|
|
|
|
|
|
Biofilms 2003: Emerging Themes and Challenges in Studies of Surface-Associated Microbial Life. Matthew R. Parsek, 2004. Rhodospirillum centenum Utilizes Separate Motor and Switch Components To Control Lateral and Polar Flagellum Rotation. Jonathan McClain, 2002.Rhodospirillum centenum is a purple photosynthetic bacterium that is capable of differentiating from vibrioid swimming cells that contain a single polar flagellum into rod-shaped swarming cells that have a polar flagellum plus numerous lateral flagella . Microscopic studies have demonstrated that the polar flagellum is constitutively present and that the lateral flagella are found only when the cells are grown on solidified or viscous medium . In this study, we demonstrated that R . centenum contains two sets of motor and switch genes, one set for the lateral flagella and the other for the polar flagellum . Electron microscopic analysis indicated that polar and lateral flagellum-specific FliG, FliM, and FliN switch proteins are necessary for assembly of the respective flagella . In contrast, separate polar and lateral MotA and MotB motor subunits are shown to be required for motility but are not needed for the synthesis of polar and lateral flagella . Phylogenetic analysis indicates that the polar and lateral FliG, FliM, and FliN switch proteins are closely related and most likely arose as a gene duplication event . However, phylogenetic analysis of the MotA and MotB motor subunits suggests that the polar flagellum may have obtained a set of motor genes through a lateral transfer event . Identification of the DNA Binding Sites of PerA, the Transcriptional Activator of the bfp and per Operons in Enteropathogenic Escherichia coli. J. Antonio Ibarra, 2003.The bundle-forming pilus (BFP) is an important virulence factor for enteropathogenic Escherichia coli (EPEC) . Genes involved in its biogenesis and regulation are tightly regulated by PerA (BfpT), a member of the AraC/XylS family of transcriptional regulators . The aim of this work was to purify PerA and determine its association with bfpA and perA (bfpT) regulatory regions by electrophoretic mobility shift and DNase I footprinting assays . PerA was purified as a maltose-binding protein (MBP) fusion, which was capable of complementing bfpA expression and which was able to restore the localized adherence phenotype of an EPEC perA mutant strain . Upstream of bfpA and perA, MBP-PerA recognized with similar affinity asymmetric nucleotide sequences in which a 29-bp-long AT-rich consensus motif was identified . These DNA motifs share 66% identity and were previously shown, by deletion analysis, to be involved in the PerA-dependent expression of both genes . Interestingly, in perA, this motif spans the sequence between positions -75 and -47, approximately one helix turn upstream of the -35 promoter sequence, while in bfpA, it spans the sequence between positions -83 and -55, approximately two helix turns upstream from the promoter . An additional PerA binding site was identified at the 5' end of the bfpA structural gene, which was not required for its activation . Experiments with LexA-PerA fusions suggested that PerA acts as a monomer to activate the transcription of both perA and bfpA, in contrast to what has been documented for other members of this family of transcriptional regulators . Biotransformation of Natural and Synthetic Isoflavonoids by Two Recombinant Microbial Enzymes. Michael Seeger, 2003.Isolation and synthesis of isoflavonoids has become a frequent endeavor, due to their interesting biological activities . The introduction of hydroxyl groups into isoflavonoids by the use of enzymes represents an attractive alternative to conventional chemical synthesis . In this study, the capabilities of biphenyl-2,3-dioxygenase (BphA) and biphenyl-2,3-dihydrodiol 2,3-dehydrogenase (BphB) of Burkholderia sp . strain LB400 to biotransform 14 isoflavonoids synthesized in the laboratory were investigated by using recombinant Escherichia coli strains containing plasmid vectors expressing the bphA1A2A3A4 or bphA1A2A3A4B genes of strain LB400 . The use of BphA and BphB allowed us to biotransform 7-hydroxy-8-methylisoflavone and 7-hydroxyisoflavone into 7,2',3'-trihydroxy-8-methylisoflavone and 7,3',4'-trihydroxyisoflavone, respectively . The compound 2'-fluoro-7-hydroxy-8-methylisoflavone was dihydroxylated by BphA at ortho-fluorinated and meta positions of ring B, with concomitant dehalogenation leading to 7,2',3',-trihydroxy-8-methylisoflavone . Daidzein (7,4'-dihydroxyisoflavone) was biotransformed by BphA, generating 7,2',4'-trihydroxyisoflavone after dehydration . Biotransformation products were analyzed by gas chromatography-mass spectrometry and nuclear magnetic resonance techniques .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
