Factors Influencing the Production and Further Metabolism of Indole-3-Acetic Acid by Pseudomonas Savastanoi

Abstract

Certain factors which affect production and accumulation of indole-3-acetic acid (IAA) and activity of enzymes associated with its synthesis from L-tryptophan were investigated in Pseudomonas savastanoi. Addition of Ltryptophan to the culture medium enhances the accumulation of IAA by the bacterium. However, both tryptophan oxidative decarboxylase and indoleacetamide hydrolase, which are involved in the conversion of L-tryptophan to IAA, are produced by the bacterium without addition of L-tryptophan to the medium. In a medium containing L-tryptophan, yields of tryptophan oxidative decarboxylase per liter of culture suspension were increased as much as 2-fold.IAA and indole-3-acetamide (JAM) strongly inhibit tryptophan oxidative decarboxylase. IAA up to 6 X 10-3 M did not inhibit indoleacetamide hydrolase. IAA also inhibits uptake of L-tryptophan by whole cells.IAA is converted to its lysine conjugate by the bacterium. During logarithmic phase of growth in a nutrient medium, the specific activities of tryptophan oxidative decarboxylase and indoleacetamide hydrolase were 2-fold greater than that for the system converting IAA to its lysine conjugate. During the stationary growth phase, specific activity of all three enzymes decreased but that for the first two enzymes did so more rapidly than the specific activity of the lysine conjugate synthetase. Accumulation of IAA in culture filtrates is controlled to a large extent by the relative activities of the systems synthesizing and utilizing IAA.Previous studies have shown that the bacterium, Pseudomonas savaslanoi converts L-tryptophan to indole-3-acetic acid (IAA) in two steps. In the first reaction catalyzed by tryptophan oxidative decarboxylase, L-tryptophan is converted to indole-3-acetamide (TAM). In the second reaction, catalyzed by

Indoleacetic acid operon of Pseudomonas syringae subsp. savastanoi: transcription analysis and promoter identification

“…savastanoi PB213. Analagous constitutive in previous studies (24,36) supports this conclusion. Our experiments did not address whether expression of iaa genes differ when P. syringae subsp.…”

“…The availability of exogenous tryptophan can dramatically increase the yield of IAA from a-P. syringae subsp. savastanoi culture without significantly altering tryptophan monooxygenase activity (24) and without requiring an increase in transcription of iaaM and iaaH. The conversion of IAA to an amino acid conjugate, IAA-lysine, in some P. syringae subsp.…”

Metabolism of Tryptophan by Pseudomonas aureofaciens and Its Relationship to Pyrrolnitrin Biosynthesis

“…A novel tryptophan-metabolizing enzyme, indolyl-3-alkane a-hydroxylase, was isolated from P. JEuorescens ATCC 29574 (Roberts & Rosenfeld, 1977), but neither this enzyme nor tryptophanase could be detected in P. aureofaciens. The indole-3-acetic acid pathway In P. aureofaciens a further pathway of tryptophan metabolism is available in synthesizing the phytohormone indole-3-acetic acid, which is also produced by the phytopathogenic species P. syringae (P. savastanoi) (Kuo & Kosuge, 1969). In plants there are several pathways leading from tryptophan to indole-3-acetic acid : the tryptamine pathway, the indole-3-acetaldoxime pathway, the tryptophol pathway and the indole-3-pyruvate pathway (Schneider & Wightman, 1974).…”

Role of Aminotransferase and Indole-3-Pyruvic Acid in the Synthesis of Indole-3-Acetic Acid in Pseudomonas Savastanoi

“…Indole-3-acetamide hydrolase was assayed by the procedure of KUo and KOSUGE (4). A unit of hyrolase activity is defined as that amount catalyzing the formation of 1 mp mole of IAA per minute under standard assay condition (4).…”