Reliable use of green fluorescent protein in fluorescent pseudomonads

When fluorescent pseudomonads are cultured on standard solid media under ir on limiting conditions, they produce fluorescent, pigmented iron collating agents (siderophores). Siderophores can be readily identified by strong flu orescence seen under UV/blue light. The application of the eukaryotic green fluorescent protein (GFP) as a bacterial marker in microbial ecology is in creasingly being used, particularly as it is a powerful method for non-dest ructive monitoring in situ. As gfp expressing bacteria have to be detected under UV/blue light, the fluorescence of siderophore-producing Pseudomonas spp. masks normal levels of GFP fluorescence when colonies are viewed on st andard bacterial agar. Here, we describe a simple but effective way of iden tifying gfp-expressing Pseudomonas fluorescens using media supplemented wit h 0.45 mM FeSO4. 7H(2)O. This is of relevance for the screening of insertio n libraries and in the application of GFP transposons as promoter probes. ( C) 2001 Elsevier Science B.V. All rights reserved.