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Updated: May 11, 2026

Functional Complementation Analysis (FCA): A Laboratory Exercise Designed and Implemented to Supplement the Teaching of Biochemical Pathways
Published on: June 24, 2016
Restoring virulence to mutants lacking subunits of multiprotein machines: functional complementation of a Brucella
Nicolas Sprynski1, Christine Felix, David O'Callaghan
1INSERM, U1047, UFR Médecine, 186, Chemin du Carreau de Lanes, 30908 Nimes Cedex 2, France.
Abstract:
Complementation for virulence of a non-polar virB5 mutant in Brucella suis 1330 was not possible using a pBBR-based plasmid but was with low copy vector pGL10. Presence of the pBBR-based replicon in wildtype B. suis had a dominant negative effect, leading to complete attenuation in J774 macrophages. This was due to pleiotropic effects on VirB protein expression due to multiple copies of the virB promoter region and over expression of VirB5. Functional complementation of mutants in individual components of multiprotein complexes such as bacterial secretion systems, are often problematic; this study highlights the importance of using a low copy vector.
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