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At least 73 records · Page 4Linked to original sources
PubMed2000

Artificial biofilm model--a useful tool for biofilm research.

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 microm diameter) and porous beads (260 microm mean diameter) containing pores with diameters from 10 to 80 microm (28 microm 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.

Biofilms↗
PubMed2004

Nutrient removal in a sequencing batch biofilm reactor (SBBR) using a vertically moving biofilm system.

In this paper, the performance of a sequencing batch biofilm reactor (SBBR) using an anoxic/anaerobic phase followed by an aerobic phase for nutrient removal from wastewater was investigated. In the laboratory SBBR unit, biofilm was grown on a plastic biofilm media module, which was vertically moved up into the air and down into the bulk fluid during the aerobic phase. The vertical movement of the biofilm module supplied oxygen to the microorganisms. The module was submerged in the wastewater during the anoxic/anaerobic phase. The percentage removals of total chemical oxygen demand (COD), total nitrogen (TN) and soluble orthophosphate (PO4-P) were 95.4%, 68.3% and 89.5% respectively at influent concentrations of COD 773 mg l(-1), TN 49.9 mg l(-1) and PO4-P 16.5 mg l(-1). The effluent COD was 35 mg l(-1), NH4-N 10.2 mg l(-1), NO3-N 5.5 mg l(-1), soluble PO4-P 1.7 mg l(-1) and suspended solids (SS) 19 mg l(-1).

Biofilms↗
PubMedDate not supplied

Immunology of Staphylococcal biofilm infections in the eye: new tools to study biofilm endophthalmitis.

Endophthalmitis is an important disease of the eye that is most frequently caused by postoperative and post-traumatic introduction of bacteria into the posterior segment of the eye. In the case of severe infections, visual acuity is greatly damaged or completely lost. Much work has focused on the ability of planktonic bacteria to cause infection and ocular damage while little work has focused on chronic infections in endophthalmitis mediated by the formation of bacterial biofilms on the surface of the lens. This review focuses on the interaction of Staphylococcus aureus and Staphylococcus epidermidis lens-associated biofilms in endophthalmitis. Additionally, this review highlights some relevant biofilm-immune system interactions and outlines a new in vivo mouse model to explore biofilm-related infections in endophthalmitis.

Animals↗
PubMed1997

The development of a small-scale biofilm model suitable for studying the effects of antibiotics on biofilms of gram-negative bacteria.

A method for the study of membrane-associated biofilm populations of Escherichia coli ATCC 8739 using modified Swinnex filter units was developed. Biofilms were established under carbon limitation in a chemically defined simple salts medium. Cells, pressure filtered on to cellulose nitrate membranes in situ, were perfused from the sterile side. Steady-state conditions were attained at which the growth rate of the sessile cells could be demonstrated to be proportional to the flow rate of medium. The antibiotic susceptibility of these biofilms was examined by including ciprofloxacin within the perfusing medium. Susceptibility of the biofilms to ciprofloxacin was found to be affected not only by its concentration, but also by the growth rate of the bacteria.

Anti-Infective Agents↗
PubMed2001

Salmonella enterica serovar typhimurium swarming mutants with altered biofilm-forming abilities: surfactin inhibits biofilm formation.

Swarming motility plays an important role in surface colonization by several flagellated bacteria. Swarmer cells are specially adapted to rapidly translocate over agar surfaces by virtue of their more numerous flagella, longer cell length, and encasement of slime. The external slime provides the milieu for motility and likely harbors swarming signals. We recently reported the isolation of swarming-defective transposon mutants of Salmonella enterica serovar Typhimurium, a large majority of which were defective in lipopolysaccharide (LPS) synthesis. Here, we have examined the biofilm-forming abilities of the swarming mutants using a microtiter plate assay. A whole spectrum of efficiencies were observed, with LPS mutants being generally more proficient than wild-type organisms in biofilm formation. Since we have postulated that O-antigen may serve a surfactant function during swarming, we tested the effect of the biosurfactant surfactin on biofilm formation. We report that surfactin inhibits biofilm formation of wild-type S. enterica grown either in polyvinyl chloride microtiter wells or in urethral catheters. Other bio- and chemical surfactants tested had similar effects.

Bacterial Proteins↗
PubMed2006

The membrane biofilm reactor: the natural partnership of membranes and biofilm.

Many exciting new technologies for water-quality control combine microbiological processes with adsorption, advanced oxidation, a membrane or an electrode to improve performance, address emerging contaminants or capture renewable energy. An excellent example is the H2-based membrane biofilm reactor (MBfR), which delivers H2 gas to a biofilm that naturally accumulates on the outer surface of a bubbleless membrane. Autotrophic bacteria in the biofilm oxidise the H2 and use the electrons to reduce NO3-, CIO4- and other oxidised contaminants. This natural partnership of membranes and biofilm makes it possible to gain many cost, performance and simplicity advantages from using H2 as the electron donor for microbially catalysed reductions. The MBfR has been demonstrated for denitrification in drinking water; reduction of perchlorate in groundwater; reduction of selenate, chromate, trichloroethene and other emerging contaminants; advanced N removal in wastewater treatment and autotrophic total-N removal.

Biofilms↗
PubMed2001

Contributions of biofilm versus suspended bacteria in an aerobic circulating-bed biofilm reactor.

This study demonstrated that, during the two-step biodegradation of toluene in an aerobic circulating-bed biofilm reactor, biofilm and suspended bacteria played critical roles. Although the suspended bacteria were less than 1% of the total amount of biomass in the system, they transformed up to 30% of the toluene into its intermediate in the bulk liquid phase. On the other hand, most of the toluene intermediate was removed inside the biofilm, where diffusion resistance reduced the toluene concentration, thereby relieving inhibition to the degradation reaction of the intermediate. The suspended bacteria are most important for rapidly biodegraded substrates, for which diffusion limitation controls the kinetics in the biofilm. They lose importance when the effects of an inhibiting substrate must be overcome.

Bacteria, Aerobic↗
PubMed2001

Effect of EPS on biofilm structure and function as revealed by an individual-based model of biofilm growth.

We have simulated a nitrifying biofilm with one ammonia and one nitrite oxidising species in order to elucidate the effect of various extracellular polymeric substance (EPS) production scenarios on biofilm structure and function. The individual-based model (IbM) BacSim simulates diffusion of all substrates on a two-dimensional lattice. Each bacterium is individually simulated as a sphere of given size in a continuous, three-dimensional space. EPS production kinetics was described by a growth rate dependent and an independent term (Leudeking-Piret equation). The structure of the biofilm was dramatically influenced by EPS production or capsule formation. EPS production decreased growth of producers and stimulated growth of non-producers because of the energy cost involved. For the same reason, EPS accumulation can fall as its rate of production increases. The patchiness and roughness of the biofilm decreased and the porosity increased due to EPS production. EPS density was maximal in the middle of the vertical profile. Introduction of binding forces between like cells increased clustering.

Ammonia↗
PubMed1992

Radiochemical assay to measure the biofilm produced by coagulase-negative staphylococci on solid surfaces and its use to quantitate the effects of various antibacterial compounds on the formation of the biofilm.

A firmly adherent mass of slime plus organisms (biofilm) accumulates on the sides of culture tubes when some strains of coagulase-negative staphylococci are grown in a chemically-defined medium containing [14C]glucose. This mass was washed (to remove labelled medium) and then counted after adding scintillation fluid. Organisms from the liquid culture were also washed and counted to check that [14C]glucose had been utilised to label the bacteria. Nine strains were examined in this way, and the results were compared with those obtained with four older techniques for recognising slime production or adherent bacteria. The new method is quick, and has advantages of reproducibility and good discrimination between strains; there was a 15-fold difference in counts in the biofilm between slime-producing and non-producing strains respectively. With the new radiolabel assay, the effects of several antibacterial compounds on the build-up of the biofilm were investigated with four slime-producing strains. Tunicamycin, chloramphenicol and 5-fluorouracil, at levels below their minimum growth-inhibitory concentrations, each greatly diminished biofilm formation; several other drugs had less effect.

Adenosine Triphosphate↗
PubMed2006

Sequencing batch membrane biofilm reactor for simultaneous nitrogen and phosphorus removal: novel application of membrane-aerated biofilm.

A sequencing batch membrane biofilm reactor (SBMBfR) was developed for simultaneous carbon, nitrogen, and phosphorus removal from wastewater. This reactor was composed of two functional parts: (1) a gas-permeable membrane on which a nitrifying biofilm formed and (2) a bulk solution in which bacteria, mainly denitrifying polyphosphate-accumulating organisms (DNPAOs), were suspended. The reactor was operated sequentially under anaerobic condition and then under membrane aeration condition in one cycle. During the anaerobic period, organic carbon was consumed by DNPAOs; this was accompanied by phosphate release. During the subsequent membrane aeration period, nitrifying bacteria utilized oxygen supplied directly to them from the inside of the membrane. Consequently, the nitrite and nitrate products diffused into the bulk solution, where they were used by DNPAOs as electron acceptors for phosphate uptake. In a long-term sequencing batch operation, the mean removal efficiencies of total organic carbon (TOC), total nitrogen (T-N), and total phosphorus (T-P) under steady-state condition were 99%, 96%, and 90%, respectively. In addition, fluorescence in situ hybridization (FISH) clearly demonstrated the difference in bacterial community structure between the membrane biofilm and the suspended sludge: ammonia-oxidizing bacteria belonging to the Nitrosomonas group were dominant in the region adjacent to the membrane throughout the operation, and the occupation ratio of the well-known polyphosphate-accumulating organism (PAO) Candidatus "Accumulibacter phosphates" in the suspended sludge gradually increased to a maximum of 37%.

Bacteria↗
PubMed2004

Biofilm and biomass characteristics in high-performance fluidized-bed biofilm reactors.

Two laboratory-scale fluidized-bed biofilm reactors (FBBRs) were used to investigate the biomass concentration and the biofilm characteristics in a high-performance FBBR used for the denitrification of exceptionally high-nitrate wastewater (1000 mg N/L). Reported correlations by other workers for predicting the biomass concentration in FBBR were examined for their validity in comparison with the experimental results of this study and the best set of applicable correlations was recommended. The effects of the two main operational parameters, the superficial velocity and nitrogen loading rate on the biomass concentration in the FBBR were also studied. Correlations for the drag coefficient and the expansion index from the literature, together with the biofilm dry density correlation produced from this study were found to produce the best prediction of the FBBR biomass concentration compared to other reported correlations. The average biomass concentration in the FBBR decreased with the increase of the superficial velocity in the range of 45-65 m/h at all applied nitrogen loadings (i.e. 6, 8, 12 and 16 kg N/m3bedd).

Biofilms↗
PubMed2000

[Observation of biofilms inside tracheal tubes by electron microscopy and the relationship between biofilms and VAP].

OBJECTIVE: To observe the formation of biofilms inside tracheal tubes and to evaluate the effect of biofilm on the development of ventilator associated pneumonia (VAP). METHODS: Biofilms inside tracheal tubes from intubated patients were observed by scanning electron microscopy and transmission electron microscopy, meanwhile bacteria were detected in the specimens from the lower respiratory tract and the inside of tracheal tubes. RESULTS: 76% (19/25) of inner surface of tracheal tubes was coated with a confluent amorphous matrix by scanning electron microscopy. The average duration of trach-intubation in this group [(10.7 +/- 7.9) days] was longer than that in the other group [(2.1 +/- 0.8) days] in which tracheal tubes were not coated with the confluent amorphous matrix (P < 0.05). The presence of many bacteria(14/18) within these amorphous matrix was confirmed by transmission electron microscopy. Of the sixteen tracheal tubes, eleven tubes grew the same organisms that had been isolated from the secretions of the lower respiratory tract before extubation. In some VAP patients (7/8), organisms isolated from tracheal tubes were the same organisms which were pathogenic organisms of VAP. CONCLUSIONS: There was a close connection between the formation of bacterial BF and the long-term indwelling tracheal tubes. The presence of bacterial BF in the inner of tracheal tubes might be associated with the pathogenic organisms of VAP.

Adult↗
PubMed2005

Biomass concentration and biofilm characteristics in high-performance fluidized-bed biofilm reactors.

Two laboratory scale fluidized-bed biofilm reactors (FBBRs) were used to investigate the biomass concentration and the biofilm characteristics in a high performance FBBR used for the denitrification of exceptionally high-nitrate wastewater (1000 mg-N/L). Reported correlations by other workers for predicting the biomass concentration in FBBR were examined for their validity in comparison with the experimental results of this study and the best set of applicable correlations was recommended. The effects of the two main operational parameters, the superficial velocity and nitrogen loading rate on the biomass concentration in the FBBR were also studied. Correlations for the drag coefficient and the expansion index from the literature, together with the biofilm dry density correlation produced from this study were found to produce the best prediction of the FBBR biomass concentration compared to other reported correlations. The average biomass concentration in the FBBR decreased with the increase of the superficial velocity in the range of 45 to 65 m/h at all the applied nitrogen loadings (i.e. 6, 8, 12 and 16 kg-N/m3(bed).d).

Biofilms↗
PubMed2005

Anaerobic growth of Candida albicans does not support biofilm formation under similar conditions used for aerobic biofilm.

C. albicans is an opportunistic fungus causing life-threatening systemic infections particularly in immunocompromised individuals. The organism is a commensal in humans and grows either aerobically, e.g., the oral cavity, or anaerobically, e.g., the gut. We studied anaerobic growth of C. albicans in a defined yeast nitrogen base dextrose medium after adaptation and subculturing in an anaerobic chamber. At 37 degrees C in suspension culture, much slower growth was observed anaerobically with a generation time of 248 min compared to 98 min for aerobic growth. Although the organism grew well on solid medium, shaking increased the growth rate in suspension culture at 37 degrees C. Growth was enhanced at acidic pH compared to neutral or alkaline pH. Cells grown anaerobically produced hyphae, but did not produce biofilm on plastic surface or denture acrylic under either static conditions or with mild shaking, conditions that support aerobic biofilm formation.

Aerobiosis↗
PubMed2003

Monitoring biofilm formation by using cyclic voltammetry-effect of the experimental conditions on biofilm removal and activity.

The effect of experimental conditions on cyclic voltammetry experiments on platinum electrodes covered with biofilms formed by Pseudomonas fluorescens for 2 hours was investigated. Results show that recycling the potential stabilizes the shape of the cyclic voltammogram after 195 cycles, but the observation of the electrodes by epifluorescence microscopy showed that cells are still adhered to the platinum surface. Some experimental conditions were changed during the electrochemical measurements--sweep rate, pH of the buffer and applied potential range. Some of these parameters had a strong impact on the bacteria that are adhered to the surface, increasing the death and removal in some circumstances.

Biofilms↗
PubMed2004

Enhancement of biofilm formation onto surface-modified hollow-fiber membranes and its application to a membrane-aerated biofilm reactor.

Surface-modified hollow-fiber membranes were prepared by radiation-induced grafting of an epoxy-group-containing monomer, glycidylmethacrylate (GMA), onto a polyethylene-based fiber (PE-fiber). The epoxy ring of GMA was opened by introduction of diethylamine (DEA). The bacterial adhesivity to this material (DEA-fiber) was tested by immersion into a nitrifying bacterial suspension. The initial adhesion rates and the amount of attached bacteria of the DEA-fiber were 6-10-fold and 3-fold greater than those of the PE fiber, respectively. A membrane-aerated biofilm reactor (MABR) composed of DEA fibers was developed for partial nitrification with nitrite accumulation. Prior to the nitrification test, it was confirmed that the oxygen supply rate (OSR) was proportional to air pressure up to 100 kPa, allowing easy control of oxygen supply. Stable nitrite accumulation was observed in the partial nitrification test at a fixed oxygen supply throughout the operation period, indicating that oxygen was consumed only by ammonia oxidizers. Furthermore, it was demonstrated that oxygen utilization efficiency (OUE) in the ammonia oxidation process was nearly 100% after 300 h incubation.

Ammonia↗