Isolation and Morphological Characterization of Endophytic Bacteria from Oryza rufipogan

Abstract

Reports on isolations of endophytic diazotrophic bacteria from wild rice indicate the potential use of such bacteria as alternative nitrogen sources for rice cultivation. Objectives of this study were to isolate local endophyitc bacteria from Oryza rufipogan and to characterize them based on morphology and antibiotic resistance for potential use in future breeding programmes aiming in planta nitrogen fixation. 16 endophytic bacterial colonies were isolated from the roots, stem and leaves of Oryza rufipogan. Cell shapes, colony pigmentation, colony morphology and development were observed. Gram staining was performed for the isolates. Response to selected antibiotics (carbenicillin and cefotaxime dtlOO mg/11 and kanamycin at 50 m g l1 was observed on AG medium at 30 °C for 48 to 72 hours. All isolates were Gram negative. There were long and short rods and round cells of different sizes. One to 3 days were taken for colony development. Twelve isolates were moderately resistant to carbenicillin while isolate 4 and 10 were resistant to cefotaxime and kanamycin, respectively. Isolates of 7(2) and 2(1) showed a better growth on kanamycin containing medium with an average colony diameter of 7 and 6 mm in contrast to that of 6 and 4 mm in control, respectively. Isolate numbers of 2(1) and 6(2) exhibited resistance to all 3 antibiotics. Colony colour varied from yellow, light brown, dark brown and reddish pink. Undulating colony margins and opaque nature (in light transmission) were common. Flat, convex and umbonate elevations were observed. Identification of above morphologically different isolates through 16S rRN analysis will be useful for molecular characterization for experiments on alternative nitrogen for rice in the future