Impact of AbaI Mutation on Virulence, Biofilm Development, and Antibiotic Susceptibility in Acinetobacter baumannii

In this study, we constructed a stable markerless abaI knockout mutant (ΔabaI) strain using a pEXKm5-based allele replacement method to investigate the impact of abaI on A. baumannii. Proteomic analysis revealed significant alterations in protein expression between the wild type (WT) and ΔabaI mutant strains, particularly in proteins associated with membrane structure, antibiotic resistance, and virulence.

Notably, the downregulation of key outer membrane proteins such as SurA, OmpA, OmpW, and BamA suggests potential vulnerabilities in outer membrane integrity, which correlate with structural abnormalities in the ΔabaI mutant strain, including irregular cell shapes and compromised membrane integrity, observed by scanning and transmission electron microscopy. Furthermore, diminished expression of regulatory proteins such as OmpR and GacA-GacS highlights the broader regulatory networks affected by abaI deletion.