Showing papers on "Biofilm matrix published in 1996"

Activity and three-dimensional distribution of toluene-degrading Pseudomonas putida in a multispecies biofilm assessed by quantitative in situ hybridization and scanning confocal laser microscopy.

Abstract: As a representative member of the toluene-degrading population in a biofilter for waste gas treatment, Pseudomonas putida was investigated with a 16S rRNA targeting probe. The three-dimensional distribution of P. putida was visualized in the biofilm matrix by scanning confocal laser microscopy, demonstrating that P. putida was present throughout the biofilm. Acridine orange staining revealed a very heterogeneous structure of the fully hydrated biofilm, with cell-free channels extending from the surface into the biofilm. This indicated that toluene may penetrate to deeper layers of the biofilm, and consequently P. putida may be actively degrading toluene in all regions of the biofilm. Furthermore, measurements of growth rate-related parameters for P. putida showed reduced rRNA content and cell size (relative to that in a batch culture), indicating that the P. putida population was not degrading toluene at a maximal rate in the biofilm environment. Assuming that the rRNA content reflected the cellular activity, a lower toluene degradation rate for P. putida present in the biofilm could be estimated. This calculation indicated that P. putida was responsible for a significant part (65%) of the toluene degraded by the entire community.

A Novel Strategy for Control of Microbial Biofilms through Generation of Biocide at the Biofilm-Surface Interface.

Abstract: Biofilms of a mucoid clinical isolate of Pseudomonas aeruginosa (24 h; ca. 10(sup6) CFU/cm(sup2)) were established by immersion of polymer discs in nutrient broth cultures at 37(deg)C. Biofilms exposed for 30 min to various concentrations (0 to 3 mg/ml) of hydrogen peroxide or potassium monopersulfate were rinsed and shaken vigorously in sterile saline to detach loosely associated cells, and the residual viable attached population was quantified by a blot succession method on agar plates. Incorporation of copper and cobalt phthalocyanine catalysts within the polymers significantly enhanced the activity of these oxidizing biocides towards biofilm bacteria by several orders of magnitude. Biofilms established on the control discs resisted treatment with concentrations of either agent of up to 3 mg/ml. Enhancement through incorporation of a catalyst was such that concentrations of potassium monopersulfate of as low as 20 (mu)g/ml gave no recoverable survivors either on the discs or within the washings. Catalysts such as these will promote the formation of active oxygen species from a number of oxidizing agents such as peroxides and persulfates, and it is thought that generation of these at the surface-biofilm interface concentrates the antimicrobial effect to the interfacial cells and generates a diffusion pump which further provides active species to the biofilm matrix. The survivors of low-concentration treatments with these agents were more readily removed from the catalyst-containing discs than from the control discs. This indicated advantages gained in hygienic cleansing of such modified surfaces.