Endophytic Bacteria Isolated From Centella Asiatica

Abstract

Discovery of natural sources of actinobacteria has always been of interest to the scientists due to their ability to produce valuable antimicrobial secondary metabolites. It has been reported that endophytic actinomycetes can be isolated from Centella asiatica (L.) Urban - a familiar tropical medicinal plant called “rau ma” in Vietnamese. This project aimed to investigate Centella asiatica as a potential host of endophytic actinobacteria in Vietnam and evaluate the antibacterial potential of these endophytes. Centella asiatica roots were surface-sterilised, then cultured on inorganic salt starch agar (ISP4) and actinomycete isolation agar (AIA). Pure isolates with actinomycete characteristics were subjected to 16S rDNA sequencing for identification. Identified actinomyces then went through ethyl acetate extraction to undergo agar well diffusion assay against Escherichia coli ATCC 35218 and Staphylococcus aureus ATCC 29213. A total of 4 actinomycete isolates were obtained, two of which were identified as Microbispora sp. while one isolate was found to be Micromonospora fluminis, and the other isolate was Saccharopolyspora cebuensis. The ethyl acetate extract of one Microbispora sp. isolate showed strong inhibition against Staphylococcus aureus ATCC 29213, with inhibition zones whose average diameter was 26.5 ± 0.71 mm. It also showed weak inhibition against Escherichia coli ATCC 35218 along with the ethyl acetate extract of the Micromonospora fluminis isolate which generated inhibition zones whose average diameter was 11.0 ± 1.41 mm. In conclusion, this study isolated and identified 4 endophytic actinomycetes from Centella asiatica roots. The ethyl acetate extracts of some of the isolates showed good antimicrobial activity against potential bacterial pathogens.