Elongation factor-G1A identified as a novel effector protein translocated into cells and a key modulator of Pseudomonas aeruginosa physiology and host cellular responses.

Pseudomonas aeruginosa has two closely related elongation factors, EF-G1A and EF-G1B, which share 90 % sequence similarity. Despite their high sequence homology, the role of EF-G in P. aeruginosa pathogenesis remains not fully understood. In our study, we found that compared to EF-G1B, EF-G1A expression reduced bacterial growth and twitching motility, while increasing swimming motility. Notably, EF-G1A was translocated into host cells in a T6SS-dependent manner. This translocation was significantly reduced, though not completely abolished, in strains with mutations in both the T6SS spike protein VgrG1a and the tube protein Hcp1, suggesting that while EF-G1A translocation is influenced by T6SS, additional components are also involved. Moreover, EF-G1A expression reduced T3SS-mediated morphological alterations, as evidenced by the downregulation of T3SS effectors such as ExoS and ExoT. EF-G1A was also found to suppress activation of the NF-κB signaling pathway, leading to decreased production of inflammatory cytokines including IL-6, IL-8, and TNFα. These findings highlight EF-G1A as a key modulator, affecting both P. aeruginosa physiology and host cellular responses, thereby providing new insights into the complex role of EF-G1A in bacterial pathogenesis.