Autofluorescence and green fluorescent protein-derived fluorescence in Listeria innocua

摘要

Fluorescent L. innocua Ml was generated by transformation with plasmid SB2019 carrying gfp3. The transformed organism exhibited 2 h longer lag phase than the parental strain. The transformation and gfp3 expression did not affect the growth rates (0.49+- 0.02 and 0.47 +- 0.05 h~(-1)) and the maximum optical densities (1.02 +- 0.01 and 0.90 +- 0.06) of the parental or the transformed strains. The transformation of L. innocua Ml with pSB2019 resulted in cell-concentration related fluorescence which was detectable from washed cells but not in growth media. Statistical discrimination between GFP3-driven and background fluorescence signals of transformed and parental strains occurred at cell optical densities of 0.1 and above which was partiallydue to a relatively high endogenous autofluorescence. Although the g/p-trans-formed L. innocua Ml developed in this study has the potential to be a marker organism for monitoring Listeria spp. responses in mixed cultures, more work is needed to optimizethe GFP-based fluorescent signal.