| Leuconostoc mesenteroides is a Gram-positive bacteria with special fermentation commonly used in natural fermented milk and pickled cabbage,and is one of the important lactic acid bacteria strains.Due to its excellent extracellular polysaccharide and bacteriocin production capacity and acid production characteristics,it is often used as a starter in the food industry.At present,most of the studies have focused on the screening of Leuconostoc mesenteroides with excellent characteristics,and its further development and utilization are limited by the lack of research on genetic diversity and functional genomics.Systematic analysis of genetic diversity and functional genomic characteristics of Leuconostoc mesenteroides is of great significance for the development and utilization of Leuconostoc mesenteroides.Relying on the Lactic Acid Bacteria Collection Center of Inner Mongolia Agricultural University,the whole genome of 80 strains of naturally fermented dairy products isolated from Chinese Inner Mongolia Autonomous Region,Sichuan Province,Gansu Province,and Xinjiang Uyghur Autonomous Region was sequenced using Illumina Novaseq high-throughput sequencing platform in this study.In combination with the whole genome sequences of 98 Leuconostoc mesenteroides published by NCBI,population genetics and functional genomics analysis were performed,and the results were as follows:(1)The genome size of 178 Leuconostoc mesenteroides strain was 1.92±0.15 Mb,and that GC content was 37.75±0.20%.It constructs its core gene-pangene set,and its pangenome belongs to open genome.Population recombination rate is low.(2)A phylogenetic tree was constructed based on 735 core genes for analysis.The results showed that 178 Leuconostoc mesenteroides strains could be divided into four branches,and their genetic evolution was related to the geographical origin and the geographical separation.The isolates from Sichuan and Gansu regions had a close genetic relationship.The ANOVA analysis of the genomic characteristics of the strain and environmental factors revealed that the basic characteristics of the strain differed significantly in different environments.Leuconostoc mesenteroides had habitat adaptability.(3)Using ATCC8293~Tas the reference genome,a total of 68,213 SNP sites were identified in 178 Leuconostoc mesenteroides strains.Among them,it was noted that the genes of 10 different dairy isolates were under positive selection pressure,and their main functions included folate metabolism,transcription regulation,and reduction characteristics.(4)The results of gene annotation showed that 178 strains of Leuconostoc mesenteroides were rich in carbohydrate hydrolase system.And different sources of dairy products are different;Yak milk has high iron content,and its AA1 family hydrolase is significantly higher than that of other isolated strains.Due to the different cheese texture,GT8 family hydrolase is significantly higher than other isolated sources.More than 85%of the strains involved in the study have bacteriocin genes,and the strains isolated from starter culture have lost their genomes due to their long-term existence in a nutrient-rich environment.In summary,the Leuconostoc mesenteroides population isolated from naturally fermented milk has high genetic diversity and strong habitat adaptability,and shows a significant segregation source aggregation trend,including abundant carbohydrate hydrolase system and strong bacteriocin-producing ability.This study will lay a solid genetic foundation for the further development and utilization of Leuconostoc mesenteroides. |
