Growth and in situ detection of a pathogenic Escherichia coli in biofilms of a heterotrophic water-bacterium by use of 16S- and 23S-rRNA-directed fluorescent oligonucleotide probes

The colonization of biofilms of a benzoate-degrading Gram-positive water bacterium, strain B4, by a pathogenic Escherichia coli was studied in a continuous flow reactor. E. coli added to a fixed bed reactor colonized by B4, was able to grow in the biofilms and subsequently re-enter the free water phase in high numbers. Mixed biofilms of strain B4 and E. coli were also grown on glass slides for detailed examination of the spatial order of the mixed population biofilm. Individual cells as well as microcolonies of E. coli were detected in the biofilms by hybridization with a fluorescently labeled 23S rRNA-targeted oligonucleotide probe. The spatial distribution of E. coli could be analyzed in all layers of even thick biofilms.