Transfer of fluorescin from Ps. pyocyanea to colonies of other bacteria.

Fluorescence under ultra-violet irradiation has been described by one of us as a criterion for the detection of Ps. pyocyanea on culture plates (Lowbury, 1951). In mixed cultures we have recently found colonies showing typical fluorescence which proved on subculture to be Bact. coli. The colonies of the subculture did not fluoresce. It was thought that colonies of these bacteria in the original culture had picked up fluorescin from the medium on which Ps. pyocyanea was also growing. The following experiments were done to test this hypothesis.