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Strain engineering: example of achievement

"Green Bacteria"

Construction of a platform strain from the bacterium Pseudomonas aeruginosa (SM59 model)

From the reference strain PAO1, removal of most genetic elements confering antibiotic resistance, virulence and pathogenicity (efflux systems, enzymes, membrane modification genes, secreted factors, structural factors).
Approx. 1% of genome removed

› Unaltered fitness

› Hypersuceptibility to antibiotics: 
• 2 to 256 fold reduction in resistance to anti-pyocyanic antibiotics

› Decrease in virulence & pathogenicity: 
• -68 % in cytotoxicity to murine macrophages
• -44 % in lung cell adhesion
• -74 % in ability to form biofilm
• -50 % in ability to kill Galleria mellonella larvae

Deleted resistance mechanisms, classified by family:
– Efflux systems: MexAB, MexXY, MexCD, MexEF, MuxABC
– Enzymes: AmpC, APH3’IIb
– Membrane modification: ArnBCDATEF

Deleted virulence mechanisms:
– Elastases: LasA, LasB, AprA
– Exotoxins: ToxA, ExoS, ExoT et ExoY
– Flagellum: FliEFG
– Phospholipase C: PlcH
– Type IV pilus: PilQ
– Rhamnolipid: RhlA
– Quorum Sensing: PqsA, RhlIR, LasIR
– Lectins: LecA, LecB