Showing papers on "Biofilm published in 1985"
TL;DR: Data indicate that growth within thick adherent biofilms confers a measure of tobramycin resistance on cells of P. aeruginosa.
Abstract: When disks of urinary catheter material were exposed to the flow of artificial urine containing cells of Pseudomonas aeruginosa, a thick adherent biofilm, composed of these bacteria and of their exopolysaccharide products, developed on the latex surface within 8 h. After this colonization, sterile artificial urine containing 1,000 micrograms of tobramycin per ml was flowed past this established biofilm, and a significant proportion of the bacterial cells within the biofilm were found to be still viable after 12 h of exposure to this very high concentration of aminoglycoside antibiotic. Planktonic (floating) cells taken from the test system just before the exposure of the biofilm to the antibiotic were completely killed by 50 micrograms of tobramycin per ml. The MIC of tobramycin for cells taken from the seeding cultures before colonization of the catheter material, and for surviving cells recovered directly from the tobramycin-treated biofilm, was found to be 0.4 micrograms/ml when dispersed cells were assayed by standard methods. These data indicate that growth within thick adherent biofilms confers a measure of tobramycin resistance on cells of P. aeruginosa.
885 citations
TL;DR: Direct scanning electron microscopy of material obtained during surgical debridement of osteomyelitic bone showed that the infecting bacteria grew in coherent microcolonies in an adherent biofilm so extensive it often obscured the infected bone surfaces.
Abstract: Direct scanning electron microscopy of material obtained during surgical debridement of osteomyelitic bone showed that the infecting bacteria grew in coherent microcolonies in an adherent biofilm so extensive it often obscured the infected bone surfaces. Transmission electron microscopy showed this biofilm to have a fibrous matrix, to contain some host cells, and to contain many bacteria around which matrix fibers were often concentrated. Many bacterial morphotypes were present in these biofilms, and each bacterium was surrounded by exopolysaccharide polymers, which are known to mediate formation of microcolonies and adhesion of bacteria to surfaces in natural ecosystems and in infections related biomaterials. The adherent mode of growth may reduce the susceptibility of these organisms to host clearance mechanisms and antibiotic therapy and thus may be a fundamental factor in acute and chronic osteomyelitis.
309 citations
TL;DR: Based on a continuum approach to the biofilm problem and on mass balance equations, the competition of several microbial species for space and substrates is described and the effect of relative substrate concentrations on biofilm performance and composition is discussed.
155 citations
TL;DR: A sintered glass bead core is used to simulate the spaces and surfaces of reservoir rock in studies of the bacterial plugging phenomenon that affects waterflood oil recovery operations and the presence of particles in the water rapidly decreased the core permeability.
Abstract: We have used a sintered glass bead core to simulate the spaces and surfaces of reservoir rock in studies of the bacterial plugging phenomenon that affects waterflood oil recovery operations. The passage of pure or mixed natural populations of bacteria through this solid matrix was initially seen to promote the formation of adherent bacterial microcolonies on available surfaces. Bacteria within these microcolonies produced huge amounts of exopolysaccharides and coalesced to form a confluent plugging biofilm that eventually caused a >99% decrease in core permeability. Aerobic bacteria developed a plugging biofilm on the inlet face of the core, facultative anaerobes plugged throughout the core, and dead bacteria did not effectively plug the narrow (33-μm) spaces of this solid matrix because they neither adhered extensively to surfaces nor produced the extensive exopolysaccharides characteristic of living cells. The presence of particles in the water used in these experiments rapidly decreased the core permeability because they became trapped in the developing biofilm and accelerated the plugging of pore spaces. Once established, cells within the bacterial biofilm could be killed by treatment with a biocide (isothiazalone), but their essentially inert carbohydrate biofilm matrix persisted and continued to plug the pore spaces, whereas treatment with 5% sodium hypochlorite killed the bacteria, dissolved the exopolysaccharide biofilm matrix, and restored permeability to these plugged glass bead cores.
155 citations
TL;DR: In this article, the diffusion coefficients of three different chemical species in naturally grown, heterotrophic biofilms have been measured and a simple model of mass transfer in a biofilm matrix is developed.
143 citations
TL;DR: It is suggested that growth within thick adherent biofilms confers upon cells of Pseudomonas aeruginosa a large measure of resistance to aminoglycosides and other antibiotics that may help to explain the frequent failure of antibiotic chemotherapy in catheter-associated urinary tract infections.
Abstract: A modified Robbins Device was used to establish coherent biofilms of Pseudomonas aeruginosa on the surface of catheter material in an artificial urine milieu and the ability of an antibiotic to penetrate the biofilm and kill the enclosed bacteria was assessed. The Pseudomonas aeruginosa strain used had been isolated from a patient with urinary tract infection. Although planktonic (floating) cells of the Pseudomonas aeruginosa strain were inhibited by less than 1 mg/l of tobramycin and killed by 50 mg/l, contact with 1,000 mg/l of tobramycin for 12 h failed to kill all the sessile (adherent) bacteria in the biofilms on the surface of the catheter material. Surviving sessile bacteria recovered directly from the exposure to 1,000 mg/l of tobramycin were inhibited by 0.4 mg/l of this agent when tested as dispersed planktonic cells by standard MIC methods. It is suggested that growth within thick adherent biofilms confers upon cells of Pseudomonas aeruginosa a large measure of resistance to aminoglycosides and other antibiotics that may help to explain the frequent failure of antibiotic chemotherapy in catheter-associated urinary tract infections.
117 citations
TL;DR: The algebraic relationship is particularly suited for use in the design of biofilm processes such as trickling filters, rotating biological contactors, anaerobic filters, and fluidized or expanded‐bed reactors.
Abstract: A simplified algebraic expression for biofilm kinetics is developed. This mathematical model assumes Monod‐type biological kinetics and diffusive mass transport. The algebraic expression relates the concentration of substrate at the biofilm surface, and the thickness of the biofilm to the substrate utilization rate. The algebraic relationship is particularly suited for use in the design of biofilm processes such as trickling filters, rotating biological contactors, anaerobic filters, and fluidized or expanded‐bed reactors.
90 citations
TL;DR: A mathematical model has been developed for a fixed‐film biological process that describes bulk liquid transport, diffusional transport of oxygen and organics across a stagnant film, and biochemical reactions by the individual cells within the biofilm.
Abstract: A mathematical model has been developed for a fixed-film biological process (film flow over a flat plate) that describes bulk liquid transport, diffusional transport of oxygen and organics across a stagnant film, diffusional transport of oxygen and organics into the biofilm, biochemical reactions by the individual cells within the biofilm, biofilm growth, and cell density changes within the biofilm due to cellular decay Simulation studies are presented to show how contact time and diffusion layer thickness affect process performance
56 citations
TL;DR: It is concluded that biofilms in continuous culture have the potential to enhance the aerobic degradation of aromatic compounds.
Abstract: Pseudomonas putida ATCC 11172 was grown in continuous culture with phenol as the only carbon and energy source; a culture practically without biofilm was compared with biofilm cultures of differing surface area/volume ratios. The biofilm did not significantly affect the maximal suspended cell concentration in the effluent, but it increased the maximal phenol reduction rate from 0.23 g/liter per h (without biofilm) to 0.72 g/liter per h at the highest biofilm level (5.5 cm2 of biofilm surface per ml of reactor volume). The increase in phenol reduction rate was linear up to the surface area/volume ratio of 1.4 cm2/ml. The continuous cultures with biofilms could tolerate a higher phenol concentration of the medium (3.0 g/liter) than the nonbiofilm system (2.5 g/liter). At higher dilution rates an intermediate product, 2-hydroxymuconic semialdehyde, accumulated in the culture. When the biomass of the effluent started to decrease, the concentration of 2-hydroxymuconic semialdehyde reached a peak value. We conclude that biofilms in continuous culture have the potential to enhance the aerobic degradation of aromatic compounds.
53 citations
TL;DR: The direct and the indirect fluroescent-antibody techniques (FA-technique) were applied to determine the number of specific cells in the biofilm of a fixed-bed reactor which is used for the secondary treatment of wastewater.
Abstract: The direct and the indirect fluroescent-antibody techniques (FA-technique) were applied to determine the number of specific cells in the biofilm of a fixed-bed reactor which is used for the secondary treatment of wastewater. The immune-reaction between fluorescing antibodies and the antigenic surface of the specific cells was prevented by slime covering the bacteria in thick layers. The masking effect could not be removed by physical (heat, ultrasonication, washing) and chemical (detergents, chelating, agents, salts) treatment of the cells.
44 citations
TL;DR: In this article, the diffusion coefficient of three different chemical species in naturally grown, heterotrophic biofilms have been measured, and the influence of the diffusion potential and the donnan potential on the ions have been evaluated by comparing the diffusion coefficients of a positively and negatively charged ion and a neutral molecule in experiments with different background electrolyte concentrations.
TL;DR: In this paper, the effect of DO on cell yield in a fixed film reactor using 1,000 mg/L sucrose as a substrate was evaluated, and the correlations of the biofilm thickness and density with DO and their resultant substrate stabilization rates were examined.
Abstract: This study was conducted to: (1) Evaluate the effect of DO on cell yield in a fixed film reactor using 1,000 mg/L sucrose as a substrate; (2) evaluate the correlations of the biofilm thickness and density with DO and their resultant substrate stabilization rates; and (3) examine the response of biofilm communities as a result of DO and biofilm thickness changes. Data obtained from this study indicate that DO has only a minor effect on the cell yield. However, the thickness of aerobic biofilm is definitely related to DO, or thickness (mm)=(2.08×DO)/(9.2+DO). The biofilm density is also related to its thickness. At a DO of 5 mg/L or lower, the biofilm texture is firm and has a wet density of 27-48mg/cm3. At a higher DO (5–16 mg/L), the biofilm becomes porous and filled with air pockets, with its density being reduced to 25mg/cm3. The biological community in biofilm at a high DO environment (16 mg/L) is predominantly short rods grouped in a chain structure. At a low DO environment (0.5 mg/L), however, the pr...
TL;DR: Support media precoating with denitrifying bacterial biofilms and the various polymers tested did not appear to enhance the rate of initial anaerobic biofilm accumulation.
Abstract: This study investigated the possibility of reducing anaerobic reactor start-up times through the use of various support surfaces or through the use of biological precoating (denitrifying biofilm) and chemical precoating (polymer precoating) as means of enhancing anaerobic biofilm development. Results from the support media variation experiment indicated significant differences among the materials. Support media precoating with denitrifying bacterial biofilms and the various polymers tested did not appear to enhance the rate of initial anaerobic biofilm accumulation.
TL;DR: Pseudomonas putida ATCC 11172 was grown in chemostat on L‐asparagine or phenol as the sole, limiting carbon and energy source and the growth characteristics of a culture where a biofilm was present, were compared with one where theBiofilm was strongly reduced by the grinding and shearing effect of sand suspended in the culture.
Abstract: Pseudomonas putida ATCC 11172 was grown in chemostat on L-asparagine or phenol as the sole, limiting carbon and energy source. The growth characteristics of a culture where a biofilm was present, were compared with one where the biofilm was strongly reduced by the grinding and shearing effect of sand suspended in the culture. In the presence of the intact biofilm, the curve of steady-state biomass versus dilution rate diverged greatly from the theoretical pattern predicted by conventional chemostat models. The sand strongly retarded the biofilm formation and to a high degree restored the shape of the biomass versus dilution rate curve to a more conventional pattern. The maximum specific growth rate (mu(max)) could not be calculated from the biofilm cultures. However using the sand cultures, mu(max) was determined to 0.64 h(-1) with L-asparagine as the carbon source and 0.49 h(-1) with phenol which compare favorably with the respective mu(max) values calculated from batch cultures.Incorporation of sand into strongly agitated cultures is recommended as an efficient and simple means of controlling biofilm formation in continuous cultures. The method may enable the gathering of basic kinetic data difficult to obtain in the presence of biofilm.
01 Jan 1985
TL;DR: In this paper, a continuous flow trickling filter system was used for growing a nitrifying bio-firm with a pump buffer drip system, which achieved a rate of 4 mg N03 -Nil/hr at a (low rate· of 13.9 l/hr).
Abstract: 111 pure cultures of �itrosvmonas, coppt•r is known to c�use +2 a stimulation or nitrific1tio11 al l1>w levels (s_ O.ll'3 mg Cu /l) :ind +2 an inhibition affect at highc!r lt->vels (> 0 . 05 mg Cu /1). Nitrifyi.ng activ.:itcd sluclg�s .:trl� 111uc:h 111l1re tolt'rant of copper showing only 75% +2 inliibtti.011 at 150mg Cu /I. Tht' purpose of this paper was to deterrniw:, thE' coppc>r sensitivity of a nitrifying biof i lm grown in a continuous flow trickling fi.lter system. A conti.nuous fl.ow tri. ckling filter system was built ustng li111l.."stone chips for t·lie hio(ilm suhst"ate. Th� bi1)f'.i lrn wns estnbl islwd from second.:iry e(fluent. Af U•r 1 month, a stable nitriCicati\1n rate of 4 mg N03 -Nil/hr was obtaiiwd at a (low rate· of 13.9 l/hr. A sy11t'1t•tic mt•diurn was then introJuced ;rnrl r-·H ;.·;�s �;t:ibl i.z.ed (6.5 7.5i v.:ith a polyst.:iltic pump buffer drip system for tlw n�st uf th� st11c.ly. lnl1ibi t i;111 st11dil?S at vnrrous copp e r l1:vt'ls (U.(l!)'j ! .0 rng/1