ENDOPHYTIC BACTERIA DIVERSITY FROM ZINGIBERACEAE AND ANTICANDIDAL CHARACTERIZATION PRODUCED BY Pseudomonas helmanticensis

Abstract

Endophytic microbes are sources for the novel antibiotic. We isolated endophytic bacteria from Zingiberaceae collected from West Sulawesi, Indonesia, and investigated their anticandidal activity. Molecular identification of the isolates was done using 16S rRNA gene sequence analysis. The antimicrobial activity was tested against four bacteria and one yeast. The anticandidal compound of selected bacteria was extracted using three different solvents (chloroform, ethyl acetate, and methanol), and each fraction was tested for their anticandidal activity. Anticandidal minimum inhibitory concentration (MIC) was determined with concentration ranging from 300 to 18.75 μg/mL, and the morphology of the Candida cells after treatment was confirmed by scanning electron microscope (SEM). The identification of anticandidal compounds was conducted using GC-MS. A total of 24 isolates were collected from Zingiberaceae plants. There were 14 genera and 19 species belonging to Gammaproteobacteria (66.67%), Alphaproteobacteria (25.00%), Actinobacteria (4.17%), Bacteriodetes (4.17%), and a new record for Lelliottia aquatilis as an endophytic bacteria. One of 24 isolates identified as Pseudomonas helmanticensis isolated from Alpinia melichroa showed anticandidal activity. Ethyl acetate was the appropriate solvent to extract the anticandidal compounds. Diisooctyl phthalate was found as the most abundant compound in the extract for the anticandidal activity. An increase in extract concentration did not reduce the Candida cell number. The extract treatment showed membrane disruption of Candida albicans cells. We propose that active compounds from P. helmanticensis are potential as anticandidal sources and could be explored more for the pharmaceutical industry.