Vitamin C is an essential water-soluble vitamin in humans, primates and a few other mammals, and is widely used in the pharmaceutical, food, cosmetics, and feed industries for its antioxidant capacity. To achieve large-scale industrial production, the precursor of Vc, 2-keto-L-gulonic acid is mainly produced using a classic two-step fermentation process. In the second step of the two-step fermentation process, the microbial consortium of Ketogulonicigenium vulgare and Bacillus strains is used to achieve 2-KLG production. However, the relationship between the two strains are still unclear.The purpose of our study was to determine cell-cell communication in a microbial consortium consisting of K. vulgare and Bacillus pumilus by iTRAQ-based proteomics.