Threonine metabolism by Pseudomonas aeruginosa.

83 strains of Pseudomonas aeruginosa were unable to utilize l-threonine as carbon-energy source, although this compound served as sole nitrogen source. Auxotrophs of P. aeruginosa 9-D2 that required l-serine or glycine for growth could grow in the presence of l-threonine. Extracts of P. aeruginosa 9-D2 grown in the presence of l-threonine contained threonine dehydrogenase and alpha-amino beta-ketobutyrate: CoA ligase activities; threonine aldolase was not detectable. Cells grown in the absence of l-threonine produced no detectable threonine dehydrogenase. l-Leucine neither stimulated nor repressed threonine dehydrogenase levels. Glycine, and to a lesser extent l-serine, repressed l-threonine-mediated threonine dehydrogenase synthesis. A mutant of strain 9-D2 was isolated that could utilize l-threonine as sole carbon-energy source. This strain produced elevated levels of threonine dehydrogenase, but only slightly higher levels of alpha-amino beta-ketobutyrate: CoA ligase activities. [ABSTRACT FROM AUTHOR]