RESUMEN
Actinobacteria that are found in nature have enormous promise for the growth of the pharmaceutical sector. There is a scarce report on the antimicrobial activities of endophytic Actinobacteria from Nigeria. As a result, this study evaluated the Actinobacteria isolated from Nigerian medicinal plants in terms of their biodiversity, phylogenetics, and ability to produce antimicrobial compounds. Following accepted practices, Actinobacteria were isolated from the surface-sterilized plant parts. They were identified using 16S rRNA sequencing, microscopic, and morphological methods. The cell-free broth of Actinobacteria isolates was subjected to antimicrobial assay by agar well diffusion. Molecular evolutionary and genetic analysis (MEGA) version X was used for phylogenetic analysis, and the interactive tree of life (iTOL) version 6.0 was used to view the neighbour-joining method-drawn tree. A total of 13 Actinobacteria were recovered, belonging to three genera including 10 strains of Streptomyces, 2 strains of Saccharomonospora, and only 1 strain of Saccharopolyspora. They showed inhibitory activity against several bacterial pathogens. The phylogenetic tree generated from the sequences showed that our isolates are divergent and distinct from other closely related strains on the database. Further, optimization of the antibiotic production by selected Saccharomonospora sp. PNSac2 was conducted. It showed that the optimal conditions were the ISP2 medium (1-2% w/v salt) adjusted to pH of 8 at 30-32â for 12-14 days. In conclusion, endophytic Actinobacteria dwelling in Nigerian soils could be a promising source of new antibiotics. Future research is warranted because more genomic analysis and characterization of their metabolites could lead to the development of new antibacterial medicines.
Asunto(s)
Actinobacteria , Antiinfecciosos , Plantas Medicinales , Streptomyces , Filogenia , Endófitos , ARN Ribosómico 16S/genética , Nigeria , Antiinfecciosos/metabolismo , Antibacterianos/farmacología , Antibacterianos/metabolismo , Streptomyces/genéticaRESUMEN
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.