|
|
|
|
|
|
Spike Structure at the Interface between Gliding Mycoplasma mobile Cells and Glass Surfaces Visualized by Rapid-Freeze-and-Fracture Electron Microscopy. Makoto Miyata, 2004.Mycoplasma mobile is a flask-shaped bacteria that binds to a substrate and glides towards its tapered end, the so-called "head-like protrusion," by an unknown mechanism . To search for cellular structures underlying this motility, the cell-substrate interface of actively gliding cells was visualized by rapid-freeze-and-freeze-fracture rotary-shadow electron microscopy . Novel structures, called "spikes," were observed to protrude from the cell membrane and attach to the glass surface at their distal end . The spikes were on average 50 nm in length and 4 nm in diameter, most abundant around the head, and not observed in a nonbinding mutant . The spikes may be involved in the mechanism of binding, gliding, or both . Inhibition of Human Cytomegalovirus Replication by Benzimidazole Nucleosides Involves Three Distinct Mechanisms. David L. Evers, 2004.The benzimidazole nucleosides 2-bromo-5,6-dichloro-1-(ß-D-ribofuranosyl)benzimidazole (BDCRB) and 2-isopropylamino-5,6-dichloro-1-(ß-L-ribofuranosyl)benzimidazole (1263W94, or maribavir) are potent and selective inhibitors of human cytomegalovirus (HCMV) replication . These inhibitors act by two different mechanisms: BDCRB blocks the processing and maturation of viral DNA, whereas maribavir prevents viral DNA synthesis and capsid nuclear egress . In order to determine by which of these two mechanisms other benzimidazole nucleosides acted, we performed time-of-addition studies and other experiments with selected new analogs . We found that the erythrofuranosyl analog and the  -lyxofuranosyl analog acted late in the viral replication cycle, similar to BDCRB . In marked contrast, the
-5'-deoxylyxofuranosyl analog of 2,5,6-trichloro-1-(ß-D-ribofuranosyl)benzimidazole (compound UMJD1311) acted early in the replication cycle, too early to be consistent with either mechanism . Similar to other reports on early acting inhibitors of herpesviruses, compound 1311 was multiplicity of infection dependent, an observation that could not be reproduced with UV-inactivated virus . HCMV isolates resistant to BDCRB and maribavir were sensitive to compound 1311, as were viruses resistant to ganciclovir, cidofovir, and foscarnet . The preincubation of host cells with compound 1311 and removal prior to the addition of HCMV did not produce an antiviral cellular response . We conclude that this newly discovered early mode of action occurs at a stage of viral replication after entry to cells but prior to viral DNA synthesis, thereby strongly suggesting that the trisubstituted benzimidazole nucleoside series possesses three distinct biochemical modes of action for inhibition of HCMV replication .
The Enigmatic Escherichia coli fadE Gene Is yafH. John W. Campbell, 2002.The identity of the gene encoding acyl coenzyme A dehydrogenase is a major remaining mystery of the Escherichia coli fatty acid degradation (fad) regulon . Our prior genome array analyses showed that transcription of the yafH gene is controlled by the FadR regulatory protein . We now report direct experimental proof that yafH and fadE are the same gene . Functional Analysis of the Heat Shock Regulator HrcA of Chlamydia trachomatis. Adam C. Wilson, 2002.HrcA is a regulator of bacterial heat shock gene expression that binds to a cis-acting DNA element called CIRCE . It has been proposed that HrcA and CIRCE function as a repressor-operator pair . We have purified recombinant HrcA from the pathogenic bacterium Chlamydia trachomatis and have shown that it is a DNA-binding protein that functions as a negative regulator of transcription . HrcA bound specifically to the CIRCE element in a concentration-dependent manner . HrcA repressed the in vitro transcription of a chlamydial heat shock promoter, and this repression was promoter specific . HrcA-mediated repression appears to be dependent on the topological state of the promoter, as repression on a supercoiled promoter template was greater than that on a linearized template . These results provide direct support for the role of HrcA as a transcriptional repressor in bacteria . This is the first report of the in vitro reconstitution of transcriptional regulation in Chlamydia . It Is All about Metabolic Fluxes. Jens Nielsen, 2003. Culture-Independent Analysis of Probiotic Products by Denaturing Gradient Gel Electrophoresis. R. Temmerman, 2003.In order to obtain functional and safe probiotic products for human consumption, fast and reliable quality control of these products is crucial . Currently, analysis of most probiotics is still based on culture-dependent methods involving the use of specific isolation media and identification of a limited number of isolates, which makes this approach relatively insensitive, laborious, and time-consuming . In this study, a collection of 10 probiotic products, including four dairy products, one fruit drink, and five freeze-dried products, were subjected to microbial analysis by using a culture-independent approach, and the results were compared with the results of a conventional culture-dependent analysis . The culture-independent approach involved extraction of total bacterial DNA directly from the product, PCR amplification of the V3 region of the 16S ribosomal DNA, and separation of the amplicons on a denaturing gradient gel . Digital capturing and processing of denaturing gradient gel electrophoresis (DGGE) band patterns allowed direct identification of the amplicons at the species level . This whole culture-independent approach can be performed in less than 30 h . Compared with culture-dependent analysis, the DGGE approach was found to have a much higher sensitivity for detection of microbial strains in probiotic products in a fast, reliable, and reproducible manner . Unfortunately, as reported in previous studies in which the culture-dependent approach was used, a rather high percentage of probiotic products suffered from incorrect labeling and yielded low bacterial counts, which may decrease their probiotic potential . Reductive Dehalogenation of Chlorobenzene Congeners in Cell Extracts of Dehalococcoides sp . Strain CBDB1. Tina Hölscher, 2003.Enzymatic reductive dehalogenation of tri-, tetra-, penta-, and hexachlorobenzenes was demonstrated in cell extracts with low protein concentration (0.5 to 1 µg of protein/ml) derived from the chlorobenzene-respiring anaerobe Dehalococcoides sp . strain CBDB1 . 1,2,3-trichlorobenzene dehalogenase activity was associated with the membrane fraction . Light-reversible inhibition by alkyl iodides indicated the presence of a corrinoid cofactor .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
