America Martinez-Rodriguez

Bacterial outer-membrane vesicles (OMVs) mediate stress tolerance, biofilm formation, and interkingdom communication, but their role in beneficial endophytes remains underexplored. We isolated 11 non-redundant isolates associated with Bacillus, Enterococcus, Kosakonia and Kocuria from Agave tequilana seeds, identified by MALDI-TOF MS and 16S rRNA gene sequencing. We focused on the catalase-negative Enterobacter cloacae SEA01, which exhibits plant-promoting traits and support agave growth under nutrient-poor microcosms. In addition, this endophyte produces OMVs. Time-resolved SEM documented OMV release and cell aggregation within 9 h, followed by mature biofilms at 24 h with continued vesiculation. Purified OMVs (≈80–300 nm) contained extracellular DNA and were characterized by dynamic light scattering and UHPLC–ESI–QTOF-MS lipidomics. The OMV lipidome was dominated by phosphatidylethanolamine (~80%) and was enriched in monounsaturated fatty acids (16:1, 18:1), while the stress-associated cyclopropane fatty acids (17:1, 19:1) were comparatively retained in the whole-cell membranes; OMVs also exhibited reduced ubiquinone-8. SEA01 is catalase-negative, uncommon among plant-associated Enterobacter, suggesting a testable model in which oxidative factors modulate OMV output and biofilm assembly. These may have implications for recognition and redox signaling at the root interface. Future works should combine targeted proteomics/genomics with genetic or chemical disruption of catalase/OMV pathways.

Climatic factors and pathogenic fungi threaten global banana production. Moreover, bananas are being cultivated using excessive amendments of nitrogen and pesticides, which shift the microbial diversity in plants and soil. Advances in high-throughput sequencing (HTS) technologies and culture-dependent methods have provided valuable information about microbial diversity and functionality of plant-associated endophytic communities. Under stressful (biotic or abiotic) conditions, plants can recruit sets of microorganisms to alleviate specific potentially detrimental effects, a phenomenon known as “cry for help”. This mechanism is likely initiated in banana plants infected by Fusarium wilt pathogen. Recently, reports demonstrated the synergistic and cumulative effects of synthetic microbial communities (SynComs) on naturally occurring plant microbiomes. Indeed, probiotic SynComs have been shown to increase plant resilience against biotic and abiotic stresses and promote growth. This review focuses on endophytic bacterial diversity and keystone taxa of banana plants. We also discuss the prospects of creating SynComs composed of endophytic bacteria that could enhance the production and sustainability of Cavendish bananas (Musa acuminata AAA), the fourth most important crop for maintaining global food security.