Lactobacillus arizonensis is a later heterotypic synonym of Lactobacillus plantarum

This study examined the phylogenetic position of Lactobacillus arizonensis, a bacterium originally described in 2000, using multiple molecular techniques. Researchers compared the L. arizonensis type strain with L. plantarum and other related Lactobacillus species using 16S rRNA gene sequencing, ribotyping, rep-PCR fingerprinting, and DNA-DNA hybridization. The results consistently showed that L. arizonensis could not be distinguished from L. plantarum at the species level. The type strains exhibited identical 16S rRNA sequences (>99.4% similarity), identical ribotyping patterns, highly similar rep-PCR fingerprints, and DNA-DNA hybridization values of 73-100%, well above the 70% species threshold. The researchers propose that the original published 16S rRNA sequence for L. arizonensis may have contained sequencing errors or derived from contaminated cultures, as it showed anomalous divergence. Based on comprehensive molecular analysis, they conclude that L. arizonensis should be reclassified as a later heterotypic synonym of L. plantarum and formally renamed accordingly.

Key findings

• L. arizonensis type strain is indistinguishable from L. plantarum type strain using ribotyping, rep-PCR, 16S rRNA sequencing, and DNA-DNA hybridization analyses
• DNA-DNA hybridization values between L. arizonensis and L. plantarum strains ranged from 73-100%, exceeding the 70% species delineation threshold
• The original published L. arizonensis 16S rRNA sequence likely contained errors, as re-sequencing showed >99.4% identity to L. plantarum
• Multiple molecular techniques successfully differentiated L. arizonensis/L. plantarum from the related species L. pentosus and L. paraplantarum