粪产碱菌的Tn5转座诱变及吲哚乙酸生物合成特性的研究

TN5 MUTAGENESIS AND THE CHARACTERISTICS OF INDOLE-3-ACETIC ACID BIOSYNTHESIS IN ALCALIGENES FAECALIS A1501

粪产碱菌 (Alcaligenesfaecalis)A1 50 1的吲哚乙酸 (IAA)合成需要外源色氨酸参与。在不含色氨酸的限制性培养基中 ,A1 50 1能良好生长 ,但不能合成IAA ,表明在A1 50 1中存在一条依赖于色氨酸的IAA合成途径。A1 50 1的IAA合成具有菌体密度依赖特性。采用Tn5转座诱变技术构建A1 50 1的突变库 ,从 350 0多株Tn5转染子中分离到一株色氨酸营养缺陷型突变株AT63。该Tn5突变株在不含色氨酸的限制性培养基上不能生长 ,但仍能进行IAA的生物合成 ,每毫升菌体密度等于 1 0的突变株菌体的IAA合成量为 2 2 4 μg。对突变株AT63的研究表明在A1 50 1中至少存在两条IAA合成途径 :一条以色氨酸为合成前体 ,另一条以吲哚 - 3-磷酸甘油为前体。southern杂交结果表明突变株中Tn5插入位点可能位于编码色氨酸合成酶基因上。

The IAA production of Alcaligenes faecalis wild type strain A1501 depended on addition of L\|tryptopham(trp).A1501 could grow well in minimal medium without Trp,but could not produce IAA.The results indicated that there was Trp\|dependent IAA biosynthesis pathway in A.faecalis A1501.A1501 shows a characteristic of cell density\|dependent IAA biosynthesis.The Tn5\|induced mutant bank of A1501 was constructed using Tn5 mutagensis and one Trp auxotrophic mutant AT63 was selected and identified.The Tn5\|induced mutant AT63 could synthesis 2.24μg/mL IAA in minimal medium without L\|Trp.It indicated there were at least two IAA biosynthesis pathways in A.faecalis,one needed Trp,the other needed IGP as precursor.The results of southern hybridization also suggested that the Tn5\|insertion might locate in gene locus encoded IAA synthetase.