Increasing membrane protection in Lactobacillus plantarum cells overproducing small heat shock proteins.

We have investigated a potential link between small heat shock proteins (sHsps) and membranes in Lactobacillus plantarum WCFS1. The sHsp family is the best characterized protein subset among the L. plantarum Hsps, and it represents the principal heat shock regulon of Gram-positive bacteria in this bacterium. Exposure to benzylic alcohol (BA) (60 mM) alone was found to cause membrane fluidization in the absence of any other stress and to induce transcription of the heat shock genes (shs) to the same extent as a lethal heat shock. Using a fluorescence anisotropy-based method, we detected a reduction in the maximal fluidification level in two L. plantarum strains that singly over-produce Hsp18.5 and Hsp19.3. Overall, these results indicate that, under the stress conditions analysed, these two members of the sHsps family of L. plantarum WCFS1 have a membraneactivating effect. The findings also form a basis for proposing membrane fluidity as a new target for prestress treatments to enhance probiotic, food starter and bioproduction applications of L. plantarum.