The Omp85 family protein, TamA, exhibits characteristics of a suitable drug target against Pseudomonas aeruginosa.

The outer membrane (OM) of Gram-negative bacteria is crucial for cell stability and virulence and acts as a permeability barrier. The biogenesis, assembly and regulation of proteins in the OM are, therefore, attractive areas of study that could lead to identifying novel drug targets. The translocation and assembly module (TAM), composed of TamA and TamB, facilitates the insertion of some β-barrel proteins into the OM of Escherichia coli and Klebsiella pneumoniae and has also been implicated in lipid homeostasis. However, its role in Pseudomonas aeruginosa remains mostly uncharacterized. To investigate the TAM's function and drug target potential in P. aeruginosa, we generated both single- and double-gene TAM knockouts and assessed their fitness using competition growth assays against WT strains. The WT significantly outcompeted the TAM mutants, indicating a fitness defect. Proteomic analysis revealed surprisingly similar profiles between WT and the double-knockout strains, while single-knockout strains showed changes in OM proteins and reduced expression of flagellar components consistent with attenuated swimming motility observed in ∆tamA. Single-knockout mutants exhibited differential levels of expression of lipoproteins of the β-barrel assembly machinery, suggesting compensatory OM remodelling. In vivo infection assays using Galleria mellonella larvae demonstrated significantly higher survival rates when infected with TAM mutants, with tamA mutants showing the greatest attenuation in virulence. Our findings demonstrate a role the TAM plays in P. aeruginosa virulence and identify TamA as a potential drug target for the development of new antimicrobial therapies against P. aeruginosa.