Sourdoughs are complex ecosystems which are widely used to produce baked goods. This study aimed to provide a dynamic description of an industrial French sourdough ecosystem over 10 consecutive days. The sourdough was obtained from a natural fermentation that has been propagated over several years by the traditional backslopping method. The physico-chemical properties (pH, temperature, total titratable acidity) and the diversity of the lactobacilli among the microbiota were analyzed. A culture-dependent approach provided genotypic (REP-PCR) and phenotypic characterizations. The ecosystem showed a cyclic dynamic. The pH ranged from 3.41 to 3.7 and the acidity levels from 13.9 to 22.4 ml NaOH. A stable lactobacilli microbiota was observed in the sourdough over the 10 days. It was composed of four predominant species assigned to Lactobacillus panis, Lactobacillus frumenti, Lactobacillus amylolyticus and Lactobacillus acetotolerans. The phenotypic tests highlighted an acidification function for the Lb. amylolyticus and Lb. acetotolerans populations, whereas the Lb. panis and Lb. frumenti populations seemed more aromatic. Therefore, this natural sourdough was composed of an atypical microbial association.