Lonepinella koalarum gen. nov., sp. nov., a new tannin-protein complex degrading bacterium
Osawa, R, Rainey, F, Fujisawa, T, Lang, E, Busse, HJ, Walsh, TP & Stackebrandt, E 1995, Systematic and Applied Microbiology, vol. 18, no. 1, pp. 368-373.
Osawa and colleagues explored the phylogeny of tannin-protein complex (T-PC)-degrading bacteria within faecal samples from koalas, which led to the proposal of a new genus and species of a bacterium named Lonepinella koalarum after the place at which it was discovered, Lone Pine Koala Sanctuary.
Tannins are biomolecules that bind to proteins to form chemical complexes and typically exist in eucalypts in high concentrations. Koalas, therefore, rely upon T-PC-degrading bacteria for harnessing dietary proteins from their tannin-rich diet. Here, the authors isolated eight strains of T-PC-degrading bacteria from fresh faecal samples of captive koalas. These eight strains could be categorised into four biovars: a, b, c and d. The biochemical characteristics of these biovars were similar, except for biovar d which, unlike the others, was gallate decarboxylase negative. Phylogenetic analysis revealed that biovars a, b and c formed a genetically distinct cluster. For the seven strains within these biovars, the name Lonepinella koalarum was proposed to categorise a new genus and species within the family Pasteurellaceae. The new genus and species are distinct from the other genera within the family Pasteurellaceae due to their degradation of tannin, unique polyamine pattern, negative activities of catalase and oxidase, and low DNA G+C content of 37.5 mol%. The authors provide descriptions for the proposed new genus Lonepinella and species L. koalarum. To summarise, members of the genus Lonepinella are characterised as cells of gram-negative rods of various sizes, facultatively anaerobic, non-motile, and tannase positive, among other factors. L. koalarum can be isolated from both the faeces and the bacterial layer lining the caecum of the koala and is one of the most prevalent bacteria of the animal’s gut flora. The strains grow well on brain heart infusion agar medium at 35OC, but grow well at neither 15OC or 40OC nor on MacConkey agar at 35OC. The species converts gallic acid to pyrogallol (gallate decarboxylase positive) and is positive for β-galactosidase and the Voges-Proskauer reaction. There are several more defining factors of the species detailed in the report.
The proposal of a new genus and species is a notable scientific development in any context, and this particular discovery adds to the growing body of knowledge of the dietary mechanisms that allow the koala to sustain its high-tannin diet.
Summarised by Joanna Horsfall
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