The phage shock protein response of Listeria monocytogenes influences tolerance to the multipeptide bacteriocin garvicin KS

An estimated 30% of all food produced worldwide is lost or wasted every year. A considerable portion of that waste is due to perishable food products, that spoil and can become unsafe to eat relatively quickly. For some high-quality perishables, such as fresh fish and cold-smoked salmon, traditional food preservation techniques are unsuitable as they can compromise sensory qualities such as flavor, texture, and freshness. These products often support the growth of the human pathogen Listeria monocytogenes, which can be present if thermal treatment is not applied. Thus, antilisterial bacteriocins like garvicin KS (GarKS) in combination with conventional technologies like high-pressure processing (HPP) or modified atmosphere packaging (MAP) are being investigated as hurdle strategies to increase the shelf life and food safety of packaged fish products. In this study we showed that L. monocytogenes strains associated with fish food and fish processing plants are susceptible to GarKS with MIC values ranging from 20 to 275 nM. Exposure to GarKS resulted in an upregulation of genes involved in the phage shock protein response, and isolation of resistant mutants indicated a low frequency of resistance to GarKS (10{square}{square} to 10{square}11). Resistant mutants were shown to harbor disruption mutations in lmo2468, encoding a PspC-domain-containing protein. Overexpression of this gene increased susceptibility to GarKS two-fold and restored wild-type susceptibility in a disruption mutant. This study identify the phage shock protein response as a key player involved in susceptibility to GarKS.