The resuscitation promotion concept extends to firmicutes.

Listeria monocytogenes is a facultative pathogenic bacterium that lives in the environment as a saprophyte but can turn into a harmful pathogen affecting humans as well as animals upon ingestion. These bacteria have the remarkable capacity to actively invade eukaryotic host cells, to multiply within them, and to spread to neighbouring cells (Freitag et al., 2009). The transition from an environmental saprophyte to a pathogen is primarily controlled by the transcription factor PrfA. This regulatory protein directly activates the expression of the major virulence genes required for the individual steps of the infection cycle, i.e. invasion, escape from the phagosome, intracellular motility and cell-to-cell spread (de las Heras et al., 2011). Due to its ubiquitous nature, contamination of the food processing chain by L. monocytogenes is a frequent event and leads to repeating listeriosis outbreaks with a high number of severe and even fatal cases (Allerberger & Wagner, 2010). Listeriosis is clearly among the deadliest gastrointestinal bacterial infections as mortality rates of up to 30 % have been reported (Ramaswamy et al., 2007). Consequently, L. monocytogenes has become one of the most comprehensively studied human pathogens (Cossart, 2007, 2011). However, we are still far from a complete understanding of virulence of the well-characterized and sequenced L. monocytogenes strain EGD-e. For example, the function of roughly one-third of all L. monocytogenes EGD-e genes is still unknown according to the KEGG genome database (http://www.genome.jp/dbgetbin/www_bget?genome:T00066).