Molecular Characterization and Antibacterial Potential of Endophytic Fungal isolates from selected Mangroves along the Coastline of Kenya

Abstract

Abstract The increasing emergence and re-emergence of resistant pathogenic microbes causes a health threat to the human population. This study aimed to characterize mangrove endophytic fungi and evaluate their antibacterial activity. Heritiera littoralis, Rhizophora mucronata, Bruguiera gymnorrhiza, Avicennia marina and Xylocarpus granatum species were collected from Tudor Creek, Mida Creek and Gazi Bay. A total of 30 fungal isolates were subjected to molecular identification based on analysis of their ITS gene region. The isolates in the inferred phylogenetic trees were affiliated with the genus Aspergillus. Ethyl acetate and butanol crude extracts of 29 fungal isolates and eight mycelia samples were screened for antibacterial activity against Staphylococcus aureus (ATCC 27853), Escherichia coli (ATCC 25922) and Pseudomonas aeruginosa (ATCC 25923) using the disc diffusion method. A. marina and R. mucronata harboured the most fungal endophytes that showed the highest antibacterial activity. Minimum Inhibitory Concentration (MIC) activity for the seven isolates that exhibited high antibacterial activities against the test microorganisms compared to the positive control was determined. The ethyl acetate extracts of isolates BE5, BA11, LB4 and RC6 showed significantly lower MIC activity compared to the positive control against test microorganisms (𝑃< 0.05). Therefore, this study confirms that mangrove species harbour fungal isolates that have antibacterial activity and hence could serve as a novel source of antibiotics.