Environmental stress responses inLactococcus lactis

Abstract

Bacteria can encounter a variety of physical conditions during their life. Bacterial cells are able to survive these (often adverse) conditions by the induction of specific or general protection mechanisms. The lactic acid bacterium Lactococcus lactis is widely used for the production of cheese. Before and during this process as well as in its natural habitats, it is subjected to several stressful conditions. Such conditions include oxidation, heating and cooling, acid, high osmolarity/dehydration and starvation. In many environments combinations of these parameters occur. Understanding the stress response behaviour of L. lactis is important to optimize its application in industrial fermentations and is of fundamental interest as L. lactis is a non‐differentiating Gram‐positive bacterium. The stress response mechanisms of L. lactis have drawn increasing attention in recent years. The presence in L. lactis of a number of the conserved systems (e.g. the heat shock proteins) has been confirmed. Some of the regulatory mechanisms responding to an environmental stress condition are related to those found in other Gram‐positive bacteria. Other stress response systems are conserved at the protein level but are under control of mechanisms unique for L. lactis. In a number of cases exposure to a single type of stress provides resistance to other adverse conditions. The unravelling of the underlying regulatory systems gives insight into the development of such cross resistance. Taken together, L. lactis has a unique set of stress response mechanisms, most of which have been identified on the basis of homology with proteins known from other bacteria. A number of the regulatory elements may provide attractive tools for the development of food grade inducible gene expression systems. Here an overview of the growth limits of L. lactis and the molecular characterization of its stress resistance mechanisms is presented.

Gene-Trait Matching and Prevalence of Nisin Tolerance Systems in Lactococus lactis

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Reconstitution of Holin Activity with a Synthetic Peptide Containing the 1–32 Sequence Region of EJh, the EJ-1 Phage Holin

“…This ability makes holins the regulators of both the timing of host lysis and the yield of the phage progeny. Despite the increasing number of holin family members described by genetic analysis and their promising use in biotechnology, their structure and molecular mechanism of action are still unknown (2)(3)(4)(5)(6).…”

Flavescence Dorée Phytoplasma Has Multiple ftsH Genes that Are Differentially Expressed in Plants and Insects

“…A similar role was also suggested for FtsH when B. subtilis was subjected to environmental stress [46,47]. FtsH/HflB was also found to be involved in temperature and salt tolerance in B. subtilis, Lactococcus lactis, and Lactobacillus plantarum through degradation of denatured proteins [46,[48][49][50]. It is possible that either plant or insect response to phytoplasma infection leads to an increase of oxidative stress towards phytoplasma which could, in turn, induce modifications of ftsH expression to enhance protection.…”