Expression of a Pseudomonas putida aminotransferase involved in lysine catabolism is induced in the rhizosphere

Using a transposon carrying a promoterless lux operon to generate transcrip tional fusions by insertional mutagenesis, we have identified a Pseudomonas putida gene with increased expression in the presence of corn root exudate s. Expression of the transcriptional fusion, induced by the amino acid lysi ne, was detected in P. putida in the rhizosphere of plants as well as in re sponse to seed exudates. The mutant was unable to grow on lysine or delta - aminovalerate as carbon sources, which indicates that the affected function is involved in the pathway for lysine catabolism. However, the mutant stra in grew with glutaric acid, the product of delta -aminovalerate metabolism via glutaric acid semialdehyde, as a C source. The translated sequence of t he interrupted gene showed high levels of similarity with aminotransferases . These sets of data suggest that the product of this gene has delta -amino valerate aminotransferase activity. This is the first direct genetic eviden ce correlating a DNA sequence with such activity in Pseudomonadaceae.