Stress response assessment ofLactobacillus sakeistrains selected as potential autochthonous starter cultures by flow cytometry and nucleic acid double-staining analyses

Aims:The aim of this study was to apply the flow cytometry toLactobacillus sakei strains, selected as potential autochthonous starters, to investigate dynamics and physiological heterogeneity of microbial behaviour under different stress conditions. Methods and Results:A simultaneous nucleic acid double-staining assay was applied to discriminate cell populations in different physiological states after exposure to heat (50 and 55°C) and acid (pH 25 and 30) stresses. Alive cells with intact membranes, damaged cells still alive but with injured membranes, so with even a recovery ability, and dead cells with a permanent membrane damage were differentiated with a significant increase in damaged cells after stronger stress treatments. Conclusions:The existence and characteristics of subpopulations displaying heterogeneity in particular conditions are highly relevant, because specific subpopulations may show improved survival, changes and dynamics under stress condition