Protein Profile and Plasmid Content of Lactococcus lactis subsp. lactis LL52 and Lactococcus lactis subsp. cremoris LC79 Strains under Several Stress Conditions

Differences in the protein and plasmid content of 2 Lactococcus lactis strains, L. lactis subsp. lactis LL52 and L. lactis subsp. cremoris LC79, under the stresses of high and low temperature, osmotic shock, and low pH were determined. We identified 3 new proteins with molecular masses of 16.0, 29.4, and 45.0 kDa as high temperature stress response specific in strain LL52. High temperature stress did not cause any changes in the protein content of strain LC79. Proteins that were specific for salt stress and low pH stress responses ranged between 16.0 and 40.5 kDa, and 24.8 and 107.5 kDa, respectively, in both strains. No proteins were related to low temperature stress in LL52 and LC79 strains. Plasmid analysis indicated that there was no relationship between stress responses and plasmids in these bacteria.