Endophytic bacterial communities associated with halophytic plants in kebili and Gabes regions of Southern Tunisia

In the arid regions of southern Tunisia, soil and irrigation water salinity represent major challenges to agricultural sustainability. Despite the increasing interest in plant-associated microbes, the role of endophytic bacteria in conferring salt tolerance remains largely unexplored in this context. To address this gap, twenty-two halophytic plants and their associated soils were sampled from five distinct sites across the Kebili and Gabes governorates. Significant differences in soil physicochemical properties were observed between sampling sites. The soils are generally poorly developed, non-fertile (with very low organic matter and high CaCO₃ levels), and highly saline, leading to limited cultivation potential. Molecular identification of plants revealed nine different families and 14 genera, with the Amaranthaceae family being the most prominent, including Atriplex spp. (2), Bassia spp. (2), Suaeda spp. (4), and Halocnemum spp. (1). Bacterial community studies were conducted of both culturable and non-culturable endophyte communities inhabiting the green and root compartments of different halotolerant plants. Endophytic microbiome compositions differed between above-ground and below-ground tissues within the same plant family. A higher prevalence of three phyla Proteobacteria (67.80%), Firmicutes (14.06%), and Actinobacteria (6.57%) was detected across all samples. At the genus level, Acinetobacter, Halomonas, Kushneria, Pseudomonas, Psychrobacter, Stenotrophomonas, and Streptomyces formed the common core microbiome. Functional predictions of endophytic bacteria in halophytes highlighted multiple KEGG functional pathways, indicating recruitment of beneficial bacterial taxa to adapt to extreme hypersaline conditions, including plant growth-promoting, biocontrol, and halophilic bacteria.