Phosphodiesterase BpdE suppress bacterial proliferation by regulating min operon in Brucella abortus

Brucella spp. are intracellular pathogens utilizing a unique, asymmetric cell cycle to survive within host macrophages. While the biogenesis of the replicative niche is well-studied, the intrinsic regulatory circuits that control the Brucella cell cycle remain incompletely understood. Phosphodiesterase (PDEs) modulates c-di-GMP levels and thereby contribute to the bacterial cell cycle. However, little is known about the role of PDEs in the cell cycle and mechanisms of B. abortus. In this study, we firstly demonstrate that BpdE is a high conserved protein across major Brucella species. Deletion of bpdE (ΔbpdE) significantly accelerated bacterial proliferation in vitro and enhanced intracellular survival within host macrophages. We found that ΔbpdE mutant exhibited an accumulation of DNA content compared to B. abortus A19 (WT) and complemented strain (CΔbpdE). BpdE significantly affected the transcription of cell cycle regulators, including the min system. Additionally, we confirmed that the minCDE genes constitute a single operon in B. abortus. Furthermore, β-galactosidase reporter assays demonstrated that BpdE positively regulates the activity of the minCDE promoter. Taken together, we reported that the c-di-GMP phosphodiesterase BpdE represses bacterial proliferation by regulating minCDE operon in B. abortus. Our results provide a novel regulatory axis for bacterial proliferation and offer new insights into the intricate mechanisms of Brucella pathogenesis.