Light-microscopic Visualization of F and Type 1 Pili

Max-Planck-Institut für Biophysikalische Chemie, D-34 Göttingen, FRG ABSTRACT Summary: Methods for the direct visualization of F and type 1 pili of Escherichia coli in the light microscope are described. The method for visualizing F pili is based on the specific adsorption of fluorescent dye-labelled RNA phages to F pili. The best results were obtained with MS2 phages labelled with rhodamine B. Semi-quantitative determination of the amount of F pili is possible. Type 1 pili can be visualized rapidly and specifically by indirect immunofluorescence. Other structures on the cell surface are neither detected by, nor interfere with these assays. By using different fluorescent dyes the two methods can be combined and both F and type 1 pili can be determined in the same sample.