The complete genome sequence of Bifidobacterium animalis subsp. lactis 01 and its integral components of antioxidant defense system

Abstract

The strain Bifidobacterium animalis 01, isolated from centenarians, showed promising antioxidant potential in our previous studies. In this study, the genome information on strain 01 and the important antioxidant components are presented. The complete genome comprises a single circular chromosome (1,931,632 bp; 60.49% G + C content) with 1569 coding DNA sequences, 52 tRNA, and 9 rRNA operons. Based on phylogenomic analyses, strain 01 was designated as B. animalis subsp. lactis 01. The genomic analysis reveals that at least eight protein-coding genes are antioxidant-related genes. The conditions for simulating the oxidative stress have been determined. The results of quantitative reverse transcription PCR further demonstrated that the genes encoding the thioredoxin system (ahpC, ahpF, bcp, trxB, trxA, nrdH, and msrAB) and non-enzyme factors of the divalent cation transporter gene (mntH) were upregulated under the H₂O₂ challenge, indicating that the eight genes were effective components of the antioxidant system. The results of this study could benefit for understanding the antioxidant mechanism of B. animalis 01 and future utilization of it as a potential antioxidant agent.

Keywords: Antioxidant activity; Bifidobacterium animalis subsp. lactis 01; Complete genome sequence; H2O2 challenge.

Fig. 1

Circular genome map of Bifidobacterium animalis subsp. lactis 01. Circles are shown from the outside to inner. Ring 1, Genome sequences. Ring 2 and 3, COG annotated coding sequences. Ring 4, KEGG enzymes. Ring 5, RNA genes. Ring 6, GC content. Ring 7, GC skew. Very short features were enlarged to enhance visibility. Clustered genes, such as several rRNA genes, may appear as one line due to space limitations. The image was created by software Circos

Fig. 2

Effect of H₂O₂ on survival and production of ROS in B. animalis subsp. lactis 01. a Survival of early exponential phase B. animalis subsp. lactis 01 over 30 min and 60 min in MRS broth medium with H₂O₂ concentration of 0, 0.5, 1.0, 1.5, 2.0, and 2.5 mM. b Representative histograms of DCFH-DA fluorescence. Black line represented control B. animalis subsp. lactis 01 cells without H₂O₂ treatment (0 min). Green line represented B. animalis subsp. lactis 01 cells treated with 1.5 mM H₂O₂ (30 min), while red line represented cells treated with 1.5 mM H₂O₂ (60 min). c The percentage of mean fluorescence intensity relative to control cells. Data presented are the mean ± SD (n = 3). Error bars represent standard deviations. Statistical significance was calculated using Holm–Sidak Student’s t test (*p < 0.05, **p < 0.01, and ***p < 0.001)

Fig. 3

Effects of hydrogen peroxide on expressions of antioxidant-related genes in B. animalis subsp. lactis 01. The bar chart showed the relative mRNA levels of eight tested genes of cells in the presence of 1.5 mM H₂O₂ at the early exponential phase. Data presented are the mean ± SD (n = 3). Error bars represent standard deviations. Statistical significance was calculated using Holm–Sidak Student’s t test (*p < 0.05 and **p < 0.01)