Microbiological Studies of the Intestinal Microflora of the Koala, Phascolarctos cinereus. I. Colonisation of the Caecal Wall by Tannin-protein-complex- degrading Enterobacteria
R. OsawaAD, P. S. BirdB, D. J. HarbrowB, K. OgimotoC and G. J. SeymourB
A Veterinary Service and Research, Lone Pine Koala Sanctuary, Fig Tree Pocket, Qld 4069, Australia. Present address: Department of Food Microbiology, School of Medicine, University of Tokushima, 18-15, 3-chome, Kuramoto-cho, Tokushima 770, Japan.
B Oral Biology and Pathology, Department of Dentistry, The University of Queensland, Qld 4072, Australia.
C Department of Animal Microbiology, Tohoku University, Sendai 981, Japan.
D To whom all correspondence should be addressed.
The tannin-protein-complex-degrading enterobacterium (T-PCDE), which specifically colonises the caecal wall of the koala, was investigated immunohistologically. Polyclonal antisera were raised against three strains of T-PCDE. Tissue from six koalas was subjected to immunogold staining using a pooled, absorbed antiserum. Numerous T-PCDE cells were observed in the bacterial layer attached to the caecal wall of five of the animals. The distribution pattern of T-PCDE varied: cells were either scattered throughout the bacterial layer or congregated in areas that apparently contained debris of digesta. The sixth animal, which had been treated with oxytetracycline and showed severe loss of body weight, did not have any bacterial layer attached to the caecal wall and did not stain positive for T-PCDE. The evidence suggests a symbiotic association between T-PCDE and the koala; the caecal wall and the wall of the proximal colon were 'strategically' colonised by the bacterium, which may facilitate access, although it is likely to be indirect, for the host animal to the nitrogen moiety liberated from breakdown of tannin-protein complexes.