Transcriptomic Responses to Nitrite Degradation by RC4 and Effect of Gene Overexpression on Nitrite Degradation.

The excessive nitrite residue may increase cell damage and cancer risk. RC4 exhibited excellent nitrite degradation ability. Herein, the molecular mechanism of nitrite degradation by RC4 was studied by integrating scanning electron microscopy analysis, transcriptomics, and gene overexpression. The results demonstrated that the gene profile of RC4 cultured in MRS broth with 0, 100, and 300 mg/L NaNO varied considerably; RC4 responded to nitrite degradation by regulating pyruvate metabolism, energy synthesis, nitrite metabolism, redox equilibrium, protein protection, and signaling. High nitrite concentrations affected the morphology of RC4 with a longer phenotype, rough and wrinkle cell and reduced cell surface hydrophobicity. Moreover, an up-regulated expression of gene encoding NADH dehydrogenase, which provides electrons for nitrite reduction by catalyzing NADH, was identified when RC4 was exposed to nitrite. Overexpression of in RC4 increased the nitrite degradation rate by 2-9.5% in MRS broth with 100 mg/L NaNO. Thus, the findings of this study could be helpful for the application of to reduce nitrite residues and improve food safety in fermented food products.