ISOLATION, IDENTIFICATION AND ANTIBIOTIC SUSCEPTIBILITY OF CURTOBACTERIUM FLACCUMFACIENS STRAIN PM_YT FROM SEA DAFFODIL (PANCRATIUM MARITIMUM L.) SHOOT CULTURES

摘要

After eight years of cultivation of Sea daffodil (Pancratium maritimum L.) shoot cultures at in vitro conditions, bacterial contamination on the plant tissues and medium surface appeared. The contamination was due to endophytic bacterium later isolated as a bacterial strain PM_YT. The colonial characteristics and cell morphology of the isolate were determined after cultivation on YEB-agar medium and coloring of microscopic preparations. The strain identification was implemented by biochemical methods (oxidase and catalase standard strip tests) and nucleotide sequencing of the 16S rRNA gene. The results from the morphological and cultural identification showed that the isolate was Gram-positive bacterium presented from small, short rods, forming small (size of 1-3 mm), round-shaped, yellow- to slightly orange-colored colonies. The results from biochemical identification showed that the strain was oxidase-negative and catalase-positive. The comparative 16S rRNA gene sequence-based phylogenetic analysis revealed 99% pairwise similarity of the strain PM_YT to the bacterial species Curtobacterium flaccumfaciens. Antibiotic susceptibility was implemented by Bauer-Kirby disc diffusion method and the results demonstrated that the isolate was most sensitive to the antibiotics belonging to inhibitors of protein synthesis group, especially to tetracycline, doxycycline, amikacin, rifampin, lincomycin, chloramphenicol, erythromycin, streptomycin and ciprofloxacin.