Molecular mechanisms of stress resistance in Lactococcus lactis

Lactococcus is an economically important starter culture bacterium extensively used in the manufacture of the both soft and hard cheeses. During its growth and storage, and throughout cheese processing, it encounters a variety of stresses including osmotic, oxidative, temperature, acid and cell envelope stress. These stressors can cause damage to DNA, proteins, lipid membranes and peptidoglycan and can lead to reduced growth and acidification rates and if severe enough, cell death. Despite its small genome (~2.5Mbp) Lactococcus is equipped to withstand stress through a number of specific and non-specific mechanisms. Genes involved in stress resistance and/or responding to stress have been identified using a variety of approaches including site-directed mutagenesis, random mutagenesis, microarrays, proteomics and bioinformatic methods. Further research utilising current and novel methods will yield a better understanding of how Lactococcus deals with stress and lead to innovations in industrial fermentation processes.