Identification and antibacterial evaluation of endophytic actinobacteria from Luffa cylindrica

Diversity, molecular phylogenetics, and antibiotic biosynthetic potential of endophytic Actinobacteria isolated from medicinal plants in Nigeria

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 30-32℃ 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.

Unraveling the Role of Cytochrome P450 as a Key Regulator Lantipeptide Production in Streptomyces globisporus

The aim of this study was to investigate the regulation of lantipeptide production in Streptomyces globisporus SP6C4, which produces the novel antifungal lantipeptides conprimycin and grisin, and to identify the role of cytochrome P450 (P450) in tis regulation. To investigate the regulation of lantipeptide production, we created gene deletion mutants, including ΔP450, ΔtsrD, ΔlanM, ΔP450ΔtsrD, and ΔP450ΔlanM. These mutants were characterized in terms of their morphology, sporulation, attachment, and antifungal activity against Fusarium oxysporum. The gene deletion mutants showed distinct characteristics compared to the wild-type strain. Among them, the ΔP450ΔlanM double mutant exhibited a recovery of antifungal activity against F. oxysporum, indicating that P450 plays a significant role in regulating lantipeptide production in S. globisporus SP6C4. Our findings highlight the significant role of P450 in the regulation of lantipeptide production and morphological processes in S. globisporus. The results suggest a potential link between P450-mediated metabolic pathways and the regulation of growth and secondary metabolism in SP6C4, thereby highlighting P450 as a putative target for the development of new antifungal agents.

The anticancer and antibacterial potential of bioactive secondary metabolites derived From bacterial endophytes in association with Artemisia absinthium

The continuous search for secondary metabolites in microorganisms isolated from untapped reservoirs is an effective prospective approach to drug discovery. In this study, an in-depth analysis was conducted to investigate the diversity of culturable bacterial endophytes present in the medicinal plant A. absinthium, as well as the antibacterial and anticancer potential of their bioactive secondary metabolites. The endophytic bacteria recovered from A. absinthium, were characterized via the implementation of suitable biochemical and molecular analyses. Agar well diffusion and broth microdilution were used to screen antibacterial activity. SEM was performed to assess the impact of the extracted metabolite on MRSA strain cell morphology. Apoptosis and cytotoxicity assays were used to evaluate anticancer activity against MCF7 and A549. The FTIR, GC-MS were used to detect bioactive compounds in the active solvent fraction. Of the various endophytic bacteria studied, P. aeruginosa SD01 showed discernible activity against both bacterial pathogens and malignancies. The crude ethyl acetate extract of P. aeruginosa SD01 showed MICs of 32 and 128 µg/mL for S. aureus and MRSA, respectively. SEM examination demonstrated MRSA bacterial cell lysis, hole development, and intracellular leaking. This study revealed that the crude bioactive secondary metabolite SD01 has potent anticancer activity. In this study, 2-aminoacetophenone, 1,2-apyrazine-1,4-dione, phenazine and 2-phenyl-4-cyanopyridine were the major bioactive secondary metabolites. In conclusion, our findings indicate that the bacteria recovered from A. absinthium plants and in particular, P. aeruginosa SD01 is a remarkable source of untapped therapeutic, i.e., antimicrobial and anticancer compounds.

Identification and anti-bacterial property of endophytic actinobacteria from Thymes kotschyanus, Allium hooshidaryae, and Cerasus microcarpa

The arbitrary and overuses of antibiotics have resulted in the emergence of multidrug resistance bacteria which encounters human to a serious public health problem. Thus, there is an ever-increasing demand for discovery of novel effective antibiotics with new modes of function against resistant pathogens. Endophytic actinobacteria (EA) have currently been considered as one of the most prospective group of microorganisms for discovery of therapeutic agents. This study aimed to isolate EA from Thymes kotschyanus, Allium hooshidaryae, and Cerasus microcarpa plants and to evaluate their antibacterial properties. The healthy samples were collected, dissected and surface-sterilized before cultured on four different selection media at 28 °C. Nine EA were isolated and identified based on morphological and molecular properties, and scanning electron micrograph analyses. Based on phylogenetic analysis, they were taxonomically grouped into four families Streptomycetaceae, Nocardiaceae, Micromonosporaceae, and Pseudonocardiaceae. Their branched aerial mycelia produced chains of cylindrical or cube or oval shaped spores with smooth or rough surfaces. Four strains; IKBG03, IKBG05, IKBG13, and IKBG17 had less than 98.65% sequence similarity to their closely related strains, which constitute them as novel species/strains. Besides, three strains; IKBG05, IKBG13, and IKBG18 were reported as endophytes for the first time. Preliminary antibacterial activity conducted on the all isolates revealed potent antibacterial effects against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. All isolates strongly inhibited the growth of at least one of the tested pathogens. Our results reveals that the test plants are novel sources for isolating a diverse group of rare and common actinobacteria that could produce a wide range of novel biologically active natural products with antibacterial activity which have a great potential in pharmaceutical and biotechnological applications.