The complete nucleotide sequence of pRGO1, a cryptic plasmid from Propionibacterium acidipropionici E214, was determined. pRGO1 is 6,868 bp long, and its G؉C content is 65.0%. Frame analysis of the sequence revealed six open reading frames, which were designated Orf1 to Orf6. The deduced amino acid sequences of Orf1 and Orf2 showed extensive similarities to an initiator of plasmid replication, the Rep protein, of various plasmids of gram-positive bacteria. The amino acid sequence of the putative translation product of orf3 exhibited a high degree of similarity to the amino acid sequences of DNA invertase in several bacteria. For the putative translation products of orf4, orf5, and orf6, on the other hand, no homologous sequences were found. The function of these open reading frames was studied by deletion analysis. A shuttle vector, pPK705, was constructed for shuttling between Escherichia coli and a Propionibacterium strain containing orf1 (repA), orf2 (repB), orf5, and orf6 from pRGO1, pUC18, and the hygromycin B-resistant gene as a drug marker. Shuttle vector pPK705 successfully transformed Propionibacterium freudenreichii subsp. shermanii IFO12426 by electroporation at an efficiency of 8 ؋ 10 6 CFU/g of DNA under optimized conditions. Transformation of various species of propionibacteria with pPK705 was also performed at efficiencies of about 10 4 to 10 7 CFU/g of DNA. The vector was stably maintained in strains of P. freudenreichii subsp. shermanii, P. freudenreichii, P. pentosaceum, and P. freudenreichii subsp. freudenreichii grown under nonselective conditions. Successful manipulation of a host-vector system in propionibacteria should facilitate genetic studies and lead to creation of genes that are useful industrially.Propionibacteria, which have a wide range of probiotic activity, are used in making dairy foods, such as cheese, for the production of vitamin B 12 , tetrapyrrole compounds, and propionic acid (8,15,21), in bread baking, as starters for ensilage, and in some pharmaceutical preparations (35). To elucidate the biosynthetic pathways of vitamin B 12 and siroheme in Propionibacterium, we previously identified several genes coding for the enzymes involved in production of tetrapyrrole derivatives (hemYHBXRL) (11,12) and vitamin B 12 (cobA, cbiO) (30).Development of genetic manipulation in propionibacteria has progressed slowly due to a lack of detailed information on the genetics of the bacteria and a lack of an appropriate plasmid that can serve as a possible transformation vector. A number of plasmids from Propionibacterium acidipropionici, P. freudenreichii, and P. jensenii, ranging in size from 4.4 to more than 119 MDa, have been described (19,24). However, neither analysis of a plasmid DNA sequence nor construction of a vector for propionibacteria has been reported. To establish a versatile vector system to facilitate genetic analysis and to allow the transfer of a gene of interest, we investigated the development of a host-vector system in propionibacteria.We succeeded in determining the co...

Burkholderia pseudomallei, the causative agent of melioidosis, can be isolated from soil and water. To persist, adapt and survive within and outside their human host, bacteria rely on regulatory mechanisms that allow them to respond rapidly to stressful situations. We have examined the possible role of B. pseudomallei alternative sigma factor sigma(E) (RpoE) in the stress response and found that rpoE and its putative regulators (bprE-rseB-mucD) are transcribed in a single transcriptional unit. Inactivation of the rpoE operon changed the B. pseudomallei phenotype. Changes included increased susceptibility to killing by menadione and H(2)O(2), susceptibility to high osmolarity, reduced ability to form biofilms, and reduced survival in macrophage J774A.1. Therefore, we conclude that rpoE controls gene expression that contributes, at least in part, to B. pseudomallei adaptation to adverse environmental conditions.

Several promoters from Propionibacterium freudenreichii subsp. shermanii were isolated using a promoter probe vector, pCVE1, containing the Streptomyces cholesterol oxidase gene (choA) as a reporter gene. Three of four promoters isolated exhibiting a strong activity in Escherichia coli also expressed a strong activity in P. freudenreichii subsp. shermanii IFO12426. Using two promoters with a strong activity and a previously constructed shuttle vector, pPK705, shuttling between E. coli and Propionibacterium. we constructed expression vectors for propionibacteria. To overproduce 5-aminolevulinic acid (ALA), which is the first intermediate in the synthesis of porphyrins, the ALA synthase gene (hemA) from Rhodobacter sphaeroides was recombined with the expression vectors. The activity of ALA synthase in the recombinant P freudenreichii subsp. shermanii increased about 70-fold that in the strain without a vector. The recombinant Propionibacterium produced ALA at a maximum concentration of 8.6 mM in the absence of levulinic acid, an inhibitor of ALA dehydratase, with 1% glucose as a carbon source. The recombinant P. freudenreichii accumulated 18.8 mmol/g cells ALA in the presence of 1 mM levulinic acid and 30 mM glycine. The construction of an efficient expression vector will facilitate genetic studies of a vitamin B12 producer, Propionibacterium.

-Propionibacterium freudenreichii is a commercially important bacterium that is used in the production of cheeses, cobalamin (vitamin B 12 ) and propionic acid. Metabolic engineering using genetically improved strains will make the fermentation process more economical and also enhance the quality of the products. Host-vector systems and expression vectors using strong promoters from P. freudenreichii were developed in propionibacteria. By using these expression vectors and amplification of various genes, productions of 5-aminolevulinic acid, tetrapyrrole compounds and vitamin B 12 were reported. Here, we review the advancement of genetic engineering in P. freudenreichii in recent years, covering the molecular aspects of the formation of tetrapyrrole compounds and vitamin B12.

The genus Propionibacterium has a wide range of probiotic activities that are exploited in dairy and fermentation systems such as cheeses, propionic acid, and tetrapyrrole compounds. In order to improve production of tetrapyrrole compounds, we expressed the hemA gene, which encodes ␦-aminolevulinic acid (ALA) synthase from Rhodobacter sphaeroides, and the hemB gene, which encodes porphobilinogen (PBG) synthase from Propionibacterium freudenreichii subsp. shermanii IFO12424, either monocistronically or polycistronically in strain IFO12426. The recombinant strains accumulated larger amounts of ALA and PBG, with resultant 28-to 33-fold-higher production of porphyrinogens, such as uroporphyrinogen and coproporphyrinogen, than those observed in strain IFO12426, which harbored the shuttle vector pPK705.