請問培養(yǎng)基的組成成分及其營養(yǎng)物質(zhì)有哪些？
發(fā)布時間：
2022-12-24
作者：
山東培養(yǎng)基生產(chǎn)
盡管不同的細菌對營養(yǎng)的要求不同，但細菌生長所需要的營養(yǎng)多含有水，碳源，氮源，無機鹽和生長因子。
1，蛋白胨——蛋白胨是制備培養(yǎng)基時最常用的成分之一，提供細菌生長繁殖所需要的氮源。是動物或植物蛋白質(zhì)經(jīng)酶或酸堿分解而成。植物胨和動物胨各有優(yōu)點，配制培養(yǎng)基常將兩者按一定比例混合使用，提高營養(yǎng)價值。蛋白胨易溶于水，遇酸不沉淀，不因受高溫而凝固，并為兩性電解質(zhì)有緩沖作用。但吸水性強，應注意干燥密封保存。
2，肉浸液——是用新鮮牛肉浸泡，煮沸而制成的肉汁。其中含有可溶性含氮浸出物[肌酸，黃嘌呤，腺嘌呤，次黃嘌呤核苷酸，谷氨酸，甘氨酸等]和非含氮浸出物[肝糖，乳酸，琥珀酸，磷酸己糖，脂肪，無機鹽類等]。還有一些生長因子。肉浸液可為細菌提供氮源和碳源，但肉浸液中所含氮物質(zhì)過少而不能滿足細菌的需要，因此在制備培養(yǎng)基時應再加入l%～2%的蛋白胨和0，5%氯化鈉。
3，牛肉膏——由肉浸液經(jīng)長時間加熱濃縮而制成。糖類在加熱過程中被破壞，所以其營養(yǎng)價值低于肉浸液，但因無糖可用作腸道桿菌鑒別培養(yǎng)基的基礎成分。
4，糖類，醇類——為細菌生長提供碳源和能源。制備培養(yǎng)基所用的糖類，醇類有多種，常用的糖類有單糖[葡萄糖，阿拉伯糖等]，雙糖[乳糖，蔗糖等]和多糖[淀粉，菊糖等]；常用的醇類有甘露醇，衛(wèi)茅醇等。除葡萄糖，蔗糖主要作為碳源和能源的基本成分外，其他糖類和醇類主要用于鑒定細菌所做的發(fā)酵反應。
5，血液——血液中既含有蛋白質(zhì)，多種氨基酸，糖類，無機鹽類等營養(yǎng)物質(zhì)，又能提供輔酶[如V因子]，血紅素[X因子]等特殊生長因子，所以在其中加入血液用于培養(yǎng)營養(yǎng)要求較高的細菌。另外，還可根據(jù)細菌在血液培養(yǎng)基中的溶血現(xiàn)象而進行鑒定。
6，無機鹽類——提供細菌生長的各種元素，如鉀，鈉，鐵，鎂，鈣，磷，硫等。用于制備時的無機鹽類有多種，其中最常用的有氯化鈉和磷酸鹽，前者對維持酶的活性，調(diào)節(jié)菌體內(nèi)外的滲透壓非常重要，后者是細菌良好的磷源，并在培養(yǎng)基中具有緩沖作用。
7，雞蛋和動物血清——雖然不是構(gòu)成培養(yǎng)基的基本成分，但卻是某些細菌生長所必需的營養(yǎng)物質(zhì)，所以僅用于制備一些特殊的培養(yǎng)基，這些細菌直接從雞蛋和動物血清中獲取營養(yǎng)。如培養(yǎng)結(jié)核分枝桿菌的雞蛋培養(yǎng)基和培養(yǎng)白喉桿菌的呂氏血清培養(yǎng)基等。
8，生長因子——是細菌生長所必需的，但需要量很小。在制備時，常在肝浸液，肉浸液，酵母浸液和含血液培養(yǎng)基中加入維生素，氨基酸，嘌呤，嘧啶等生長因子。
The components and nutrients of the medium
Although different bacteria have different nutritional requirements, the nutrients needed for bacterial growth include water, carbon, nitrogen, inorganic salts and growth factors.
1 peptone peptone is one of the most commonly used components in the preparation of the medium, providing the nitrogen source needed for the growth and reproduction of bacteria. It is the decomposition of protein from animal or plant by enzyme or acid base. Peptone and animal peptone each have their own advantages. Mixing medium is usually used in a certain proportion to improve the nutritional value of the medium. Peptone is soluble in water, does not precipitate when it is acid, does not solidify due to high temperature, and has buffering effect on amphoteric electrolyte. But the water absorbability is strong, we should pay attention to the dry seal and preservation.
2, meat extract is made from fresh beef and boiled. It contains soluble nitrogen extract [creatine, xanthine, adenine, hypoxanthine nucleotide, glutamic acid, glycine, etc.] and non nitrogenous extracts [liver sugar, lactic acid, succinic acid, hexose phosphate, fat, inorganic salts, etc.]. There are also some growth factors. Meat extract can provide nitrogen source and carbon source for bacteria, but the nitrogen substance in the meat extract is too small to meet the needs of bacteria. Therefore, l% - 2% peptone and 0, 5% sodium chloride should be added to the preparation medium.
3, beef paste is made from meat infusion by heating and concentrating over a long period of time. The sugar is destroyed during heating, so its nutritive value is lower than that of meat extract. However, sugar free can be used as the basic ingredient of identification medium for Enterobacteriaceae. Because of its convenient use, it is often used in the preparation of medium.
4, carbohydrates and alcohols provide carbon sources and energy for bacterial growth. There are many kinds of carbohydrates used in the preparation of culture medium. The commonly used carbohydrates are monosaccharides [glucose, Arabia sugar, etc.], sugar [lactose, sucrose and so on] and polysaccharides [starch, chrysanthemum, etc.]; the commonly used alcohols are mannitol, monosol and so on. In addition to glucose, sucrose is mainly used as the basic component of carbon and energy. Other sugars and alcohols are mainly used to identify fermentation reactions produced by bacteria.
5, blood - the blood contains both protein, various amino acids, carbohydrates, inorganic salts and other nutrients, and also provides coenzyme [such as V factor], heme [X factor] and other special growth factors, so the culture medium is added to the culture of high nutritive bacteria. In addition, it can be identified according to the hemolysis phenomenon of bacteria in blood culture medium.
6, inorganic salts - all kinds of elements that provide bacteria growth, such as potassium, sodium, iron, magnesium, calcium, phosphorus, sulfur, etc. There are many kinds of inorganic salts used in the preparation of medium, the most commonly used are sodium chloride and phosphate. The former is very important to maintain the activity of enzymes and regulate osmotic pressure inside and outside of the bacteria. The latter is a good source of phosphorus and has a buffering effect in the medium.
7, eggs and animal sera, although not the basic components of the medium, are essential nutrients for the growth of some bacteria, so they are used only to prepare some special medium, which directly derive nutrients from eggs and animal serum. For example, the culture medium of Mycobacterium tuberculosis and Luji serum culture medium for diphtheria.
8, growth factors are necessary for bacterial growth, but they are very small. In the preparation of medium, vitamin, amino acid, purine, pyrimidine and other growth factors are often added in liver extract, meat extract, yeast extract and blood culture medium.