Isolation of antimicrobial endophytic bacteria in billygoat weed (Ageratum conyzoides L.) collected in Soc Trang province

Abstract

Billygoat weed (Ageratum conyzoides L.), which belongs to Asteraceae species, is known as a rare medicinal plant having high antibacterial activity; however, most of the researchers only concerned oil extraction instead of promising endophytic bacteria inside this weed.  Finding new natural antibiotic is becoming more and more urgent as synthetic antibiotics can cause antibiotic resistant bacteria. As a result, the study isolation of antimicrobial endophytic bacteria from billygoat was done. From 5 samples of billy goat in Soc Trang Province, 45 bacterial strains were isolated on solid PDA media. Most of the bacteria were in rod shape, negative gram, and motile. The experiment of testing antimicrobial ability was done with the disk diffusion test method. In brief, 31 bacterial strains were resistant to E. coli, 29 bacterial strains were resistant to Aeromonas hydrophila and 30 bacterial strains were resistant to Staphylococcus aureus. Surprisingly, there were 20 bacterial strains which were resistant to all 3 harmful bacteria and 12 bacterial strains which were resistant to 2 harmful bacteria. Moreover, 3 bacterial strains, including HR10, HT18, and HL1, had the highest resistance to harmful bacteria. By the combination of chemical, biological properties and identification by molecular biology technique, 3 bacterial strains including  HR10, HT18, and HL1 were identified as Bacillus amyloliquefaciens strain NBRC 15535, Pseudomonas oryzihabitans strain NBRC 102199, Pseudomonas aeruginosa strain DSM 50071 with the identity of 95,19%, 98,39%, and 98,56%  respectively