| Research Abstract |
This study is aimed at elucidating amino acid requirement of rumen anaerobic fungi for their growth, which could contribute to improved culturing of this organisms and better understanding of their niches in the rumen microbial ecosystem. Amino acid requirements of Neocallimastix sp.N13 isolated from sheep rumen were studied with supplements containing 10 essential amino acids (10EAA) or 8 non-essential aminoacids (8NEAA) , or both (18AA). Although the fungus could grow in a medium containing ammonium sulphate as a sole source of nitrogen, amino acid supplement, especially 18AA greatly stimulated fungal growth. Omission of sulphur containing amino acids (SCAA) from 18AA reduced markedly the growth-stimulating effect, and sulphide, but not sulphate, substituted for SCAA partly. Omission of aromatic, branched chain, acidic, aliphatic, and hydroxy amino acids, and proline, singly or in combination, all reduced fungal growth in some degree as compared with 18AA supplement. A 3 amino acids (leucine, methionine, and histidine) supplement was a potent stimulator for the fungus, whereas the other combination (glutamic acid, methionine, and serine) , known to be potent for Neocallimastix patriciarum was ineffective. Growth of Caecomyces sp. K1 less dominant in the rumen was also stimulated with 18AA and 8NEAA,but not with 10EAA.These results suggest that requirements of amino acids for rumen fungal growth may differ among genera, species and even strains.
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