Fig. 7.

Schematic overview of the proposed series of events, leading to the deletion of the ica operon. In the presence of LexA, transcription of recA is prevented, there are no genomic rearrangements and the icaADBC region is present thus resulting in black colonies on CRA plates. Due to mutations, LexA can no longer bind to the promoter region of recA resulting in RecA transcription and activity and the occurrence of genetic rearrangements and deletions. As a result the geh1/lip genes are inverted and the icaADBC region disappears thus resulting in red colonies on CRA plates