Synthesis of listeriolysin in Listeria monocytogenes under heat shock conditions.

Listeriolysin, produced by all virulent Listeria monocytogenes isolates, is an essential virulence factor which appears to be necessary for the intracellular survival of these bacteria. It has been postulated that the intracellular environment imposes stress conditions similar to heat shock on invading bacteria. We show here that listeriolysin was still very efficiently synthesized in one Listeria monocytogenes strain even intracellularly and induced under heat shock conditions in another L. monocytogenes strain. Listeriolysin appears to be the only major extracellular protein synthesized under heat shock conditions; all other heat shock proteins remain cell associated.