Browsing by Author "Roe, Frank L."

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Algal Bioassay:Evaluation of Eutrophication Potential of Stormwater Runoff
(1976) Ward, C. H.; King, J. M.; Characklis, William G.; Roe, Frank L.
Analysis and Monitoring of Heat Transfer Tube Fouling
(1982-10) Zelver, Nick; Flandreau, J. R.; Spataro, W. H.; Chapple, K. R.; Characklis, William G.; Roe, Frank L.
Biofilm penetration and disinfection efficacy of alkaline hypochlorite and chlorosulfamates
(2001-09) Stewart, Philip S.; Rayner, Joanna; Roe, Frank L.; Ree, Wayne M.
AIMS: The purpose of this study was to compare the efficacy, in terms of bacterial biofilm penetration and killing, of alkaline hypochlorite (pH 11) and chlorosulfamate (pH 5.5) formulations. METHODS AND RESULTS: Two-species biofilms of Pseudomonas aeruginosa and Klebsiella pneumoniae were grown by flowing a dilute medium over inclined stainless steel slides for 6 d. Microelectrode technology was used to measure concentration profiles of active chlorine species within the biofilms in response to treatment at a concentration of 1000 mg total chlorine l-1. Chlorosulfamate formulations penetrated biofilms faster than did hypochlorite. The mean penetration time into sim 1 mm-thick biofilms for chlorosulfamate (6 min) was only one-eighth as long as the penetration time for the same concentration of hypochlorite (48 min). Chloride ion penetrated biofilms rapidly (5 min) with an effective diffusion coefficient in the biofilm that was close to the value for chloride in water. Biofilm bacteria were highly resistant to killing by both antimicrobial agents. Biofilms challenged with 1000 mg l-1 alkaline hypochlorite or chlorosulfamate for 1 h experienced 0.85 and 1.3 log reductions in viable cell numbers, respectively. Similar treatment reduced viable numbers of planktonic bacteria to non-detectable levels (log reduction greater than 6) within 60 s. Aged planktonic and resuspended laboratory biofilm bacteria were just as susceptible to hypochlorite as fresh planktonic cells. CONCLUSION: Chlorosulfamate transport into biofilm was not retarded whereas hypochlorite transport was clearly retarded. Superior penetration by chlorosulfamate was hypothesized to be due to its lower capacity for reaction with constituents of the biofilm. Poor biofilm killing, despite direct measurement of effective physical penetration of the antimicrobial agent into the biofilm, demonstrates that bacteria in the biofilm are protected by some mechanism other than simple physical shielding by the biofilm matrix. SIGNIFICANCE AND IMPACT OF THE STUDY: This study lends support to the theory that the penetration of antimicrobial agents into microbial biofilms is controlled by the reactivity of the antimicrobial agent with biofilm components. The finding that chlorine-based biocides can penetrate, but fail to kill, bacteria in biofilms should motivate the search for other mechanisms of protection from killing by antimicrobial agents in biofilms.
Characteristics and management of storm runoff in a planned community
(1975) Characklis, William G.; Zogorski, John S.; Roe, Frank L.
Contributions of antibiotic penetration, oxygen limitation, and low metabolic activity to tolerance of Pseudomonas aeruginosa biofilms to ciprofloxacin and tobramycin
(2003-01) Walters, Marshall C., III; Roe, Frank L.; Bugnicourt, Amandine; Franklin, Michael J.; Stewart, Philip S.
The roles of slow antibiotic penetration, oxygen limitation, and low metabolic activity in the tolerance of Pseudomonas aeruginosa in biofilms to killing by antibiotics were investigated in vitro. Tobramycin and ciprofloxacin penetrated biofilms but failed to effectively kill the bacteria. Bacteria in colony biofilms survived prolonged exposure to either 10 micro g of tobramycin ml(-1)or 1.0 micro g of ciprofloxacin ml(-1). After 100 h of antibiotic treatment, during which the colony biofilms were transferred to fresh antibiotic-containing plates every 24 h, the log reduction in viable cell numbers was only 0.49 +/- 0.18 for tobramycin and 1.42 +/- 0.03 for ciprofloxacin. Antibiotic permeation through colony biofilms, indicated by a diffusion cell bioassay, demonstrated that there was no acceleration in bacterial killing once the antibiotics penetrated the biofilms. These results suggested that limited antibiotic diffusion is not the primary protective mechanism for these biofilms. Transmission electron microscopic observations of antibiotic-affected cells showed lysed, vacuolated, and elongated cells exclusively near the air interface in antibiotic-treated biofilms, suggesting a role for oxygen limitation in protecting biofilm bacteria from antibiotics. To test this hypothesis, a microelectrode analysis was performed. The results demonstrated that oxygen penetrated 50 to 90 micro m into the biofilm from the air interface. This oxic zone correlated to the region of the biofilm where an inducible green fluorescent protein was expressed, indicating that this was the active zone of bacterial metabolic activity. These results show that oxygen limitation and low metabolic activity in the interior of the biofilm, not poor antibiotic penetration, are correlated with antibiotic tolerance of this P. aeruginosa biofilm system.
Diffusivity of cu2+ in calcium alginate gel beads
(1993-03) Chen, D.; Lewandowski, Zbigniew; Roe, Frank L.; Surapaneni, P.
A linear absorption model (LAM) is used to describe the process of metal binding to spherically shaped biopolymers particles. The LAM was solved using a numerical algorithm which calculates diffusivities of metal ion in biopolymer gels. It assumes attainment of rapid metal-biopolymer binding equilibrium accompanied by rate limiting diffusion of the metal ions through the gel. The model was tested using batch experiments in which copper (Cu2+) binding with calcium alginate beads was investigated. Biopolymer density in the beads was varied between 2% and 5%. The diffusion coefficient of Cu2+ calculated from the LAM ranged from 1.19 × 10−9 to 1.48 × 10−9 m2 s−1 (average 1.31 ± 0.21 × 10−9 m2 s−1), independent of biopolymer density. The LAM has theoretical advantages over the shrinking core model (shell progressive model). The latter calculated an unreasonable exponential increase in the diffusion coefficient as density of alginate polymer in the bead increased. © 1993 John Wiley & Sons, Inc.
Diffusivity of cu2+ in calcium alginate gel beads: recalculation
(1994-01) Lewandowski, Zbigniew; Roe, Frank L.
Calculations of the diffusivity of Cu2+ in calcium alginate gel beads using the shrinking core model were checked by us. Corrected results are reported here. Diffusivity was still found to increase with increasing alginate concentration, but at a lower rate than reported in the cited paper. The diffusivity increased by a factor of 2 over the range of alginate concentrations studied rather than 10. The original data is included with sample calculations.
Discriminating between biofouling and scaling in a deposition monitor
(1981) Zelver, Nick; Characklis, William G.; Roe, Frank L.
Effect of catalase on hydrogen peroxide penetration into pseudomonas aeruginosa biofilms
(2000-02) Stewart, Philip S.; Roe, Frank L.; Rayner, Joanna; Elkins, James G.; Lewandowski, Zbigniew; Ochsner, Urs A.; Hassett, Daniel J.
The penetration of hydrogen peroxide into biofilms formed by wild-type and catalase-deficient Pseudomonas aeruginosa strains was measured using microelectrodes. A flowing stream of hydrogen peroxide (50 mM, 1 h) was unable to penetrate or kill wild-type biofilms but did penetrate and partially kill biofilms formed by an isogenic strain in which the katA gene was knocked out. Catalase protects aggregated bacteria by preventing full penetration of hydrogen peroxide into the biofilm.
Effects of biofilm structures on oxygen distribution and mass transport
(1994-05) de Beer, Dirk; Stoodley, Paul; Roe, Frank L.; Lewandowski, Zbigniew
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. © 1994 John Wiley & Sons, Inc.
Monitoring of fouling deposits: a key to heat exchanger management
(1985-09) Roe, Frank L.; Zelver, Nick; Characklis, William G.
The fouling of heat exchanger and other piping or vessel surfaces can be monitored by measuring pressure, flow, temperature, and heat flux, then using the results to calculate fluid frictional resistance. Results can be employed to evaluate treatments for fouling control and study the effect of equipment configurations and operating conditions on containment buildup.
On-line side-stream monitoring of biofouling
(1993) Roe, Frank L.; Wentland, Eric Jon; Zelver, Nick; Warwood, B. K.; Waters, Ralf; Characklis, William G.
Oxygen limitation contributes to antibiotic tolerance of Pseudomonas aeruginosa in biofilms
(2004-06) Borriello, Giorgia B.; Werner, Erin M.; Roe, Frank L.; Kim, Aana M.; Ehrlich, Garth D.; Stewart, Philip S.
The role of oxygen limitation in protecting Pseudomonas aeruginosa strains growing in biofilms from killing by antibiotics was investigated in vitro. Bacteria in mature (48-h-old) colony biofilms were poorly killed when they were exposed to tobramycin, ciprofloxacin, carbenicillin, ceftazidime, chloramphenicol, or tetracycline for 12 h. It was shown with oxygen microelectrodes that these biofilms contain large anoxic regions. Oxygen penetrated about 50 µm into the biofilms, which averaged 210 µm thick. The region of active protein synthesis was visualized by using an inducible green fluorescent protein. This zone was also limited to a narrow band, approximately 30 µm wide, adjacent to the air interface of the biofilm. The bacteria in mature biofilms exhibited a specific growth rate of only 0.02 h-1. These results show that 48-h-old colony biofilms are physiologically heterogeneous and that most of the cells in the biofilm occupy an oxygen-limited, stationary-phase state. In contrast, bacteria in 4-h-old colony biofilms were still growing, active, and susceptible to antibiotics when they were challenged in air. When 4-h-old colony biofilms were challenged under anaerobic conditions, the level of killing by antibiotics was reduced compared to that for the controls grown aerobically. Oxygen limitation could explain 70% or more of the protection afforded to 48-h-old colony biofilms for all antibiotics tested. Nitrate amendment stimulated the growth of untreated control P. aeruginosa isolates grown under anaerobic conditions but decreased the susceptibilities of the organisms to antibiotics. Local oxygen limitation and the presence of nitrate may contribute to the reduced susceptibilities of P. aeruginosa biofilms causing infections in vivo.
Physiology of Pseudomonas aeruginosa in biofilms as revealed by transcriptome analysis
(2010) Folsom, James P.; Richards, Lee A.; Roe, Frank L.; Ehrlich, Garth D.; Parker, Albert E.; Mazurie, Aurélien J.; Stewart, Philip S.
BACKGROUND: Transcriptome analysis was applied to characterize the physiological activities of Pseudomonas aeruginosa grown for three days in drip-flow biofilm reactors. Conventional applications of transcriptional profiling often compare two paired data sets that differ in a single experimentally controlled variable. In contrast this study obtained the transcriptome of a single biofilm state, ranked transcript signals to make the priorities of the population manifest, and compared rankings for a priori identified physiological marker genes between the biofilm and published data sets.RESULTS: Biofilms tolerated exposure to antibiotics, harbored steep oxygen concentration gradients, and exhibited stratified and heterogeneous spatial patterns of protein synthetic activity. Transcriptional profiling was performed and the signal intensity of each transcript was ranked to gain insight into the physiological state of the biofilm population. Similar rankings were obtained from data sets published in the GEO database (www.ncbi.nlm.nih.gov/geo). By comparing the rank of genes selected as markers for particular physiological activities between the biofilm and comparator data sets, it was possible to infer qualitative features of the physiological state of the biofilm bacteria. These biofilms appeared, from their transcriptome, to be glucose nourished, iron replete, oxygen limited, and growing slowly or exhibiting stationary phase character. Genes associated with elaboration of type IV pili were strongly expressed in the biofilm. The biofilm population did not indicate oxidative stress, homoserine lactone mediated quorum sensing, or activation of efflux pumps. Using correlations with transcript ranks, the average specific growth rate of biofilm cells was estimated to be 0.08 h-1.CONCLUSIONS: Collectively these data underscore the oxygen-limited, slow-growing nature of the biofilm population and are consistent with antimicrobial tolerance due to low metabolic activity.
Potential for Monitoring Fouling in the Food Industry
(1985) Zelver, Nick; Roe, Frank L.; Characklis, William G.
Rainfall Quality, Land use, and Runoff Quality
(1979) Characklis, William G.; Ward, C. H.; King, J. M.; Roe, Frank L.
Previous investigators have indicated that air quality may contribute to surface water pollution through rainfall or dry fallout, or both, even to the extent that pollutants travel via the air from industrial and agricultural regions may be deposited in undeveloped areas. Data collected from a heavily developed area in Houston and a forested area 40 miles north were used to estimate the contribution of rainwater quality to stream pollution.
Reaction-diffusion theory explains hypoxia and heterogeneous growth within microbial biofilms associated with chronic infections
(2016-06) Stewart, Philip S.; Zhang, Tian-Yu; Xu, Ruifang; Pitts, Betsey; Walters, Marshall C., III; Roe, Frank L.; Kikhney, Judith; Moter, Annette
Reaction–diffusion models were applied to gain insight into the aspects of biofilm infection and persistence by comparing mathematical simulations with the experimental data from varied bacterial biofilms. These comparisons, including three in vitro systems and two clinical investigations of specimens examined ex vivo, underscored the central importance of concentration gradients of metabolic substrates and the resulting physiological heterogeneity of the microorganisms. Relatively simple one-dimensional and two-dimensional (2D) models captured the: (1) experimentally determined distribution of specific growth rates measured in Pseudomonas aeruginosa cells within sputum from cystic fibrosis patients; (2) pattern of relative growth rate within aggregates of streptococcal biofilm harboured in an endocarditis vegetation; (3) incomplete penetration of oxygen into a Pseudomonas aeruginosa biofilm under conditions of exposure to ambient air and also pure oxygen; (4) localisation of anabolic activity around the periphery of P. aeruginosa cell clusters formed in a flow cell and attribution of this pattern to iron limitation; (5) very low specific growth rates, as small as 0.025 h−1, in the interior of cell clusters within a Klebsiella pneumoniae biofilm in a complex 2D domain of variable cell density.
Resistance of biofilms to the catalase inhibitor 3-amino-1,2,4-triazole
(1998-07) Liu, Xiping; Roe, Frank L.; Jeasaitis, A.; Lewandowski, Zbigniew
Consortia of catalase positive bacteria consisting of Pseudomonas aeruginosa, Pseudomonas fluorescens, and Klebsiella pneumoniae, in both the planktonic form and as biofilms, disproportionate hydrogen peroxide into oxygen and water. The biofilm, however, continued to disproportionate the hydrogen peroxide in the presence of the catalase inhibitor, 3-amino-1,2,4-triazole, while the planktonic organisms did not. While the bacterial catalase–peroxidase–dismutase system was probably responsible for the disproportionation of hydrogen peroxide in both cases, biofilms resisted inhibition of this enzyme system. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 156–162, 1998.
Role of nutrient limitation and stationary-phase existence in klebsiella pneumoniae biofilm resistance to ampicillin and ciprofloxacin
(2003-04) Anderl, Jeff N.; Zahller, Jeff; Roe, Frank L.; Stewart, Philip S.
Biofilms formed by Klebsiella pneumoniae resisted killing during prolonged exposure to ampicillin or ciprofloxacin even though these agents have been shown to penetrate bacterial aggregates. Bacteria dispersed from biofilms into medium quickly regained most of their susceptibility. Experiments with free-floating bacteria showed that stationary-phase bacteria were protected from killing by either antibiotic, especially when the test was performed in medium lacking carbon and nitrogen sources. These results suggested that the antibiotic tolerance of biofilm bacteria could be explained by nutrient limitation in the biofilm leading to stationary-phase existence of at least some of the cells in the biofilm. This mechanism was supported by experimental characterization of nutrient availability and growth status in biofilms. The average specific growth rate of bacteria in biofilms was only 0.032 h−1 compared to the specific growth rate of planktonic bacteria of 0.59 h−1 measured in the same medium. Glucose did not penetrate all the way through the biofilm, and oxygen was shown to penetrate only into the upper 100 μm. The specific catalase activity was elevated in biofilm bacteria to a level similar to that of stationary-phase planktonic cells. Transmission electron microscopy revealed that bacteria were affected by ampicillin near the periphery of the biofilm but were not affected in the interior. Taken together, these results indicate that K. pneumoniae in this system experience nutrient limitation locally within the biofilm, leading to zones in which the bacteria enter stationary phase and are growing slowly or not at all. In these inactive regions, bacteria are less susceptible to killing by antibiotics.
Simulating microbiologically influenced corrosion by depositing extracellular biopolymers on mild steel surfaces
(1996-10) Roe, Frank L.; Lewandowski, Zbigniew; Funk, T.
Electrochemical properties of corroding mild steel (MS) surfaces were measured in real time using three closely spaced microelectrodes. Dissolved oxygen, pH, and ion currents were mapped simultaneously and noninvasively above a MS coupon partially coated with biopolymer gels. Calcium alginate (Ca-Alg [an extracellular biopolymer containing carboxylate functional groups]) and agarose (one without carboxylate functional groups) were tested. Corrosion occurred at approximately the same rate under the two biopolymer spots on the same coupon. Corrosion rates under these biopolymers were ≈ 4 mpy in a weak saline solution. Results suggested corrosion was not influenced by chemical properties of the biopolymer but possibly was controlled by oxygen reduction in noncoated regions of the coupon (i.e., a differential aeration cell).