Classification of propionic acid bacteria and approaches to applied genetics

Abstract

Strains of the genus Propionibacterium, which were recently c1assified within the new c1ass Aetinobaeteria, are grouped into cutaneous (medical) or dairy (c1assical) propionic acid bacteria.16S rDNA sequences of ail Propionibaeterium type strains and sorne new isolates were completed.A phylogenetic tree was constructed and current trees reexamined.The c1assical species P. thoenii, P. jensenii and P. acidipropionici were c1ustered in a group distinct from both the closely related elusters of P.freudenreiehii and P. eyclohexanieum.Within the cutaneous species, three groups were elustered: P. granulosum forms a distinct c1uster between the c1assical groups and a group containing P. avidum, P. aenes and P. propionicum, whereas P. lymphophilum is placed more distantly from any group in this tree.In order to differentiate Propionibaeterium isolates from other food-isolates a rapid multiplex-PCR (MPCR) method based on 16S rRNA-targeted oligonucleotides and particularly on a 16S rDNA-motif which tumed out to he specifie for the genus Propionibaeterium was developed.The MPCR-amplification could be performed within 1 d and reached detection limits of 10 3 colony forming units or 35 pg of DNA.The MPCR-method was used in various Propionibaeterium screening studies.In the course of screening antifungal and antibacterial activities of propionic acid bacteria, a Propionibaeterium jensenii strain containing a cryptic 7-kb plasmid was identified.This strain produced the bacteriocin Propionicin SM 1. Purification of Propionicin SM 1 and cloning of its genetic locus is currently under way.© Inra/Elsevier, Paris.propionibacteria / classification / PCR-identification /168 rDNA / genetic Résumé -Classification des bactéries propioniques et approches de génétique appliquée.Les souches du genre Propionibaeterium qui ont été récemment classées dans la nouvelle classe Actinobaeteria sont groupées, selon leur environnement, en bactéries propioniques cutanées (médicales) et laitières (classiques).Nous avons réalisé différentes séquences de l'ARNr 16S de toutes les souches du type Propionibacterium, dont certains nouvellement isolées.Nous avons construit un arbre phylogénétique et réexaminé les arbres existants.Les espèces classiques P. thoenii, P. jensenii et P. acidipropionici ont été réunis dans un cluster distinct des deux groupes P. freudenreiehii et Oral communication at the 2nd Symposium on Propionibacteria, Cork, Ireland, June 25-27, 1995.