THE GREEN FLUORESCENT PROTEIN AS A VISIBLE MARKER FOR LACTIC-ACID BACTERIA IN COMPLEX ECOSYSTEMS

The potential of the gfp (green fluorescent protein) gene from the jel lyfish Aequoria victoria as a visible marker for tracking lactic acid bacteria introduced into complex anaerobic ecosystems was examined. A red-shifted mutant gfp gene was placed downstream of the constitutive Lactococcus lactis P32 promoter and fluorescence resulting from green fluorescent protein (GFP) expression was detected in Escherichia coil and L. lactis. The construct (pKPSPsgfp) was also introduced into Ente rococcus faecalis, Streptococcus gordonii and Streptococcus bovis by m obilisation with pVA797. In all cases fluorescence was detectable at t he level of individual cells, and isolated colonies, Although oxygen i s required for GFP to fluoresce, colonies or cells grown anaerobically were able to fluoresce upon subsequent exposure to air. A combination of selective plating and colony fluorescence allowed a gfp marked str ain of E. faecalis to be enumerated after addition to an anaerobic con tinuous culture of human faecal flora. (C) 1998 Federation of European Microbiological Societies, Published by Elsevier Science B.V. All rig hts reserved.