HPMO colonization of Salicornia europaea is shaped by environmental factors beyond associated microbiome and plant-derived antimicrobials

Salicornia europaea L. is a promising halophyte for saline soil restoration and safe biomass production. We hypothesized that it maintains a core microbiome of microorganisms enhancing adaptation to saline stress. To test this, microbial communities from bulk soil, rhizosphere, roots, and shoots were analyzed at four sites in Poland and Norway, differing in salinity and organic matter content. In addition, we assessed how soil physicochemical properties and meteorological factors influenced plant growth, antioxidant capacity, and colonization by human pathogenic microorganisms (HPMOs). Despite site-specific variation, taxa such as Marinomonas , Hoeflea , Kushneria , Woeseia , Erythrobacter , Altererythrobacter , and Pantoea were consistently associated with S. europaea , indicating a conserved core microbiome. Organic matter alleviated salt stress, supporting plant growth and antioxidant activity. Although S. europaea produces antimicrobial agents, it does not prevent colonization by human pathogenic microorganisms (HPMOs) such as Escherichia coli , Salmonella enterica , and Listeria monocytogenes . These findings emphasize the role of organic matter and microbial interactions in S. europaea performance and its vulnerability to HPMO colonization under saline conditions. • A conserved S. europaea core microbiome persists despite site-specific variation. • Antimicrobial agents in S. europaea do not prevent HPMO colonization. • Soil organic matter affects S. europaea growth and HPMO colonization under salinity.