Bifidobacterium lactis sp. nov., a moderately oxygen tolerant species isolated from fermented milk
1997
Meile, L. | Ludwig, W. | Rueger, U. | Gut, C. | Kaufmann, P. | Dasen, G. | Wenger, S. | Teuber, M.
A selection procedure was developed to isolate Bifidobacterium strains from food and faeces which are able to grow under oxidative stress conditions. Strain UR1, an isolate from a French yoghurt, was able to grow at elevated oxygen concentrations above 5% oxygen in liquid media containing 0.3 mM paraquat (methylviologen). In fermenter cultures, strain UR1 produced considerable amounts of formate (up to 23 mM) depending on the oxygen-stress conditions. We sequenced the 16S rRNA gene cloned from UR1 genomic DNA, compared it with that from 21 Bifidobacterium species and constructed a phylogenetic tree by alignment analysis. The most related species of strain UR1 was calculated to be Bifidobacterium animalis DSM 20104. DNA-DNA hybridizations between the genomes of strain UR1, B. animalis DSM 20104 and B. longum DSM 20219 showed only weak homology (27% and <10%, respectively). Both findings strongly supported a distinct species-status for strain UR1. In addition, properties like enzyme profiles (API ZYM), utilization of carbohydrates (API CH 50), the G+C content of 61.9 mol% and the high tolerance towards oxygen stress differ from those of B. animalis. Therefore, we concluded that strain UR1 has to be regarded as a new species which we named Bifidobacterium lactis. This name honours the fact that the species has been isolated on several occasions from fermented milk.
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