Studies on cell grouth and aminc acid requirement of rumen fungi

本研究旨在阐明瘤胃厌氧真菌生长所需的氨基酸，这将有助于提高该生物体的培养和更好地了解其在瘤胃微生态系统中的生态位。研究了绵羊瘤胃分离物Neocallimastix sp.N13对10种必需氨基酸（10 EAA）、8种非必需氨基酸（8 NEAA）和18 EAA的氨基酸需要量。虽然该菌能在以硫酸铵为唯一氮源的培养基中生长，但补充氨基酸，特别是18 AA，极大地促进了该菌的生长。含硫氨基酸（SCAA）的缺失显着降低18 AA的生长刺激作用，和硫化物，而不是硫酸盐，取代SCAA的部分。与18AA补充剂相比，芳香族、支链、酸性、脂肪族和羟基氨基酸以及脯氨酸的单独或组合的省略都在一定程度上降低了真菌生长。一个3氨基酸（亮氨酸，蛋氨酸和组氨酸）补充剂是一个有效的刺激剂的真菌，而其他组合（谷氨酸，蛋氨酸和丝氨酸），已知是有效的新美鞭毛虫patriciarum是无效的。18 AA和8 NEAA对瘤胃内优势度较低的Caecomyces sp. K1的生长也有一定的促进作用，而10 EAA则无此作用。

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.