Figure 4. Evolutionary aspects of biofilm development as a model of drug resistance in tumours.

a,b | An interpretation of the work by Conibear et al.⁶⁰ studying mutagenesis in biofilm communities of Pseudomonas aeruginosa bacteria containing a green fluorescent protein (GFP) reporter gene that has an inactivating +1 frameshift mutation. In this system, a simple base deletion restores the function of the gene and induces the expression of GFP. a | Biofilm colony growth on a glass substrate. The authors described the possibility that oxidative waste accumulates in microcolonies during biofilm expansion. This waste causes stress-induced mutagenesis and activates GFP expression. b | Top view of a P. aeruginosa biofilm microcolony containing both cells with reactivated GFP and cells without reactivated GFP. c | Biofilm experiments could mimic population dynamics occurring during tumorigenesis and during the development of drug resistance after therapy. In both situations, mutations (depicted by genotypes A and B) can appear in localized environments before spreading to the rest of the tumour. Panel b is reproduced from REF. 60.