M. bovis FadR mutant exhibits an altered colony morphotype and increased virulence

FadR, a GntR family transcriptional regulator, is known to maintain fatty acid homeostasis in prokaryotes. In this study, a fadR deletion mutant was generated in Mycobacterium bovis, which exhibited distinct morphological changes, along with enhanced permeability and increased antibiotic susceptibility. Interrupted cell-wall homeostasis often leads to such collateral phenotype. To gain insight into the lipid profile, we conducted lipidomics analysis, which revealed that the levels of DAT and PAT were higher in the mutant, while keto-mycolate methyl esters were lower. Further, key proteins responsible for altered phenotypes and lipid profiles were identified using a comparative proteomics approach between M. bovis and the ΔfadR mutant. In addition to lipid metabolism, several intermediary metabolic and stress response proteins predicted to have roles in the growth, survival, and pathogenicity of mycobacteria were also altered in the mutant. Notably, deletion of fadR led to hypervirulence in the animal model. Taken together, this study establishes a crucial role of FadR in the survival of mycobacteria by regulating lipid metabolism, providing insights into its potential as a target for therapeutic strategies against slow-growing mycobacteria.