Complementation of Listeria seeligeri with the plcA-prfA genes from L-monocytogenes activates transcription of seeligerolysin and leads to bacterial escape from the phagosome of infected mammalian cells

Infection experiments have shown that the avirulent species Listeria seeligeri invaded the enterocyte-like cell line Caco-2 with low efficiency but was unable to escape from the phagosome. Introduction of the listeriolysin gene (hly) from L. monocytogenes into L. seeligeri via a recombinant plasmid did not change these characteristics. No measurable transcription of this gene or of the structurally intact chromosomal seeligerolysin gene (lso) was detected. Transformation with a plasmid carrying the bicistronically transcribed plcA-prfA genes from L. monocytogenes resulted in the efficient expression of the plasmid-encoded transcription activator PrfA, a readily detectable synthesis of seeligerolysin and the escape of the bacteria from the phagosome of infected mammalian cells, followed by intracytoplasmic multiplication.