Characterization of sourdough lactic acid bacteria based on genotypic and cell-wall protein analyses

Aims: To evaluate the effectiveness of two independent methods in differentiating a large population of lactic acid bacteria (LAB) isolated from wheat flours and sourdoughs and to correlate eventual differences/similarities among strains with their geographical origin and/or process parameters. Methods and Results: One hundred fifty strains belonging to Lactobacillus spp. and Weissella spp., plus eight type strains, one for each species, and two unidentified isolates, were characterized by randomly amplified polymorphic DNA (RAPD) and SDS-PAGE of cell-wall proteins. The RAPD analysis separated the eight type strains but did not always assign all the strains of a species to the same group, while SDS-PAGE cell-wall protein profiles were species-specific. Frequently, strains isolated from sourdoughs of the same geographical origin or produced by similar raw material/process parameters showed similar RAPD and/or cell-wall profiles. Conclusions: The combined use of the RAPD and cell-wall protein analysis represents a useful tool to classify large adventitious microbial populations and to discriminate the diversity of the strains. Significance and Impact of the Study: This study represents a typing of a large collection of flour/sourdough LAB and provides evidence of the advantage of using two independent methods in the classification and traceability of microorganisms.