T. S. Oberg

Comparison of the Complete Genome Sequences of Bifidobacterium animalis subsp. lactis DSM 10140 and Bl-04

Bifidobacteria are important members of the human gut flora, especially in infants. Comparative genomic analysis of two Bifidobacterium animalis subsp. lactis strains revealed evolution by internal deletion of consecutive spacer-repeat units within a novel clustered regularly interspaced short palindromic repeat locus, which represented the largest differential content between the two genomes. Additionally, 47 single nucleotide polymorphisms were identified, consisting primarily of nonsynonymous mutations, indicating positive selection and/or recent divergence. A particular nonsynonymous mutation in a putative glucose transporter was linked to a negative phenotypic effect on the ability of the variant to catabolize glucose, consistent with a modification in the predicted protein transmembrane topology. Comparative genome sequence analysis of three Bifidobacterium species provided a core genome set of 1,117 orthologs complemented by a pan-genome of 2,445 genes. The genome sequences of the intestinal bacterium B. animalis subsp. lactis provide insights into rapid genome evolution and the genetic basis for adaptation to the human gut environment, notably with regard to catabolism of dietary carbohydrates, resistance to bile and acid, and interaction with the intestinal epithelium. The high degree of genome conservation observed between the two strains in terms of size, organization, and sequence is indicative of a genomically monomorphic subspecies and explains the inability to differentiate the strains by standard techniques such as pulsed-field gel electrophoresis.

Identification of plasmalogens in the cytoplasmic membrane of Bifidobacterium animalis subsp. lactis

ABSTRACT Plasmalogens are ether-linked lipids that may influence oxidative stress resistance of eukaryotic cell membranes. Since bacterial membrane composition can influence environmental stress resistance, we explored the prevalence of plasmalogens in the cytoplasmic membrane of Bifidobacterium animalis subsp. lactis. Results showed plasmalogens are a major component of the B. animalis subsp. lactis membrane.

Transcriptome analysis of Bifidobacterium longum strains that show a differential response to hydrogen peroxide stress

Consumer and commercial interest in foods containing probiotic bifidobacteria is increasing. However, because bifidobacteria are anaerobic, oxidative stress can diminish cell viability during production and storage of bioactive foods. We previously found Bifidobacterium longum strain NCC2705 had significantly greater intrinsic and inducible resistance to hydrogen peroxide (H2O2) than strain D2957. Here, we explored the basis for these differences by examining the transcriptional responses of both strains to sub-lethal H2O2 exposure for 5- or 60-min. Strain NCC2705 had 288 genes that were differentially expressed after the 5-min treatment and 114 differentially expressed genes after the 60-min treatment. In contrast, strain D2957 had only 21 and 90 differentially expressed genes after the 5- and 60-min treatments, respectively. Both strains showed up-regulation of genes coding enzymes implicated in oxidative stress resistance, such as thioredoxin, thioredoxin reductase, peroxiredoxin, ferredoxin, glutaredoxin, and anaerobic ribonucleotide reductase, but induction levels were typically highest in NCC2705. Compared to D2957, NCC2705 also had more up-regulated genes involved in transcriptional regulation and more down-regulated genes involved in sugar transport and metabolism. These results provide a greater understanding of the molecular basis for oxidative stress resistance in B. longum and the factors that contribute to strain-to-strain variability in survival in bioactive food products.

Correction to: Intrinsic and inducible resistance to hydrogen peroxide in Bifidobacterium species

In the published article, the co-author Abdelmoneim Abdalla’s affiliation has been published incompletely. The additional affiliation is given below: