AcrR and Rex Control Mannitol and Sorbitol Utilization through Their Cross-Regulation of Aldehyde-Alcohol Dehydrogenase (AdhE) in Lactobacillus plantarum.

is a versatile bacterium that occupies a wide range of environmental niches. In this study, we found that a bifunctional aldehyde-alcohol dehydrogenase-encoding gene, , was responsible for being able to utilize mannitol and sorbitol through cross-regulation by two DNA-binding regulators. In NF92, was greatly induced, and the growth of an -disrupted () strain was repressed when sorbitol or mannitol instead of glucose was used as a carbon source. The results of enzyme activity and metabolite assays demonstrated that AdhE could catalyze the synthesis of ethanol in NF92 when sorbitol or mannitol was used as the carbon source. AcrR and Rex were two transcriptional factors screened by an affinity isolation method and verified to regulate the expression of DNase I footprinting assay results showed that they shared a binding site (GTTCATTAATGAAC) in the promoter. Overexpression and knockout of AcrR showed that AcrR was a novel regulator to promote the transcription of The activator AcrR and repressor Rex may cross-regulate when NF92 utilizes sorbitol or mannitol. Thus, a model of the control of by AcrR and Rex during NF92 utilization of mannitol or sorbitol was proposed. The function and regulation of AdhE in the important probiotic genus are rarely reported. Here we demonstrated that AdhE is responsible for sorbitol and mannitol utilization and is cross-regulated by two transcriptional regulators in NF92, which had not been reported previously. This is important for to compete and survive in some harsh environments in which sorbitol or mannitol could be used as carbon source. A novel transcriptional regulator AcrR was identified to be important to promote the expression of , which was unknown before. The cross-regulation of by AcrR and Rex is important to balance the level of NADH in the cell during sorbitol or mannitol utilization.