论述革兰氏染色的机制。 -题库考试答案搜索网

论述革兰氏染色的机制。

论述题

2021-07-18 13:02

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正确答案

(1)革兰氏染色与细菌等电点有关
已知革兰氏阳性菌的等电点为pH为2—3,革兰氏阴性菌的等电点为pH为4—5。革兰氏阳性菌的等电点比革兰氏阴性菌的等电点低,说明革兰氏阳性菌带的负电荷比革兰氏阴性菌多。它与草酸铵结晶紫的结合力大,用碘—碘化钾媒染后,两者的等电点均得到降低,但革兰氏阳性菌的等电点降低得多,故与草酸铵结晶紫结合得更牢固,对乙醇脱色的抵抗力更强。它的菌体与草酸铵结晶紫、碘—碘化钾的复合物不被乙醇提取,呈紫色。而革兰氏阴性菌与草酸铵结晶紫的结合力弱,其菌体与草酸铵结晶紫、碘—碘化钾的复合物很容易被乙醇提取而呈现无色。(5分)

试题解析

(1)革兰氏染色与细菌等电点有关
已知革兰氏阳性菌的等电点为pH为2—3,革兰氏阴性菌的等电点为pH为4—5。革兰氏阳性菌的等电点比革兰氏阴性菌的等电点低,说明革兰氏阳性菌带的负电荷比革兰氏阴性菌多。它与草酸铵结晶紫的结合力大,用碘—碘化钾媒染后,两者的等电点均得到降低,但革兰氏阳性菌的等电点降低得多,故与草酸铵结晶紫结合得更牢固,对乙醇脱色的抵抗力更强。它的菌体与草酸铵结晶紫、碘—碘化钾的复合物不被乙醇提取,呈紫色。而革兰氏阴性菌与草酸铵结晶紫的结合力弱,其菌体与草酸铵结晶紫、碘—碘化钾的复合物很容易被乙醇提取而呈现无色。(5分)

标签：环境工程专升本环境微生物学环境微生物

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