Endophytic bacteria play a central role in plant health, yet their diversity and functions in medicinal plants remain poorly characterized. In this study, we integrated high-throughput sequencing, culture-based isolation, functional assays, and greenhouse validation to characterize the endophytic microbiome of Melissa officinalis L. High-throughput sequencing revealed 347 species with strong tissue-specific structuring. Paucibacter and Pseudomonas genera related to phylum Pseudomonadota dominated in all plant tissues. Nineteen culture-dependent strains representing Pseudomonas, Microbacterium, Plantibacter, Agreia, and Kocuria demonstrated various plant growth-promoting traits, including phosphate solubilization, nitrogen fixation, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, indole-related compounds (IRC) production, siderophore secretion, and hydrolytic enzyme activities (chitinase, protease, and lipase). Pseudomonas fluorescens XIEG-4RS14 showed antifungal activity against Fusarium graminearum (50%) and F. moniliforme (37%), P. marginalis XIEG-4RS15 showed 100 and 62%, P. baetica XIEG-4RS18 showed 28 and 42%, P. fluorescens XIEG-4RS32 showed 45 and 39%, and P. rhodesiae XIEG-4RS37 showed 58 and 27% respectively. Greenhouse assays demonstrated that strains Pseudomonas fluorescens XIEG-4RS14, P. fluorescens XIEG-4RS32, P. taetrolens XIEG-4RS19, and P. poae XIEG-4RS27 increased wheat root and shoot dry weight by up to 113% to 60% respectively. These findings revealed that M. officinalis harbors highly cooperative and functionally effective endophytes with strong potential as next-generation bioinoculants for sustainable crop production.
Shurigin et al. (Fri,) studied this question.