Global genome and comparative transcriptomic analysis reveal the inulin consumption strategy of Lactiplantibacillus plantarum QS7T

• L. plantarum QS7T from Sichuan pickle grew very well on inulin as a carbon source. • L. plantarum QS7T metabolized both short-chain and long-chain inulin components. • A high percentage of genes associated with carbohydrate metabolism were predicted. • The sacPTS1 and fos operons were related to two inulin-consuming strategies. Sichuan pickle is a natural combination of probiotics and dietary fibers, in which a strain Lactiplantibacillus plantarum QS7T was found to be capable of efficiently metabolizing inulin. However, the underlying molecular mechanism of inulin consumption by the strain QS7T is unclear. Therefore, this study firstly investigated the metabolic characteristics of inulin in the strain QS7T, and the results showed it could grow very well on the medium containing inulin as a carbon source (maximum OD 600 nm , 1.891 ± 0.028) and degrade both short-chain oligofructose and long-chain fructan components through thin layer chromatography analysis. Genomic sequencing and analysis revealed a high percentage of functional genes associated with carbohydrate transport and metabolism, particularly glycoside hydrolase (GH) genes responsible for hydrolysing carbohydrates, within the genome of the strain QS7T. Furthermore, comparative transcriptomic analysis of L. plantarum QS7T in response to inulin or glucose indicated that functional genes associated with inulin consumption including several genes encoding PTS sugar transporters and two predicted GH32 family genes encoding beta-fructofuranosidase and beta-fructosidase were significantly up-regulated by inulin compared to the gene expression on glucose. In conclusion, we obtained a mechanistic understanding of interplay between probiotic L. plantarum QS7T derived from Sichuan pickle and natural dietary fiber, inulin; totally two operons including a sacPTS1 operon responsible for metabolizing short-chain oligofructose primarily in the cytoplasm and a fos operon responsible for extracellularly degrading all moderate and long-chain fructan components linked to inulin consumption by L. plantarum QS7T.