Complementation of mrpigG in M. ruber M7. ( a ) Schematic representation of the homologous recombination strategy to construct mrpigG complementation strains ( b ) Construction of mrpigG complementation cassette by double-joint PCR. Lane 1, 5′ flanking region of mrpigG plus mrpigG ORF regions; lane 2, G418 resistance cassette; lane 3, 3′ flanking region of mrpigG ; lane 4, double-joint PCR product. ( c ) Confirmation of mrpigG homologous recombination events. Four primer pairs were used, and PCR amplifications showed distinct bands in different strains. Lane 1, the Δ mrpigG :: mrpigG strain; lane 2, the Δ mrpigG strain. 