Bi-functional gfp-and gusA-containing mini-Tn5 transposon derivatives for combined gene expression and bacterial localization studies

The gfp gene, encoding the green fluorescent protein, was combined with the gusA gene, coding for the beta-glucuronidase enzyme, in mini-Tn5 transposo n derivatives for use in Gram-negative bacteria. These mini-Tn5 elements al low simultaneously monitoring of gene expression and localization of the ma rked bacteria. Introduction of the resultant mini-Tn5 transposons into Rhiz obium etli, Azospirillum brasilense and Pseudomonas stutzeri allowed us to visualise the interaction of these bacteria with their host plant. The dual -marker mini-Tn5 transposons constitute a powerful new tool for studying ge ne expression and ecology of bacteria in the environment and during the int eraction with plants. (C) 1999 Elsevier Science B.V. All rights reserved.