the rapid action of rifampin with metabolic activity maintained at 48 hr. We confirmed the selectively protective function of the S. epidermidis biofilm with regard to antibiotic action. In vitro biofilm assays may be of value in guiding antibiotic therapy in S. epidermidis implant-associated infection.