Biomedical subjects

Oskar Wanner

Publications and source records attributed to Oskar Wanner.

4 recordsLinked to original sources

PubMed2006

Emergence of biofilm-forming subpopulations upon exposure of Escherichia coli to environmental bacteriophages.

Exposure of Escherichia coli MG1655 to environmental bacteriophages results in rapid selection for phage-tolerant subpopulations displaying increased biofilm formation. Analysis of one phage-tolerant strain revealed large amounts of the DNA-binding Dps protein in the outer membrane protein and production of fimbria-like structures. In dps and fimA mutant derivatives of MG1655, no selection of phage-tolerant bacteria upon exposure to bacteriophages occurred, suggesting a role for Dps and type I pili in bacteriophage tolerance.

Bacterial Proteins↗

PubMed2005

Effect of heat recovery from raw wastewater on nitrification and nitrogen removal in activated sludge plants.

By recovery of heat from the raw wastewater in the sewer system, the influent temperature of a wastewater treatment plant (WWTP) is reduced. This can have a negative effect on nitrification in the WWTP, since this process strongly depends on temperature. The analysis of the temperature regime in the WWTP of Zurich, Switzerland, revealed that in the cold season, the effluent temperature is about 0.7 degrees C higher than the influent temperature and that nitrification is not affected by a decrease of the influent wastewater temperature lasting for a couple of hours only, but is significantly affected by a longer lasting temperature decrease. Three diagrams were developed with a steady-state model, from which the consequences of a permanent temperature decrease on the nitrification safety factor, aerobic sludge retention time and total nitrogen removal can be evaluated. Using simulations with a dynamic model, calibrated for the Zurich WWTP, a quantitative relationship between the wastewater temperature and the ammonium effluent concentration was established. This relationship can, in combination with measured effluent concentrations of an existing WWTP, be used to predict the increase of the ammonium effluent concentration in this plant resulting from a permanent decrease of the wastewater influent temperature.

Hot Temperature↗

PubMed2004

Results from the multi-species benchmark problem (BM3) using one-dimensional models.

The IWA's Biofilm Modeling Task Group created a multi-species benchmark problem in which heterotrophic bacteria, nitrifying bacteria, and inert biomass coexist in a biofilm. Members of the Task Group submitted solutions from nine different one-dimensional models. The most important distinctions among the models were (1) whether the model required a full numerical solution or was solved with a spreadsheet, and (2) the way the biomass types were distributed in the biofilm. The models that protected the slow-growing species by having them accumulate away from the outer surface always had the largest surface coverage by nitrifiers and inerts, but the heterotroph coverage declined to compensate. Coverage by heterotrophs and removal of substrate COD were most strongly affected by dilution from nitrifiers and inerts near the outer surface. Models that did not allow the nitrifiers and inerts to dilute the heterotrophs significantly in the outer layer predicted more removal of COD than did the other models. The choice of the model to use depends on the user's needs and the relative importance of including protection of slow-growing species and/or dilution of fast-growing species.

Bacteria↗

PubMed2003

Mutual influences of Pseudomonas aeruginosa and Desulfovibrio desulfuricans on their adhesion to stainless steel.

The mutual influences of Pseudomonas aeruginosa PAO1 and Desulfovibrio desulfuricans subsp. desulfuricans (ATCC 29577) on their adhesion to stainless steel were investigated in batch and column experiments. It was found that P. aeruginosa promoted the adhesion of D. desulfuricans under conditions of turbulence, but not under quiescent conditions. The enhancement involved the alignment of most D. desulfuricans along P. aeruginosa cells and was attributed to the additional interaction surface area provided by adhered P. aeruginosa to aligning D. desulfuricans cells. A slightly positive effect of preadhered D. desulfuricans on the adhesion of P. aeruginosa was found. Under condition of laminar flow, substantially better adhesion of D. desulfuricans to confluent P. aeruginosa biofilms than to steel was observed. The mutual influences are discussed in terms of more favorable adhesion energies and the influence of changed hydraulic conditions due to the roughness of P. aeruginosa biofilms.

Bacterial Adhesion↗