MneA and TerC exhibit distinct roles in manganese detoxification and virulence in Vibrio parahaemolyticus.

Vibrio parahaemolyticus is a significant zoonotic pathogen that severely threatens global public health and aquaculture. Manganese (Mn) acts as a cofactor for numerous enzymes and is crucial for bacterial oxidative stress resistance and virulence. However, excessive Mn is toxic, prompting bacteria to develop diverse Mn detoxification mechanisms. Herein, two genes (mneA and terC) located downstream of the Mn-sensing yybP-ykoY riboswitch were identified in V. parahaemolyticus. The expression of mneA and terC is specifically induced by Mn. The mneA deletion mutant (ΔmneA) exhibited impaired growth in standard (pH 7.3), alkaline (pH 8.4), or weakly acidic (pH 6.8) medium supplemented with Mn. By contrast, the terC deletion mutant (ΔterC) showed growth inhibition under high Mn concentrations in weakly acidic medium. Furthermore, the mneA and terC double mutant (ΔmneA ΔterC) was more sensitive to Mn stress than ΔmneA. Bacterial survival assays revealed that both MneA and TerC protect V. parahaemolyticus against Mn-induced bacteriostasis. Inductively coupled plasma-mass spectrometry showed that the deletion of mneA or terC significantly increases intracellular Mn content. A competitive infection assay using a zebrafish model revealed that mneA contributes to virulence in V. parahaemolyticus, while terC has no such effect. RNA sequencing analysis revealed that V. parahaemolyticus modulates the expression of multiple genes in response to Mn bacteriostatic activity. Collectively, these findings indicate that MneA and TerC exhibit distinct roles in Mn detoxification and virulence in V. parahaemolyticus. This work expands the understanding of Mn detoxification mechanisms in bacteria and highlights the role of Mn in the host-pathogen interface.IMPORTANCEManganese (Mn) is important for life, but is toxic in excess. Consequently, bacteria have evolved elaborate mechanisms to maintain intracellular Mn homeostasis. In this study, we identified and characterized two Mn exporters, that is, MneA and TerC, in Vibrio parahaemolyticus, a significant zoonotic pathogen. We showed that MneA and TerC protect V. parahaemolyticus against Mn-induced bacteriostasis via Mn efflux. Strikingly, unlike the findings in Escherichia coli that a TerC homolog Alx tunes intracellular Mn concentration at alkaline pH, V. parahaemolyticus TerC facilitates the bacterium's growth under high Mn concentrations in weakly acidic medium. Moreover, MneA is crucial for the virulence of V. parahaemolyticus, whereas TerC plays no apparent role. Collectively, while both MneA and TerC act as Mn exporters in V. parahaemolyticus, they exhibit distinct roles. This study also highlights the importance of exploring conserved proteins in different bacterial species.