Oxygen tolerance mechanism of Bifidobacterium animalis AR668-R1 based on genomic and phenotypic analyses

Bifidobacterium animalis plays a crucial role as a probiotic in maintaining human intestinal health. Oxygen tolerance characteristic of B. animalis AR668-R1 was investigated by using genomic and phenotypic analyses. Under aerobic condition, AR668-R1 exhibited higher specific growth rate (0.3463 h −1 ), which increased by 55.29% compared with AR668. The hydrogen peroxide accumulation of AR668-R1 was only 7.92 μmol/L, which was significantly lower than AR668 (104.69 μmol/L) with a 12.22-fold reduction. AR668-R1 exhibited the activities of NADH peroxidase (20.84 U) and NADH oxidase (12.73 U), respectively, with the increase of 0.60-fold and 1.05-fold higher than AR668. Comparative genomic analysis showed mutations across the entire genome of AR668-R1 including 73 amino acid mutations. The RT-qPCR and venn diagram analyses revealed that the key genes specific to aerobic condition were gene0321 , gene0478 and gene0759 responsible for cell membrane and ABC transporter. Single overexpression of three genes significantly increased the optical density by 109.87%, 81.97% and 142.06%, respectively, which viable counts were at least 3 orders of magnitude higher than the control strain (4.09 × 10CFU/mL). It is the first report that membrane proteins and ABC transporter are involved in regulating oxygen tolerance of B. animalis . • Oxygen tolerance mechanism of Bifidobacterium animalis AR668-R1 was elucidated. • AR668-R1 showed high antioxidant activity of NADH peroxidase and NADH oxidase. • Comparative genomics revealed 62 SNPs and 72 amino acid mutations in AR668-R1. • Gene0321 , gene0478 and gene0759 were associated with oxygen tolerance in AR668-R1.