Lactobacillus sobrius Konstantinov et al. 2006 is a later synonym of Lactobacillus amylovorus Nakamura 1981

Abstract

While studying the taxonomy of six lactic acid bacterium isolates from Finnish porcine intestine and faeces, the taxonomic positions of Lactobacillus sobrius type strain DSM 16698T and strain AD5 based on comparative 16S rRNA sequence analysis were found to be controversial, as they showed high similarity to Lactobacillus amylovorus strains. Therefore, the taxonomy of these species was addressed in a polyphasic taxonomy study that included, in addition to re-evaluating the 16S rRNA gene sequence and DNA-DNA reassociation results, multilocus sequence analysis (MLSA) of the housekeeping genes encoding the phenylalanyl-tRNA synthase alpha subunit (pheS) and RNA polymerase alpha subunit (rpoA) as well as numerical analysis of HindIII and EcoRI ribotypes. 16S rRNA gene sequence analysis demonstrated a very high similarity between the L. sobrius and L. amylovorus type and reference strains and representative Finnish porcine isolates (99.6-99.9 %). The MLSA data showed the close phylogenetic relationship of these strains; pheS and rpoA gene sequence similarities were 98.5-100 % and 99.6-99.8 %, respectively. Numerical analyses of HindIII/EcoRI ribotypes placed these strains in a single cluster by both enzymes. Finally, the DNA-DNA reassociation experiments revealed high reassociation levels (higher than 79 %) between the strains. These results indicate that DSM 16698T, AD5 and the related porcine lactobacilli strains from Finland constitute a single species, Lactobacillus amylovorus, and that the name Lactobacillus sobrius should be considered as a later synonym of Lactobacillus amylovorus.