Identification of Bifidobacterium animalis subsp. lactis BL-99 isolated from infant intestine
YU Xuejian1, LIU Jinfeng2,3, ZHAO Ting1, MA Xia2,3, LIU Yiru1, LIU Weixian2,3, CHENG Kun1, ZHANG Xin1, CAO Yanhua1, XIN Di1, FENG Huijun1, LIU Fudong2,3, ZHAO Wen2,3, HONG Weilian2,3, YAO Su1*
1(China National Research Institute of Food and Fermentation Industries Co. Ltd., China Center of Industrial Culture Collection, Beijing 100015, China) 2(Inner Mongolia Dairy Technology Research Institute Co. Ltd., Hohhot 010110, China) 3(Inner Mongolia Yili Industrial Group Co. Ltd., Hohhot 010110, China)
Abstract: Strain BL-99 isolated from the infant intestine was systematically identified using nine strains of Bifidobacterium animalis including B. animalis subsp. lactis and B. animalis subsp. animalis from different sources as reference.Microbial identification technologies including morphology, physiological and biochemical analysis, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and whole genome sequencing were applied to establish the strain-level identification method suitable for the identification of strain BL-99. The MALDI-TOF MS identification score of strain BL-99 was 2.38, and the average nucleotide identity value of the strain BL-99 was 99.97% comparing with the type strain, which means the strain BL-99 was identified as Bifidobacterium animalis subsp. lactis based on colony morphology, physiological and biochemical properties, MALDI-TOF MS and whole genome sequencing using nine strains of B. animalis were the reference. Whole genome multilocus sequence typing analysis was carried out based on the 1 562 core genes of B. animalis subsp. lactis BL-99 and other 9 reference strains, and the whole-genome multilocus sequence typing (wgMLST) results showed that strain BL-99 could be effectively distinguished from reference strains. Single nucleotide polymorphism (SNP) analysis showed that the difference in SNP between different generations of B. animalis subsp. lactis BL-99 was 0, and the reference strain was higher than 32. Phylogenetic analysis further demonstrated that the SNP analysis can effectively distinguish B. animalis subsp. lactis BL-99 from reference strains. The method that combined phenotype and genotype established could provide a technical basis for the establishment of strain identification relative standards and promote the safer and wider application of probiotics in the food industry.
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