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 extr...

Plasmids are a main factor for the evolution of bacteria through horizontal gene exchange, including the dissemination of pathogenicity genes, resistance to antibiotics and degradation of pollutants. Their capacity to duplicate is dependent on their replication determinants (replicon), which also define their bacterial host range and the inability to coexist with related replicons. We character...

A polymerase chain reaction (PCR) protocol that can be used to distinguish Pseudomonas syringae pv. tagetis from other P. syringae pathovars, including those that induce apical chlorosis in several plants of the Asteracaea family and in pea, and closely related P. savastanoi pathovars was developed based on DNA sequences from P. syringae pv. tagetis that are required for tagetitoxin synthesis. ...

An enzyme which catalyzes the conversion of L-tryptophan to indole-3-acetamide has been isolated from cells of Pseudomonas savastanoi and purified 89-fold. The enzyme catalyzes a reaction in which 1 mole of L-tryptophan and 1 mole of 02 are consumed and 1 mole of indole-3-acetamide and 1 mole of CO2 are produced. The enzyme has a pH optimum between 7.2 and 9.2. It is specific for the L isomer o...

We have developed a new assay that differentiates between indoleacetic acid (IAA)-producing and -nonproducing bacteria on a colony plate lift. Medium supplemented with 5 mM L-tryptophan is inoculated with isolates of interest, overlaid with a nitrocellulose membrane, and then incubated until bacterial colonies reach 1 to 2 mm in diameter. The membrane is removed to a filter paper saturated with...