Group of bacterial proteins containing an alpha crystallin domain (ACD) similar to Lactobacillus plantarum (Lp) small heat shock proteins (sHsp) HSP 18.5, HSP 18.55 and HSP 19.3. sHsps are molecular chaperones that suppress protein aggregation and protect against cell stress, and are generally active as large oligomers consisting of multiple subunits. Transcription of the genes encoding Lp HSP 18.5, 18.55 and 19.3 is regulated by a variety of stresses including heat, cold and ethanol. Early growing L. plantarum cells contain elevated levels of these mRNAs which rapidly fall of as the cells enter stationary phase. Also belonging to this group is Bifidobacterium breve (Bb) HSP20 and Oenococcus oenis (syn. Leuconostoc oenos) (Oo) HSP18. Transcription of the gene encoding BbHSP20 is strongly induced following heat or osmotic shock, and that of the gene encoding OoHSP18 following heat, ethanol or acid shock. OoHSP18 is peripherally associated with the cytoplasmic membrane.