Grebes eat feathers, but the function of feathers in the alimentary tract and the digestion of feathers are poorly understood. In this article, we isolated Bacillus subtilis, a bacterium with strong feather-degrading ability, from the alimentary tract of grebes; we further purified a secretory keratinase with a molecular weight of 42KDa from B. subtilis. The optimal pH of the keratin-degrading reaction was 6.5, which exactly was the pH value in the alimentary tract of grebes. The feathers eaten by grebes can protect wall of the stomach. The feather net in the third chamber of the stomach could filter food and preventpetrous food such as bones from entering the alimentary track. Importantly, feathers could be digested by feather-degrading bacterium to supply the specific amino acids (cysteine and cystine) after fulfilling their protection function. It was suggested that the digestion of feathers in the alimentary tract of grebes was accomplished by the keratin-degrading bacteria.
Key words: Grebes, feather-eating behavior, feather-degrading bacterium, keratinase
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