Dietary nitrate, mainly found in green-leafy vegetables, is sequentially reduced to nitrite in the oral cavity and to nitric oxide in the stomach. Here, nitric oxide increases mucosal blood flow, mucus thickness and prevents microbial infections. Gut microbiota is now recognized as a pleiotropic organism essential to maintain gastrointestinal (GI) and systemic welfare; indeed, dysbiosis has been associated with increased epithelial permeability and with the activation of inflammatory pathways. Such physiological disturbances are likely to elicit GI symptoms, such as heartburn, dyspepsia and diarrhea during antibiotherapy. Herein, we investigated the impact of nitrate on gut microbiome profile and ensued mucosal effects during dysbiosis. All animal experiments were performed according to the ARRIVE guidelines and the European Community Council Directive for the Care and Use of Laboratory Animals (86/609/ECC). Male Wistar rats (n=32) were used in this study. Animals were randomly distributed in 4 groups (n=8, per group) and the drinking water was supplemented for 7 days as follows: 1) antibiotic cocktail (neomycin 5 mg/mL, bacitracin 5 mg/mL, imipenem 1.25 μg/mL), 2) antibiotic cocktail + sodium nitrate (10 mM), 3) sodium nitrate and 4) control (no supplementation). Animals were weighted daily and feces were collected before and after the treatment. Animals were anesthetized (halothane) and euthanized by cervical dislocation. Ceca were collected and weighted. The stomach and ascending colon were isolated and occludin, claudin-5, -15 as well as myeloperoxidase (MPO) and iNOS were analyzed. Bacterial DNA was analyzed in fecal samples by DGGE. Values are mean±SEM. Nitrate prevented antibiotic-induced body weight loss (1.9±1.8 vs 8.7±1.8, % of increase in respect to day 0, p<0.05) and cecamegalia (7.1±0.5 vs 5.6±0.4, % of total body weight, p<0.05), likely through a more efficient harvesting of nutrients and preserved motility. Gastric expression of occludin and claudin-5 was decreased during dysbiosis, but both protein levels were recovered by nitrate (p<0.05). Similarly, nitrate inhibited MPO and iNOS overexpression under dysbiosis (p<0.05) in the rat stomach. In the large intestine, nitrate increased claudin-5 expression under dysbiosis (p<0.01) but had the opposite effect on occludin (p<0.001). Microbial richness was highly decreased by the antibiotic cocktail but the group also exposed to nitrate showed similarities in specific bacterial groups in comparison to control animals. This data supports that dietary nitrate may be envisaged as a functional food with a beneficial impact on gastric mucosal integrity and microbial profile during dysbiosis and therefore its consumption may be useful throughout antibiotherapy.