Due to the excellent probiotics, Lactobacillus plantarum was widely used in the field of fermentation food, feed, and medicine. However, genetic information and physiological metabolism of L. plantarum were rarely reported. In order to explore the molecular mechanism of physiological characteristics and metabolic pathways of L. plantarum, and explore the functional genes related to important traits, the strain L. plantarum DY6 with fast growth rate, strong acid production ability, and rich metabolites was selected as the research object in this study. The molecular mechanism of physiological characteristics of L. plantarum DY6 was revealed by comparing the physiological characteristics and genetic information with L. plantarum WCFS1. Compared with L. plantarum WCFS1, L. plantarum DY6 had significant advantages in growth activity, sugar acid conversion rate, carbon source metabolism, and amino acid metabolism, mainly including glucose, fructose and galactose metabolism, arginine and aspartate metabolism. Genome re-sequencing obtained 19 396 single nucleotide polymorphisms, 972 insertion or deletion mutations, and 4331 annotated mutation genes. There were 102 mutations in metabolic pathways that were significantly different from pyruvate metabolism, carbohydrate metabolism and amino acid metabolism. Analyzing the metabolic characteristics and genome differential between L. plantarum WCFS1 and L. plantarum DY6, we speculated that the following changes possibly existed in L. plantarum DY6: (1) beneficial mutations existed in the PTS system, resulting in enhanced transportability for carbohydrates, promoting the cell growth; (2) fructokinase, fructose specificity EIIABC (fruA) and EIIBC (PTS31BC) possibly had higher activity, enhancing the metabolic flux from fructose to lactic acid; (3) phosphofructokinase (fruK) and L-lactate dehydrogenase (ldhl2) probably had higher activity, enhancing the transformation of glucose and pyruvic acid to glycolysis pathway and lactic acid, respectively; (4) harmful mutations possibly existed in metK and/or mtn, restricted the methionine metabolic pathway, resulting in the low consumption rates; (5) gadB possibly contained harmful mutations, influencing the biosynthesis of γ-aminobutyric acid and acid resistance; (6) mutations in argF resulted a faster consumption rates of arginine. On this basis, the transcription levels of key genes directly related to pyruvate metabolism were determined. It was found that the relative expression levels of pdhC, ack1, and Idhl2 in L. plantarum DY6 were 20, 15, and 14 times higher than those in L. plantarum WCFS1, respectively. It was speculated that the change of these gene sequences probably had an important impact on the functional differences, which laid a theoretical foundation for further understanding the molecular mechanisms related to L. plantarum fermentation and probiotic characteristics.
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