Brevibacterium EB3 inoculation enhances rhizobacterial community interactions leading to improved growth of Salicornia europaea

Plant growth-promoting bacteria (PGPB) can revolutionize sustainable agriculture by improving crop yields and resilience in the face of climate change and soil degradation. However, one of the challenges of using PGPB is identifying strains that can colonize and establish beneficial relationships with plant hosts and microbiomes. This study examined the effects of single and co-inoculations with three PGPB strains (Brevibacterium casei EB3, Pseudomonas oryzihabitans RL18, and Bacillus aryabhattai SP20) on the rhizosphere microbiome of the halophyte crop Salicornia europaea. 16S rRNA gene amplicon sequencing was used to analyze the rhizosphere bacterial communities' diversity, structure, and composition. PGPB inoculations significantly changed the diversity and structure of the bacterial communities in the rhizosphere, accounting for 74 % of the total variability. The strain B. casei EB3 was the most effective at colonizing the rhizosphere and establishing interactions with other beneficial community members. Notably, the treatments associated with higher plant yield, consistently featured the presence of B. casei EB3 and higher connectivity between this strain and taxa known to promote growth and alleviate salt stress in plants such as Marinobacterium, Pseudomonas and Vibrio. These findings are consistent with bacterial inoculants' direct and indirect effect in boosting bacteria-plant cooperation within the rhizosphere, ultimately leading to a shift towards an optimized rhizosphere and beneficial traits for plants.