Showing papers on "Biofilm published in 1994"
TL;DR: Aerobic biofilms were found to have a complex structure consisting of microbial cell clusters (discrete aggregates of densely packed cells) and interstitial voids, implying that to accurately describe biofilm activity, the relation between the arrangement of structural components and mass transfer must be undrstood.
Abstract: Aerobic biofilms were found to have a complex structure consisting of microbial cell clusters (discrete aggregates of densely packed cells) and interstitial voids. The oxygen distribution was strongly correlated with these strutures. The voids facilitated oxygen transport from the bulk liquid through the biofilm, supplying approximately 50% of the total oxygen consumed by the cells. The mass transport rate from the bulk liquid is influenced by the biofilm structure; the observed exchange surface of the biofilm is twice that calculated for a simple planar geometry. The oxygen diffusion occurred in the direction normal to the cluster surfaces, the horizontal and vertical components of the oxygen gradients were of equal importance. Consequently, for calculations of mass transfer rates a three-dimensional model is necessary. These findings imply that to accurately describe biofilm activity, the relation between the arrangement of structural components and mass transfer must be undrstood. (c) 1994 John Wiley & Sons, Inc.
793 citations
TL;DR: A model system for studying Candida biofilms growing on the surface of small discs of catheter material is described and could be used for testing the efficacy of antifungal agents against biofilm cells.
Abstract: A model system for studying Candida biofilms growing on the surface of small discs of catheter material is described. Biofilm formation was determined quantitatively by a colorimetric assay involving reduction of a tetrazolium salt or by [3H]leucine incorporation; both methods gave excellent correlation with biofilm dry weight (r = 0.997 and 0.945, respectively). Growth of Candida albicans biofilms in medium containing 500 mM galactose or 50 mM glucose reached a maximum after 48 h and then declined; however, the cell yield was lower in low-glucose medium. Comparison of biofilm formation by 15 different isolates of C. albicans failed to reveal any correlation with pathogenicity within this group, but there was some correlation with pathogenicity when different Candida species were tested. Isolates of C. parapsilosis (Glasgow), C. pseudotropicalis, and C. glabrata all gave significantly less biofilm growth (P
601 citations
TL;DR: A model biofilm consisting of Pseudomonas aeruginosa, pseudomonas fluorescens, and Klebsiella pneumoniae was developed to study the relationships between structural heterogeneity and hydrodynamics.
Abstract: A model biofilm consisting of Pseudomonas aeruginosa, Pseudomonas fluorescens, and Klebsiella pneumoniae was developed to study the relationships between structural heterogeneity and hydrodynamics. Local fluid velocity in the biofilm system was measured by a noninvasive method of particle image velocimetry, using confocal scanning laser microscopy. Velocity profiles were measured in conduit and porous medium reactors in the presence and absence of biofilm. Liquid flow was observed within biofilm channels; simultaneous imaging of the biofilm allowed the liquid velocity to be related to the physical structure of the biofilm.
425 citations
TL;DR: It is suggested that transport limitations may be an important factor in the antimicrobial resistance of biofilm bacteria and that ATR/FT-IR spectrometry may be used to follow the time course of antimicrobial action in biofilms in situ.
Abstract: Bacterial infections associated with indwelling medical devices often demonstrate an intrinsic resistance to antimicrobial therapies. In order to explore the possibility of transport limitation to biofilm bacteria as a contributing factor, the penetration of a fluoroquinolone antibiotic, ciprofloxacin, through Pseudomonas aeruginosa biofilms was investigated. Attenuated total reflection Fourier transform infrared (ATR/FT-IR) spectrometry was employed to monitor bacterial colonization of a germanium substratum, transport of ciprofloxacin to the biofilm-substratum interface, and interaction of biofilm components with the antibiotic in a flowing system. Transport of the antibiotic to the biofilm-substratum interface during the 21-min exposure to 100 micrograms/ml was found to be significantly impeded by the biofilm. Significant changes in IR bands of the biofilm in regions of the spectrum associated with RNA and DNA vibrational modes appeared following exposure to the antibiotic, indicating chemical modification of biofilm components. These results suggest that transport limitations may be an important factor in the antimicrobial resistance of biofilm bacteria and that ATR/FT-IR spectrometry may be used to follow the time course of antimicrobial action in biofilms in situ.
364 citations
TL;DR: It is apparent from the data that has been reviewed that the potential for the development of microbial biofilms in the environment of the food processing plant exists, and the cleaning and sanitizing practices carried out in the food industry have been shown to control biofilm formation on food contact surfaces.
352 citations
TL;DR: The results demonstrate that the mutants were impaired in the accumulative phase of biofilm production by S. epidermidis by mediating intercellular adhesion.
Abstract: The primary attachment to polymer surfaces followed by accumulation in multilayered cell clusters leads to production of Staphylococcus epidermidis biofilms, which are thought to contribute to virulence in biomaterial-related infections. We isolated Tn917 transposon mutants of biofilm-producing S. epidermidis 13-1, which were completely biofilm negative. In pulsed-field gel electrophoresis no obvious deletions of the mutants were noted. The Tn917 insertions of mutants M10 and M11 were located on different EcoRI fragments but on identical 60-kb SmaI and 17-kb BamHI chromosomal fragments. Linkage of transposon insertions of mutants M10 and M11 with the altered phenotype was demonstrated by phage transduction, whereas the several other mutants apparently represented spontaneous variants. In a primary attachment assay with polystyrene spheres, no significant difference between any of the mutants and the wild type could be detected. Cell clustering as an indication of intercellular adhesion, which is a prerequisite for accumulation in multilayered cell clusters, was not detected with any mutant. These results demonstrate that the mutants were impaired in the accumulative phase of biofilm production. Mutants M10 and M11 did not produce detectable amounts of a specific polysaccharide antigen (D. Mack, N. Siemssen, and R. Laufs, Infect. Immun. 60:2048-2057, 1992), whereas substantially reduced amounts of antigen were produced by the spontaneous variants. Hexosamine was determined as the major specific component of the antigen enriched by gel filtration of biofilm-producing S. epidermidis 1457 because almost no hexosamine was detected in material prepared from the isogenic biofilm-negative transductant 1457-M11, which differentiates the antigen from other S. epidermidis polysaccharide components. Our results provide direct genetic evidence for a function of the antigen in the accumulative phase of biofilm production by S. epidermidis by mediating intercellular adhesion.
343 citations
TL;DR: Spatial relationships among members of the community were distinctive to diclofop-grown biofilms, and unique consortial relationships indicated that syntrophic interactions may be necessary for optimal degradation of dicLofop methyl and other chlorinated ring compounds.
Abstract: Diclofop methyl, a commercial herbicide, was used as the sole carbon source to cultivate diclofop-degrading biofilms in continuous-flow slide culture. The biofilms were analyzed by using scanning confocal laser microscopy and image analysis. Spatial relationships among members of the community were distinctive to diclofop-grown biofilms. These relationships did not develop when the biofilms were grown on more labile substrates but were conserved when the biofilms were cultivated with other chlorinated ring compounds. The structures included conical bacterial consortia rising to 30 μm above the surrounding biofilm, grape-like clusters of cocci embedded in a matrix of perpendicularly oriented bacilli, and other highly specific patterns of intra- and intergeneric cellular coaggregation and growth. These unique consortial relationships indicated that syntrophic interactions may be necessary for optimal degradation of diclofop methyl and other chlorinated ring compounds. Images
330 citations
TL;DR: It is shown that biofilm bacteria are readily killed by an antibiotic on all areas of the active electrodes and on the surfaces of conductive elements that lie within the electric field but do not themselves function as electrodes.
Abstract: The bioelectric effect, in which electric fields are used to enhance the efficacy of biocides and antibiotics in killing biofilm bacteria, has been shown to reduce the very high concentrations of these antibacterial agents needed to kill biofilm bacteria to levels very close to those needed to kill planktonic (floating) bacteria of the same species. In this report, we show that biofilm bacteria are readily killed by an antibiotic on all areas of the active electrodes and on the surfaces of conductive elements that lie within the electric field but do not themselves function as electrodes. Considerations of electrode geometry indicate that very low (< 100 microA/cm2) current densities may be effective in this electrical enhancement of antibiotic efficacy against biofilm bacteria, and flow experiments indicate that this bioelectric effect does not appear to depend entirely on the possible local electrochemical generation of antibacterial molecules or ions. These data are expected to facilitate the use of the bioelectric effect in the prevention and treatment of device-related bacterial infections that are caused by bacteria that grow in biofilms and thereby frustrate antibiotic chemotherapy.
306 citations
TL;DR: This work suggests that the use of copper tubing in water systems may help to limit the colonization of water systems by L. pneumophila.
Abstract: Survival and growth of Legionella pneumophila in both biofilm and planktonic phases were determined with a two-stage model system. The model used filter-sterilized tap water as the sole source of nutrient to culture a naturally occurring mixed population of microorganisms including virulent L. pneumophila. At 20 degrees C, L. pneumophila accounted for a low proportion of biofilm flora on polybutylene and chlorinated polyvinyl chloride, but was absent from copper surfaces. The pathogen was most abundant on biofilms on plastics at 40 degrees C, where it accounted for up to 50% of the total biofilm flora. Copper surfaces were inhibitory to total biofouling and included only low numbers of L. pneumophila organisms. The pathogen was able to survive in biofilms on the surface of the plastic materials at 50 degrees C, but was absent from the copper surfaces at the same temperature. L. pneumophila could not be detected in the model system at 60 degrees C. In the presence of copper surfaces, biofilms forming on adjacent control glass surfaces were found to incorporate copper ions which subsequently inhibited colonization of their surfaces. This work suggests that the use of copper tubing in water systems may help to limit the colonization of water systems by L. pneumophila.
306 citations
TL;DR: Failure of glycopeptide antibiotics to cure prosthesis-related infection is not due to poor penetration of drugs into biofilm but likely due to diminished antimicrobial effect on bacteria in the biofilm environment.
Abstract: To evaluate the adequacy of penetration of antibiotics into biofilm, a novel in vitro model for prosthesis-related infection was developed. Sterile stainless steel orthopedic nuts were incubated with slime-producing Staphylococcus epidermidis. Biofilm-covered nuts were exposed to varying concentrations of vancomycin; then biofilms were harvested. Vancomycin levels in biofilm, as measured by fluorescent polarization immunoassay, far exceeded the MIC and MBC of vancomycin for the organism. Bacterial growth in biofilm was inversely related to vancomycin concentration in biofilm, but even extremely high drug concentrations did not eradicate bacteria embedded in biofilm. The MICs and MBCs for bacteria recovered from biofilm did not differ from those for incubating organisms. Thus, failure of glycopeptide antibiotics to cure prosthesis-related infection is not due to poor penetration of drugs into biofilm but likely due to diminished antimicrobial effect on bacteria in the biofilm environment.
222 citations
TL;DR: The effect of hydraulic retention time and of substrate loading rate on the formation of biofilms were investigated and it was found that at longer hydraulic retention times, a low amount of attached biomass can be present on the carrier material as patchy biofilm.
Abstract: In this article, the conditions for aerobic biofilm formation on suspended particles, the dynamics of biofilm formation, and the biomass production during the start-up of a Biofilm Airlift Suspension reactor (BAS reactor) have been studied. The dynamics of biofilm formation during start up in the biofilm airlift suspension reactor follows three consecutive stages: bare carrier, microcolonies or patchy biofilms on the carrier, and biofilms completely covering the carrier. The effect of hydraulic retention time and of substrate loading rate on the formation of biofilms were investigated. To obtain in a BAS reactor a high biomass concentration and predominantly continuous biofilms, which completely surround the carrier, the hydraulic retention time must be shorter than the inverse of the maximum growth rate of the suspended bacteria. At longer hydraulic retention times, a low amount of attached biomass can be present on the carrier material as patchy biofilms. During the start-up at short hydraulic retention times the bare carrier concentration decreases, the amount of biomass per biofilm particle remains constant, and biomass increase in the reactor is due to increasing numbers of biofilm particles. The substrate surface loading rate has effect only on the amount of biomass on the biofilm particle. A higher surface load leads to a thicker biofilm.A strong nonlinear increase of the concentration of attached biomass in time was observed. This can be explained by a decreased abrasion of the biofilm particles due to the decreasing concentration of bare carriers. The detachment rate per biofilm area during the start-up is independent of the substrate loading rate, but depends strongly upon the bare carrier concentration.The Pirt-maintenance concept is applicable to BAS reactors. Surplus biomass production is diminished at high biomass concentrations. The average maximal yield of biomass on substrate during the experiments presented in this article was 0.44 +/- 0.08 C-mol/C-mol, the maintenance value 0.019 +/- 0.012 C-mol/(C-mol h). The lowest actual biomass yield measured in this study was 0.15 C-mol/C-mol.
TL;DR: Trisodium phosphate appears to be an effective treatment for reducing populations of C. jejuni, E. coli O157:H7 and S. typhimurium and Listeria monocytogenes and has the potential to be used for reduction of bacterial counts on other food products besides raw poultry or on food and non-food contact surfaces.
TL;DR: Using assays to determine intracellular survival in the presence of gentamicin, it is demonstrated that some strains of P. aeruginosa are able to invade corneal cells during experimental bacterial keratitis in mice.
Abstract: Pseudomonas aeruginosa is considered an extracellular pathogen. Using assays to determine intracellular survival in the presence of gentamicin, we have demonstrated that some strains of P. aeruginosa are able to invade corneal cells during experimental bacterial keratitis in mice. Although intracellular bacteria were detectable 15 min after inoculation, the number of intracellular bacteria increased in a time-dependent manner over a 24-h period. Levels of invasion were similar when bacteria were grown as a biofilm on solid medium and when they were grown in suspension. Intracellular bacteria survived in vitro for at least 24 h, although only minimal bacterial multiplication within cells was observed. P. aeruginosa PAK and Escherichia coli HB101 did not cause disease in this model and were not isolated from corneas after 24 h even when an inoculum of 10(8) CFU was applied. Transmission electron microscopy of corneal epithelium from eyes infected for 8 h revealed that intracellular bacteria were present within membrane-bound vacuoles, which suggests that bacterial entry was an endocytic process. At 24 h, the observation of many bacteria free in the cytoplasm indicated that P. aeruginosa was able to escape the endocytic vacuole. The ability of some P. aeruginosa strains to invade corneal epithelial cells may contribute to the pathogenesis or to the progression of disease, since intracellular bacteria can evade host immune effectors and antibiotics commonly used to treat infection.
TL;DR: The results indicate that polyurethane is readily encrusted and colonized by bacteria in vivo despite antibiotic prophylaxis and newer materials must be sought if effective long-term stenting is to be achieved.
Abstract: Objective To examine the relationship between encrustation and microbial biofilm formation on indwelling ureteric stents.
Patients and methods Ureteric stents from 40 patients were examined for the presence of a microbial biofilm and encrustations. Bacteria in stent biofilms were isolated and identified.
Results A profuse biofilm (> 104 c.f.u. cm3–3) was identified on 1J (28%) stents. Enterococcus faecalis was the most common biofilm organism identified and Proteus spp. were not present. Encrustation was seen in 23 (58%) of stents and was not associated with the level of urinary calcium. The major risk factor for stent encrustation was the presence of urolithiasis. Importantly, there was no causative link between stent biofilm formation and encrustation. Both biofilm formation and encrustation increased with the duration of stenting.
Conclusion The results indicate that polyurethane is readily encrusted and colonized by bacteria in vivo despite antibiotic prophylaxis. Newer materials must be sought if effective long-term stenting is to be achieved.
TL;DR: The role of bacterial biofilm formation in catheter-associated infection, prostatitis and struvite (infected stone) calculogenesis stressing, and the importance ofacterial biofilms in the pathogenesis, persistence and hence the treatment of urinary tract infection are reviewed.
Abstract: The bacterial biofilm theory which describes bacterial populations in natural and pathogenic ecological systems in terms of a free-floating or 'planktonic' population of bacteria interacting with a more important matrix enclosed 'sessile' population of bacteria associated with or adherent to a surface, may help explain some of the problems linked to our understanding the nature of urinary tract infections. This paper reviews the role of bacterial biofilm formation in catheter-associated infection, prostatitis and struvite (infected stone) calculogenesis stressing, the importance of bacterial biofilms in the pathogenesis, persistence and hence the treatment of urinary tract infection.
TL;DR: The model was used to evaluate the plausibility of two mechanisms of biofilm antibiotic resistance by qualitative comparison with data from a well-characterized experimental system and predicted differences between the two cases that could permit these resistance mechanisms to be experimentally distinguished.
Abstract: A computer model of biofilm dynamics was adapted to incorporate the activity of an antimicrobial agent on bacterial biofilm. The model was used to evaluate the plausibility of two mechanisms of biofilm antibiotic resistance by qualitative comparison with data from a well-characterized experimental system (H. Anwar, J. L. Strap, and J. W. Costerton, Antimicrob. Agents Chemother. 36:1208-1214, 1992). The two mechanisms involved either depletion of the antibiotic by reaction with biomass or physiological resistance due to reduced bacterial growth rates in the biofilm. Both mechanisms predicted the experimentally observed resistance of 7-day-old Pseudomonas aeruginosa biofilms compared with that of 2-day-old ones. A version of the model that incorporated growth rate-dependent killing predicted reduced susceptibility of thicker biofilms because oxygen was exhausted within these biofilms, leading to very slow growth in part of the biofilm. A version of the model that incorporated a destructive reaction of the antibiotic with biomass likewise accounted for the relative resistance of thicker biofilms. Resistance in this latter case was due to depletion of the antibiotic in the bulk fluid rather than development of a gradient in the antibiotic concentration within the biofilm. The modeling results predicted differences between the two cases, such as in the survival profiles within the biofilm, that could permit these resistance mechanisms to be experimentally distinguished.
TL;DR: In this paper, a novel methodology is proposed to estimate the adhesion strength of biofilm developed in an attached-growth reactor, where the time variation of adhesion strengths was quantified in the course of formation of a biofilm consisting of denitrifiers, and a strong correlation was observed between the dry density and the extracellular biopolymer content per unit biofilm volume.
TL;DR: The results suggest that growth rate plays a role in mediating resistance of biofilms to antibiotics.
Abstract: Several classes of antibiotics were assessed for activity against non-growing Escherichia coli and cells grown as a biofilm. Antibiotics which had activity against non-growing cells also showed some activity against biofilms. Cephamycins were more active than other cephalosporins, but the most effective antibiotics were imipenem and ciprofloxacin, which were also active against steady state biofilms. However, none of the antibiotics studied was capable of completely eradicating a biofilm. These results suggest that growth rate plays a role in mediating resistance of biofilms to antibiotics.
TL;DR: Bacterial motility conveyed a selective advantage during surface colonization even in aqueous-phase systems not dominated by laminar flow, as confirmed by dual-dilution continuous culture results.
Abstract: The colonization of glass surfaces by motile and nonmotile strains of Pseudomonas fluorescens was evaluated by using dual-dilution continuous culture (DDCC), competitive and noncompetitive attachment assays, and continuous-flow slide culture Both strains possessed identical growth rates whether in the attached or planktonic state Results of attachment assays using radiolabeled bacteria indicated that both strains obeyed first-order (monolayer) adsorption kinetics in pure culture However, the motile strain attached about four times more rapidly and achieved higher final cell densities on surfaces than did the nonmotile strain (203 × 108 versus 557 × 107 cells vial-1) whether evaluated alone or in cocultures containing motile and nonmotile P fluorescens These kinetics were attributed to the increased transport of motile cells from the bulk aqueous phase to the hydrodynamic boundary layer where bacterial attachment, growth, and recolonization could occur First-order attachment kinetics were also observed for both strains by using continuous-flow slide culture assays analyzed by image analysis The DDCC system contained both aqueous and particulate phases which could be diluted independently DDCC results indicated that when cocultures containing motile and nonmotile P fluorescens colonized solid particles, the motile strain replaced the nonmotile strain in the system over time Increasing the aqueous-phase rates of dilution decreased the time required for extinction of the nonmotile strain while concurrently decreasing the overall carrying capacity of the DDCC system for both strains These results confirmed that bacterial motility conveyed a selective advantage during surface colonization even in aqueous-phase systems not dominated by laminar flow
TL;DR: It appears that epilithic microbial biofilms dominate the reactivity of the rock-water interface and may determine the type of minerals formed, which will ultimately become part of the riverbed sediment.
Abstract: Epilithic microbial communities, ubiquitously found in biofilms on submerged granite, limestone, and sandstone, as well as on the concrete support pillars of bridges, were examined in the Speed River, Ontario, Canada. Transmission electron microscopy showed that attached bacteria (on all substrata) were highly mineralized, ranging from Fe-rich capsular material to fine-grained ( Images
TL;DR: A study of the effects of hydrophobic and hydrophilic substrata on the colonization behavior of a marine bacterium, SW5, revealed major differences in the morphology of SW5 on these surfaces, affecting biofilm structure and plasmid transfer when SW5 is the recipient organism.
Abstract: The effects of surfaces on the physiology of bacteria adhering to surfaces or immobilized within biofilms are receiving more interest. A study of the effects of hydrophobic and hydrophilic substrata on the colonization behavior of a marine bacterium, SW5, revealed major differences in the morphology of SW5 on these surfaces. Using epifluorescence, scanning confocal laser, and on-line visualization (time-lapse video) microscopy, the organisms at hydrophobic surfaces were characterized by the formation of tightly packed biofilms, consisting of single and paired cells, whereas those at hydrophilic surfaces exhibited sparse colonization and the formation of chains more than 100 microns long, anchored at the surface by the terminal (colonizing) cell. The results are discussed in terms of the possible factors inducing the observed morphological differences and the significance of these differences in terms of biofilm structure and plasmid transfer when SW5 is the recipient organism.
TL;DR: It is demonstrated that microbial exopolymers can play an important role in the bioaccumulation of contaminants in natural systems and direct transfer and accumulation of the contaminants in protozoa.
Abstract: Scanning confocal laser microscopy was used to directly visualize accumulation of the herbicide diclofop methyl and its breakdown products by a degradative biofilm community, cultivated in continuous-flow cell cultures. Some bacterial cells accumulated these compounds. However, most accumulation occurred in cell capsules and certain regions of the exopolymer matrix. Mass spectroscopic analysis of the biofilm material confirmed accumulation of the parent compound and its breakdown products in the biofilms. Lower molecular weight degradation products were found in the effluent, indicating mineralization of diclofop by the flow cell cultures. Grazing protozoa feeding on the biofilms nonselectively ingested cell capsules and exopolymers, suggesting direct transfer and accumulation of the contaminants in protozoa. These findings demonstrated that microbial exopolymers can play an important role in the bioaccumulation of contaminants in natural systems.
TL;DR: The results of this study clearly indicate that growth as a biofilm markedly influences extracellular virulence factor production by S. epidermidis.
Abstract: Summary: The growth rate of Staphylococcus epidermidis was controlled for populations growing as a biofilm and perfused with supplemented, simple-salts medium. Production of iron chelators, extracellular protease and exopolysaccharide (EPS) by these populations was assessed as a function of specific growth rate and compared to that by planktonic populations grown in the same medium within a chemostat. Perfused biofilms increased their iron chelator and protease production with increasing growth rate. Chemostat populations decreased their production of iron chelators with increasing growth rate, whilst showing much enhanced production of proteases at intermediate growth rates (μ 0·15-0·25 h−1). Production of iron chelator and protease was generally 2-50 times higher by biofilms than by planktonic populations. EPS production was low and relatively unaffected by growth rate for the chemostat cultures (about 0·2 μg per unit cell mass) but high for the attached biofilms, particularly at slow growth rates (about 4 μg per unit cell mass). EPS production within the biofilms decreased markedly with increasing growth rate. At growth rates of 0·35 h−1 and above, the levels of EPS for biofilms and planktonic populations were equivalent. The results of this study clearly indicate that growth as a biofilm markedly influences extracellular virulence factor production by S. epidermidis.
TL;DR: A stable slime-negative mutant is isolated from the wild-type Staphylococcus epidermidis RP62A by mitomycin mutagenesis, which is an important basis for further study of the pathogenesis of polymer-associated S. epidersmidis infections.
Abstract: We have isolated a stable slime-negative mutant, M7, from the wild-type Staphylococcus epidermidis RP62A by mitomycin mutagenesis. Besides its inability to produce slime in the test tube this mutant differed also in two other properties from its parent strain: it lacked the ability to accumulate on a surface, and it did not produce a 115 kDa and a 18 kDa extracellular protein. In all other tested properties such as initial adherence, growth rate, cell-wall composition, surface characteristics, DNA restriction profile, the presence of a 29 kb antibiotic resistance plasmid, and antimicrobial susceptibility profile, M7 was indistinguishable from its wild-type. The mutant is an important basis for further study of the pathogenesis of polymer-associated S. epidermidis infections.
TL;DR: Evaluated the effect of the fluoroquinolone fleroxacin on the architecture of established Pseudomonas fluorescens biofilms and found that approximately 59% of cells within fler oxacin-treated bio films emitted red fluorescence whereas >99% of Cells from control biofilm emitted green fluorescence.
Abstract: Scanning confocal laser microscopy (SCLM) and fluorescent molecular probes were used to evaluate the effect of the fluoroquinolone fleroxacin on the architecture of established Pseudomonas fluorescens biofilms. Control P. fluorescens biofilms were heterogeneous, consisting of cell aggregates extending from the attachment surface to maximum measured depths of approximately 90 mum (mean biofilm depth at 72 h, 42 +/- 28 mum) and penetrated by an array of channels. In contrast, fleroxacin-treated biofilms were less deep (mean biofilm depth at 72 h, 29 +/- 8 mum), varied little in depth over large areas, and consisted of a homogeneous distribution of cells. Fleroxacin also caused cells to elongate, with cells located near the biofilm-liquid interface lengthening significantly more than cells located at the attachment surface. By using SCLM, acridine orange, and image analysis it was found that approximately 59% of cells within fleroxacin-treated biofilms emitted red fluorescence whereas >99% of cells from control biofilms emitted green fluorescence. The fleroxacin-treated cells which emitted red fluorescence were observed to be the population of cells which elongated.
TL;DR: Experiments showed that competition in biofilms resulted in non-uniform spatial distributions of bacterial populations and metabolically active bacteria, which affected the substrate transfer and substrate competition within the biofilm.
TL;DR: It is suggested that the “microcosms” of Cocconeis and their underlying cells not only serve as an inoculum to recolonize the surface when conditions permit but enhance immigration by interrupting flow patterns across the surface.
Abstract: The impact of storm-flow on river biofilm architecture was investigated using transmission (TEM) and scanning (SEM) electron microscopy TEM resin substrata were colonized under light-grown (LG) or dark-grown (DG) conditions for 33 weeks in the Clywedog River, North Wales, prior to exposure to ambient-flow (approx 60 cm·s−1) or storm-flow (approx 235 cm·s−1+ river sediment) in a laboratory flume Line transect methodology was used to quantify information from TEM ultrathin sections of LG material In the LG ambient-flow biofilm, bacteria were more abundant directly adjacent to the substratum and were noticeably denser directly under the adnate diatom Cocconeis Higher in the biofilm, the bacteria were loosely dispersed in the matrix between other cells Cyanobacteria occurred most frequently as single cells but were also found in large “palisade” formations adjacent to the substratum Significant horizontal and vertical nearest-neighbor associations were noted for both bacteria and cyanobacteria Cells of Cocconeis were common adjacent to the substratum, providing shelter to, and often elevated upon, an “organic pad” of bacteria, cyanobacteria, and densely staining exopolysaccharide Cyanobacteria and Cocconeis were resistant to removal by storm-flow, but Cocconeis frustules were sometimes damaged Bacteria in the LG storm-flow samples were less common adjacent to the substratum and were sometimes more dispersed higher in the biofilm than in ambient-flow samples We suggest that storm-flow hydrodynamic forces may redistribute bacteria adjacent to the substratum into higher areas of the biofilm In addition, bacteria and the exopolysaccharide matrix were sometimes removed down to the substratum by storm-flow, unless beneath Cocconeis The DG biofilm consisted almost entirely of bacteria Storm-flow only removed surface growth from DG biofilms, and SEM revealed peritrich stalk abrasion and “blow-down” Pre-disturbance biofilm architecture appears to influence the form of destruction We suggest that the “microcosms” of Cocconeis and their underlying cells not only serve as an inoculum to recolonize the surface when conditions permit but enhance immigration by interrupting flow patterns across the surface
TL;DR: The results suggest that sub-MICs of macrolides and clindamycin suppress biofilm formation by P. aeruginosa and that intractable chronic respiratory tract infections due to P.aerug inosa might be prevented.
Abstract: The in-vitro effects of ten antimicrobial agents on the biofilm formation of Pseudomonas aeruginosa were investigated. The production of alginic acid by mucoid P. aeruginosa cells cultured in agar media with sub-MICs of antimicrobial agents was quantified by high-performance liquid chromatography. Alginic acid production was inhibited by 1/4 MIC of minocycline (P < 0.002) and tobramycin (P < 0.02), and by 1/256-1/1/64 MIC of macrolides (erythromycin, clarithromycin, roxithromycin, and rokitamycin) and clindamycin (P < 0.02), compared with drug-free controls. Piperacillin, ceftazidime, and ofloxacin did not inhibit alginic acid production. The production of exopolysaccharide by non-mucoid P. aeruginosa cells grown on silicone plates in sub-MICs of antimicrobial agents was determined by quantitative tryptophan assay. Exopolysaccharide production was inhibited by 1/16 MIC of macrolides and clindamycin, but not by other antimicrobial agents. Electron microscopy showed that biofilm formation by mucoid and non-mucoid type P. aeruginosa strains was inhibited by sub-MICs of erythromycin and correlated with the in-vitro production of alginic acid and exopolysaccharide. These results suggest that sub-MICs of macrolides and clindamycin suppress biofilm formation by P. aeruginosa and that intractable chronic respiratory tract infections due to P. aeruginosa might be prevented.
TL;DR: A mechanistic model is developed to describe the growth of a film‐forming bacterium which adheres to a substratum through the production of extracellular biopolymers and satisfactorily predicts experimental observations of bacterial growth, attachment and detachment, biopolymer production, and adsorption of polymer onto solid (glass) surfaces.
Abstract: Adsorbent surfaces in natural and engineered systems are frequently modifies by bacterial attachment, growth of a biofilm, and bacterial production of extracellular polymer. Attached cells or sorbed polymers may alter the metal-binding characteristics of the supporting substratum and influence metal partitioning. The interdependent behavior of toxic trace metal partitioning and biofilm development requires description of the interaction between cell growth with its accompanying polymer production and metal speciation. In this article, the first of a two part series, a mechanistic model is developed to describe the growth of a film-forming bacterium which adheres to a substratum through the production of extracellular biopolymers. Each bacterial cell was modeled as a two-component structure consisting of active cell mass and biopolymer. The biopolymer component was further divided into cell-associated and dissolved categories to distinguish which remained naturally bound to cell surfaces from that which did not. Use of this structured model permitted independent description of the dynamics of cell growth, and polymer production, both of which may influence trace metal behavior. Employing parameters obtained from independent experiments as well as published values, the model satisfactorily predicts experimental observations of bacterial growth, attachment and detachment, biopolymer production, and adsorption of polymer onto solid (glass) surfaces. The model stimulated transient and steady-state biofilm systems equally well. In the second article in this series, we describe how this model may be extended and utilized to make predictions of the behavior of transient and steady-state biofilm systems in the presence of a toxic transition metal(Pb). © 1994 John Wiley & Sons, Inc.
TL;DR: In this biofilm system, measures of microbial respiratory activity and culturability yielded widely differing estimates of biocide efficacy, and integrated measures of biofilm respiratory activity, including net oxygen and glucose utilization rates, showed only a 10 to 15% reduction.
Abstract: Biofilm bacteria challenged with monochloramine retained significant respiratory activity, even though they could not be cultured on agar plates. Microbial colony counts on agar media declined by approximately 99.9% after 1 h of disinfection, whereas the number of bacteria stained by a fluorescent redox dye experienced a 93% reduction. Integrated measures of biofilm respiratory activity, including net oxygen and glucose utilization rates, showed only a 10 to 15% reduction. In this biofilm system, measures of microbial respiratory activity and culturability yielded widely differing estimates of biocide efficacy.