CONSTRUCTION OF A MODIFIED MINI-TN5 LACZY NON-ANTIBIOTIC MARKER CASSETTE - ECOLOGICAL EVALUATION OF A LACZY MARKED PSEUDOMONAS STRAIN IN THE SUGAR-BEET RHIZOSPHERE

In order to monitor the fate of genetically manipulated fluorescent ps eudomonads following release into the environment, a lacZY transposabl e cassette, lacking antibiotic resistance genes, was constructed using a pUT suicide plasmid delivery system. The resulting plasmid, pUTLacZ Y, can be easily used to generate lacZY marked pseudomonads without ha ving to use antibiotic resistance determinants. The lacZY transposon g enerates random, stable transcriptional/translational fusions on integ ration into the target genome. Pseudomonas fluorescens strain F113 was marked with lacZY and was unaltered with respect to ecological fitnes s in the rhizosphere. Although lateral gene transfer of the chromosoma lly integrated lacZY marker could be detected in vitro, it was not det ected in rhizosphere microcosms.