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Characterization of Gram-negative Anaerobic Strains, Isolated from Koala Feces, which Exhibit Satellite Growth and Pleomorphism 

Ro Osawa1, Tomohiko Fujisawa2, and Tomotari Mitsuoka2

1 Veterinary Service and Research, Lone Pine Koala Sanctuary, Fig Tree Pocket, Brisbane, Australia 4069

Laboratory for Intestinal Flora, Frontier Research Program, Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-01, Japan


Three strains, which showed satellite growth around colonies of concomitant isolates of Escherichia coli, were isolated from koala feces. Experimental inoculation of these strains and E. coli strains on a plate medium anaerobic, gram-negative, and highly pleomorphic rods. They were bile resistant and asaccharolytic, and produced only a trace amount of propionic acid from peptone yeast-extract Fildes-solution with glucose broth. Their growth was stimulated by succinic acid but completely inhibited by fumaric acid. Subsequent biochemical analysis revealed that the strains produced a large amount of propionic acid from peptone yeast-extract (PY) broth supplemented with sodium succinate. A PY broth agar plate, which contained 30% E. coli-metabolized PY broth, enhanced growth of the strains, and it was found that this spent broth contained succinic acid produced by the E. coli. The evidence suggests that the observed satellite growth was due to succinic acid produced by E. coli strains.