Physiological and multi-omic insights into the adaptation mechanisms of Planococcus halotolerans SCU63T to high-salinity and low-temperature co-stress.
High-salinity and low-temperature co-stress often impairs microbial function and disrupts their ecological balance, and thus understanding the adaptive mechanisms of psychrotolerant and halotolerant microorganisms is essential for their application in environmental remediation. The strain Planococcus halotolerans SCU63T can survive under extreme conditions of 15% NaCl and 0 °C. Physiological analyses revealed that, under co-stress, cells developed a thicker capsule, accumulated more intracellular sodium (increased from 2.25 to 3.41 g/kg), and exhibited significantly elevated membrane permeability. Genome annotation identified numerous co-stress-responsive genes, including but not limited to cspA, desA, betA/B, opuA/D, proX, nhaC, mnhA-G, trkA, and trkH. Transcriptomic data further demonstrated that these genes regulate ABC transporters, branched-chain amino acid and osmoprotectant metabolism, membrane transport, and cellular homeostasis. Metabolomic profiling confirmed that, under co‑stress, the strain not only accumulated proline derivatives and upregulated glycosylated products and certain alkaloids, but also underwent significant changes in molecules associated with membrane lipid remodeling and fatty acid derivatives. Collectively, these findings advance our understanding of microbial tolerance to concurrent stressors and provide a promising microbial resource for the remediation of saline soils in winter and high-salt as well as low-temperature industrial wastewater.