P-245 - Expanding the Role of Demequina: From Marine Carbon Cycling to Plant Salt Stress Alleviation

Salinity stress limits plant growth by disrupting osmotic balance, sugar metabolism, and antioxidant defenses. While plant growth-promoting bacteria (PGPB) enhance stress tolerance, their role in sugar homeostasis remains underexplored. This study investigates Demequina capsici, the first Demequina species described as a PGPB, isolated from the rhizosphere for its potential to modulate sugar accumulation, enhance antioxidant defenses, and alleviate salt stress in plants.

Functional characterization of D. capsici revealed its production of IAA, EPS, ACC deaminase, and hydrolytic enzymes (amylase, cellulase, catalase), suggesting a role in nutrient availability, osmotic regulation, and oxidative stress mitigation. Arabidopsis seedlings inoculated with D. capsici under NaCl stress exhibited higher fresh weight, increased chlorophyll content, proline accumulation, and enhanced antioxidant enzyme activity (CAT, POD, SOD), indicating improved physiological adaptation.

Given that Demequina species are linked to marine carbon cycling, this study examines D. capsici's impact on sugar metabolism. HPLC is quantifying soluble sugars, and RT-qPCR is assessing key sugar transporter and starch metabolism genes. These findings establish D. capsici as a novel plant-associated Demequina species and highlight its role in PGPB-mediated metabolic reprogramming under salt stress.