Identification and characterization of bacteria isolated from the root nodules of Cycas riuminiana Porto ex Regel

• Main Author: Galvez, Jeffrey B.
• Format: text
• Language: English
• Published: Animo Repository 2009
• Subjects: Root-tubercles; Bacteria; Biology
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/3837; https://animorepository.dlsu.edu.ph/cgi/viewcontent.cgi?article=10675&context=etd_masteral
• Institution: De La Salle University

Thirty three (33) bacterial isolates were obtained from Cycas riuminiana root nodules using congo red-yeast extract mannitol agar (CR-YEMA) as the primary isolation medium. These isolates were characterized in terms of their morphological and biochemical characteristics. Colonial morphologies of the isolates were described after growing them in CR-YEMA after five days of incubation at room temperature. Five colony types were observed among the isolates derived from the root nodules. Majority (19/33) of the isolates yielded red, undulate, wrinkled, dry, large opaque, raised, irregular colonies while less than a quarter (7/33) exhibited white, entire, glistening, butyrous, pinpoint, opaque, convex, circular colonies. More than a quarter (26/33) of the isolates were Gram positive while the rest (7/33) were Gram negative bacilli. Most of the isolates were motile (30/33), catalase positive (33/33), oxidase positive (23/33), and can utilize citrate (30/33) as carbon and energy source. Bacterial isolates were identified using 16S rD A sequence analysis. Rhizobial and non-rhizobial species thrived in the root nodules. The rhizobial species include Bradyrhizobium sp., Bradyrhizobium japonicum, Mesorhizobium sp. and Rhizobium sp. The non-rhizobial species predominantly were soil bacteria which include Bacillus spp. (B. megaterium, B. subtilis and B. amyloliquefaciens), Lysinibacillus sphaericus, Paenibacillus sp., Paenibacillus thailandensis, Friedmanniella sp., and Microbacterium sp. One out of the thirty three isolates yielded an amplicon corresponding to the nodA gene. This isolate designated as EXN24 was identified as Mesorhizobium sp., a rhizobial species.