Phylogenetic insights and antimicrobial biosynthetic potential of Serratia sp. XAFb12 and Pseudomonas sp. XAFb13 from Xylopia aethiopica.

The extensive distribution of Xylopia aethiopica across the continent of Africa has firmly established its medicinal value in diverse disease management. While its phytochemistry is well established, the diversity, molecular, biochemical, and antimicrobial-biosynthetic characterizations of culturable bacterial endophytes residing in fruits of X. aethiopica have not been studied previously. Additionally, danger continues to loom the global health care and management due to antibiotic resistance; hence, the discovery of microbial natural products especially from endophytes could offer a lasting solution to the quest for novel antimicrobial compounds. In this study, we isolated two bacterial endophytes Serratia sp. XAFb12 and Pseudomonas sp. XAFb13 from fresh X. aethiopica fruit. The 16S rRNA gene sequencing, Vitex biochemical test, Gram staining, and 16S rRNA gene analysis were used to confirm their phenotypic and genotypic profiles. Phylogenetic tree analysis reveals their divergence in a separate branch, indicating their uniqueness. The crude extract of both strains showed inhibition against all tested bacterial and fungal pathogens. The minimum inhibition concentration (MIC) ranged from 2.5 to 10%. Chemical analysis of the crude extracts using gas chromatography-mass spectroscopy (GC-MS) revealed the most abundant compounds to be hydrocinnamic acid, 2-piperidinone, 5-isopropylidene-3,3-dimethyl-dihydrofuran-2-one, and diethyl trisulfide. The bacterial endophytes linked to X. aethiopica were described in this study for the first time in relation to clinically significant pathogens. Our findings imply that crude extracts of the endophytic bacteria from X. aethiopica could be potentially employed as antibiotics. Hence, it is crucial to characterize the active ingredient in further detail for future pharmaceutical applications.