Genetics and molecular biology of propionibacteria

Research in the genetics and molecular biology of propionibacteria is currently making much progress. In order to develop efficient DNA transfer systems for the genus Propionibacterium, dairy and environmental propionibacteria were screened for the presence of suitable plasmids as a first step. Following nucleotide sequence analysis, potential replication functions were identified on several Propionibacteriumplasmids such as pLME106/pRGO1, p545 and pLME108. Furthermore, ppnA, the gene encoding the propionicin SM1, was detected on pLME106. Three of these plasmids which had been fused with antibiotic resistance selection markers (ermE, cml, hygB) originating from bacteria with high G+C DNA content were recently successfully used as Escherichia coli - Propionibacterium shuttle vectors. DNA restriction/modification systems observed in propionibacteria have to be taken into account since successful DNA transformation at high rates (up to 10 8 Propionibacteriumtransformants/μg of DNA) succeeds only with plasmid DNA originating from propionibacteria with the same restriction/modification system(s) as the strain to be trans- formed, and not from E. coli hosts. The basis for an integrating vector has been set up after identifica- tion of a potential attP site and an adjacent integrase gene from a Propionibacteriumphage/prophage system. Finally, approximately 30 gene sequences with attributed coding functions from propionibacteria are available on databases. Propionibacterium / plasmid / bacteriophage / DNA transformation / genetics