Biomedical subjects

Pornpimon Kiatpapan

Publications and source records attributed to Pornpimon Kiatpapan.

4 recordsLinked to original sources

PubMed2005

The Burkholderia pseudomallei RpoE (AlgU) operon is involved in environmental stress tolerance and biofilm formation.

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.

Adaptation, Physiological↗

PubMed2004

Molecular analysis of promoter elements from Propionibacterium freudenreichii.

Propionibacterium freudenreichii is a commercially important microorganism that is used in the production of cheeses, cobalamin (vitamin B(12)), and propionic acid. Although a host-vector system in propionibacteria has been developed, there is little information available on the genetic background of the bacteria. To obtain genetic information to facilitate genetic engineering in propionibacteria, we cloned promoter regions from P. freudenreichii using Escherichia coli as a host at the first screening and a promoter-probe vector, pCVE1, which consists of the cholesterol oxidase (choA) gene from Streptomyces sp. as a reporter gene. Finally, nine clones with strong promoter activities in P. freudenreichii were screened by monitoring the choA gene expression and determining if the nucleotide sequences of the cloned DNA fragment were aligned. The initiation sites of these transcripts were determined by primer extension analysis. The putative consensus sequences corresponding to a -35 and -10 hexamer were found to be specific for P. freudenreichii, but not E. coli or other bacteria. Moreover, a new consensus heptamerous sequence between the -35 and -10 regions, termed the -16 region, was also found. It is possible that the putative consensus heptamer is functional and essential to promoter activity in P. freudenreichii. These results should provide new opportunities for controlled gene expression in P. freudenreichii.

Journal Article↗

PubMed2004

Effects of expression of hemA and hemB genes on production of porphyrin in Propionibacterium freudenreichii.

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 delta-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.

5-Aminolevulinate Synthetase↗

PubMed2002

Genetic manipulation system in propionibacteria.

Members of the genus Propionibacterium are widely used in the production of vitamin B12, tetrapyrrole compounds, and propionic acid as well as in probiotic and cheese industries. Shuttle vectors were developed in propionibacteria using replicons from endogenous plasmids in Propionibacterium and Escherichia coli and an appropriate selection marker. The efficient transformation was achieved using the shuttle vector prepared from Propionibacterium freudenreichii to overcome the high restriction modification system in propionibacteria. Expression vectors with native promoters for use in propionibacteria were also developed. Using this system, cholesterol oxidase, which is used as a diagnostic enzyme, was produced in P. freudenreichii. Genes involved in 5-aminolevulinic acid (ALA) and vitamin B12 biosynthesis in propionibacteria were isolated. ALA in propionibacteria could be synthesized via both the C4 pathway (condensation of glycine and succinyl CoA) and the C5 pathway (from glutamate). The hemA gene encoding ALA synthase from Rhodobacter spheroides, was overexpressed and ALA accumulated in P. freudenreichii. Thus, the genetic manipulation systems in propionibacteria will facilitate genetic studies of probiotics and the vitamin B12 biosynthetic pathway.

Journal Article↗