荧光假单胞菌
色氨酸
拉伤
生物化学
吲哚-3-乙酸
氧化酶试验
化学
假单胞菌
吲哚试验
生物
生长素
酶
细菌
氨基酸
解剖
基因
遗传学
作者
Thomas Oberhänsli,Genèvieve Défago,Dieter Haas
出处
期刊:Journal of General Microbiology
[Microbiology Society]
日期:1991-10-01
卷期号:137 (10): 2273-2279
被引量:116
标识
DOI:10.1099/00221287-137-10-2273
摘要
Pseudomonas fluorescens strain CHA0 is an effective biocontrol agent against soil-borne fungal plant pathogens. In this study, indole-3-acetic acid (IAA) biosynthesis in strain CHA0 was investigated. Two key enzyme activities were found to be involved: tryptophan side chain oxidase (TSO) and tryptophan transaminase. TSO was induced in the stationary growth phase. By fractionation of a cell extract of strain CHA0 on DEAE-Sepharose, two distinct peaks of constitutive tryptophan transaminase activity were detected. A pathway leading from tryptophan to IAA via indole-3-acetamide, which occurs in Pseudomonas syringae subsp. savastanoi, was not present in strain CHA0. IAA synthesis accounted for ⩽1·5% of exogenous tryptophan consumed by resting cells of strain CHA0, indicating that the bulk of tryptophan was catabolized via yet another pathway involving anthranilic acid as an intermediate. Strain CHA750, a mutant lacking TSO activity, was obtained after Tn5 mutagenesis of strain CHA0. In liquid cultures (pH 6·8) supplemented with 10 mm-l-tryptophan, growing cells of strains CHA0 and CHA750 synthesized the same amount of IAA, presumably using the tryptophan transaminase pathway. In contrast, resting cells of strain CHA750 produced five times less IAA in a buffer (pH 6·0) containing 1 mm-l-tryptophan than did resting cells of the wild-type, illustrating the major contribution of TSO to IAA synthesis under these conditions. In artificial soils at pH ~7 or pH ~6, both strains had similar abilities to suppress take-all disease of wheat or black root rot of tobacco. This suggests that TSO-dependent IAA synthesis is not essential for disease suppression.
科研通智能强力驱动
Strongly Powered by AbleSci AI