Cultivation-dependent characterization of endophytic actinomycetes

Abstract

The opportunity to find new endophytic microorganisms among myriads of plants in different settings and ecosystems is very much appealing. A research to isolate endophytic actinomycetes from ethnobotanical plants in Northern part of the Malay Peninsula has been carried out. We assessed the efficacy of different surface sterilization methods and determined the most suitable medium for isolation of endophytic actinomycetes. The root and stem samples of four plants, Cinnamomum zeylanicum, Zingiber spectabile, Elettariopsis curtisii and Labisia pumila were sterilized and cultured on five isolation media such as Starch Yeast Casein Agar (SYCA), Actinomycetes Isolation Agar (AIA), Humic Acid Vitamin Gellan Gum (HVG), Tap Water Yeast Extract agar (TWYE) and Coal Vitamin Agar (CVA) which were supplemented with cyclohexamide and nystatin. The macro and micro morphological of isolates was observed as well as the chemotaxonomic analysis of the isomer diaminopimelic acid. The surface sterilization method that incorporates an overnight incubation between the use of fungicide/sodium hypochlorite mix and sodium hypochlorite followed by 70% ethanol was effective to eliminate the epiphytic microorganisms. There were 66 isolates of Streptomyces sp. and 1 isolate with unknown genus successfully isolated with the highest recovery of 35.8% obtained from SYCA media followed by 32.8 and 23.9% from AIA and HVG media, respectively. The TWYE and CVA media showed the least isolation of actinomycetes with 6.0 and 1.5%, respectively. Of the total isolates obtained, 61.2% was isolated from the root and 38.8% were isolated from the stem part. Besides that, 56.7% of the endophytic actinomycetes were isolated from the external part of the surface-sterilized plants and 43.3% was isolated from the internal part of the plants. All the 66 isolates were phenotypically grouped into 11 groups based on the presence and color of aerial mycelium, pigment and the morphology of the spore chain. SYCA media is found to be the best among the media tested for isolation of endophytic actinomycetes. A good isolation media is important to increase the number of isolates of endophytic actinomycetes and helps in the discovery of potential bioactive metabolite. © 2010 Academic Journals Inc.