Octopine and octopinic acid utilization in a nonfluorescent Pseudomonas sp.: enhancement by spontaneous mutation and lack of effect from curing of a plasmid

Abstract

An octopine-utilizing bacterium isolated from soil, named strain 92, was identified to the genus level as a nonfluorescent Pseudomonas. Utilization of octopine by strain 92 depended upon the presence of an alternative carbon source, while octopinic acid was not utilized. A mutant derivative, strain RB100, acquired simultaneously the capacity to utilize octopine as the sole carbon and nitrogen source and octopinic acid as the nitrogen source. The mutation rate was estimated to be about 10−8 per cell per generation. Both the wild type and mutant carried the 68.5-kilobase cryptic plasmid pDLB 1. When the plasmid present in strain RB100 was labelled with Tn5 and transferred to strain 92, the phenotype of the recipient was not modified with respect to octopine utilization, suggesting that this phenotype was not determined by pDLB1. This suggestion was confirmed by using unstable derivatives of pDLB1 to cure strain RB100 and showing that the cured strain was not affected in its capacity to utilize opines.