Fig. 1

a A structural mutation in the production genes (red cross) causes non-function in the production pathway resulting in no product formation from the affected cell. b Plasmid dimer formation during replication results in uneven plasmid distribution in daughter cells and a subpopulation that no longer contains the plasmid harbouring production genes (red cross) and therefore no longer forms product. c The XerCD system of E. coli separates plasmid dimers, limiting the possibility of daughter cells becoming plasmid-free