Salinity and Phenol-Induced VBNC State of Quorum-Quenching Bacterium and Its Resuscitation Strategies for Biofilm Control in Industrial Wastewater Treatment.

Quorum quenching (QQ) is an effective biological strategy for mitigating membrane biofouling in membrane bioreactors (MBRs), yet the persistence of QQ bacteria under harsh industrial wastewater conditions remains poorly understood. Here, the induction, resuscitation and functional recovery of the viable but nonculturable (VBNC) state in the efficient QQ bacterium Brucella sp. ZJ1 was investigated under salinity and combined phenol-salinity stress. Combined stress markedly accelerated VBNC formation (36 h vs. 10 days under salinity alone) and caused greater oxidative damage, metabolic suppression, structural deterioration and loss of QQ activity. Salinity-induced VBNC cells recovered following stress removal, whereas phenol-salinity-induced cells required resuscitation-promoting factor (Rpf) for efficient revival. Rpf-mediated resuscitation substantially restored both QQ activity and biofilm inhibition capacity. Transcriptomic analysis revealed that VBNC formation was accompanied by coordinated repression of genes involved in central metabolism, DNA replication and protein biosynthesis, together with activation of osmotic adaptation, membrane transport, quorum sensing and oxidative stress response pathways. These findings demonstrate that the VBNC state is an active adaptive strategy that preserves the potential for functional recovery and provides new insights for improving the antifouling performance of QQ-based MBR systems treating high-strength industrial wastewater.