Summary auto-generated
This paper addresses a 25-year taxonomic problem regarding Lactobacillus casei classification. The authors present evidence that the current type strain ATCC 393 does not accurately represent L. casei. Extensive DNA-DNA hybridization, PCR fingerprinting, 16S rRNA sequencing, and recA gene analysis consistently show that ATCC 393 is genetically distinct from the majority of strains labeled L. casei and instead closely resembles L. zeae. In contrast, ATCC 334 and L. paracasei strains share identical 16S rRNA sequences and high genetic relatedness (61-100% DNA homology), indicating they belong to the same taxon. The authors petition the Judicial Commission to: (1) reclassify ATCC 393 as L. zeae since it is unsuitable as the L. casei type strain, (2) unite L. casei and L. paracasei under the older name L. casei, and (3) designate ATCC 334 as the neotype strain for L. casei. This proposal resolves ongoing confusion in bacterial nomenclature, particularly important for industrial applications using these commonly isolated food bacteria.
Key findings
- ATCC 393, the current type strain of L. casei, is genetically unsuitable and closely related to L. zeae rather than true L. casei strains
- ATCC 334 and L. paracasei strains are genetically identical and belong to the same taxon based on DNA homology and 16S rRNA sequences
- Multiple molecular techniques (DNA-DNA hybridization, PCR, 16S rRNA, 23S-5S rRNA, and recA gene analysis) consistently support reclassification over 25 years of research
- ATCC 393 should be reclassified as L. zeae, while ATCC 334 should become the neotype for L. casei
- L. paracasei should be rejected as a species name since it represents the same taxon as L. casei
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Abstract
F. Dellaglio, G. E. Felis and S. Torriani
Dipartimento Scientifico e Tecnologico, Facolta di Scienze MM. FF. NN., Universita degli Studi di Verona, Strada le Grazie 15, 3714 Verona, Italy
On the basis of considerable published evidence, it is concluded that the species Lactobacillus casei is not correctly represented by the strain actually designated as the type strain ATCC 393. It is proposed that the Judicial Commission consider: (1) that ATCC 393(T) is scientifically unsuitable as the type strain of Lactobacillus casei and should be reclassified as Lactobacillus zeae; (2) that Lactobacillus casei ATCC 334 and Lactobacillus paracasei strains are members of the same taxon and therefore can be united within the name Lactobacillus casei (Rules 42 and 23a), the name Lactobacillus paracasei being rejected; and (3) designating ATCC 334 as the neotype strain for the species Lactobacillus casei.