Heavy-metal-resistant characterization of Salinimicrobium maris sp. nov. potential significance in algal-bacterial interactions with Phaeocystis globosa

Abstract

In heavy metal-contaminated environments, algal-bacterial interactions enhance metal detoxification while reinforcing stress resilience and ecological remediation capacity. However, whether such interactions extend to harmful algal blooms remains unexplored. In this study, we investigated a novel bacterial strain GXAS 041^T isolated from Phaeocystis globosa bloom in Beibu Gulf. Polyphasic taxonomic analysis confirmed its classification within the genus Salinimicrobium. Functional assays revealed the isolate was resistant to heavy metal stress in decreasing order Pb (1250 μM), Zn (750 μM), Cu (500 μM), Cr (400 μM), and Cd (250 μM). Langmuir adsorption isotherms revealed maximum biosorption capacities of 1.67 (Cd), 5.35 (Cr), 4.32 (Cu), 4.11 (Pb), and 6.15 (Zn) mg/g, with mechanisms characterized by SEM-EDS and FTIR analyses. The strain also produced siderophores and IAA, suggesting synergistic roles in metal chelation and stress mitigation. Crucially, binary culture with strain GXAS 041^T increased cell density of P. globosa by 10.1–60.2 % and reduced bioavailable metals by 4.2–32.8 % versus axenic algae. These findings reveal a dual role of Salinimicrobium sp. in metal detoxification and algal growth promotion, providing new insights into phycosphere symbiosis under environmental stress.