Effects of Global and Specific DNA-Binding Proteins on Transcriptional Regulation of the E. coli bgl Operon.

Using reporter gene (lacZ) transcriptional fusions, we examined the transcriptional dependencies of the bgl promoter (Pbgl) and the entire operon regulatory region (Pbgl-bglG) on eight transcription factors as well as the inducer, salicin, and an IS5 insertion upstream of Pbgl. Crp-cAMP is the primary activator of both Pbgl and the bgl operon, while H-NS is a strong dominant operon repressor but only a weak repressor of Pbgl. H-NS may exert its repressive effect by looping the DNA at two binding sites. StpA is a relatively weak repressor in the absence of H-NS, while Fis also has a weak repressive effect. Salicin has no effect on Pbgl activity but causes a 30-fold induction of bgl operon expression. Induction depends on the activity of the BglF transporter/kinase. IS5 insertion has only a moderate effect on Pbgl but causes a much greater activation of the bgl operon expression by preventing the full repressive effects of H-NS and StpA. While several other transcription factors (BglJ, RcsB, and LeuO) have been reported to influence bgl operon transcription when overexpressed, they had little or no effect when present at wild type levels. These results indicate the important transcriptional regulatory mechanisms operative on the bgl operon in E. coli.

Comment on "the IS6 family, a clinically important group of insertion sequences including IS26" by Varani and co-authors.

The insertion sequence IS26 has long been known to play a major role in the recruitment of antibiotic resistance genes into the mobile resistance gene pool of Gram-negative bacteria and IS26 also plays a major role in their subsequent broad dissemination. Related IS, IS431/257 and IS1216 are important in the same roles in Gram positive bacteria. However, until recently the properties of IS26 movement that could potentially explain this ability had not been explored. A much needed insight has come from our recent demonstration that IS26 uses a novel targeted mechanism that is conservative. The targeted conservative mechanism is much more efficient than the known replicative mechanism, which is now more accurately called copy-in. A recent review "The IS6 family, a clinically important group of insertion sequences including IS26" by Varani, He, Siguier, Ross and Chandler published in Mobile DNA has substantially misrepresented the recent studies on the targeted conservative mechanism and at the same time incorrectly implied that any mechanism established for IS26 can be assumed to apply to a range of IS that are at best very distantly related. A few of the most important issues are examined in this comment. Readers are advised to consult the original literature to check facts before drawing firm conclusions.

Strain differentiation of 13 indigenous Mycobacterium bovis isolates from infected cattle by restriction fragment length polymorphism analysis.

Mycobacterium bovis is mainly detected in cattle throughout the world. This bacterium is considered the main causative agent of tuberculosis in man and animals. M. bovis is also reported to be endemic in badgers and in farmed and feral deer. The disease caused by M. bovis is a slow progressive disease with clinical signs not apparent until late in the disease process. key factors for effective control of tuberculosis includes rapid detection, adequate therapy, and contact tracing to halt further transmission. However, in order to locate the source and route of transmission of M. bovis infection, a thorough epidemiological analysis is routinely carried out, that could lead to the control of disease in the herds and avoid economic losses. Recent developments in DNA technology and molecular biology have led to methods for the rapid detection of mycobacterium DNA. Among a number of described molecular methods, IS6110 fingerprinting is the recommended standard primary genotyping method and the most widely used worldwide. In this study, we used restriction fragment length polymorphism analysis with probes derived from the insertion element IS6110, the polymorphic GC-rich sequence (PGRS), and the direct repeat (DR) sequence which proved to be a useful method for differentiating M. bovis strains. A total of 13M. bovis samples from infected cattle in the West Azerbaijan Province of Iran were included in the study. The samples were submitted to the Tuberculosis Reference Laboratory at the Razi Vaccine and Serum Research Institute, Karaj. All isolates were cultivated on Lowenstein Jensen media with pyruvate (pyruvic acid), and then identified according to The World Organization for Animal Health (OIE) recommendations. The extracted genomic DNA samples of the isolates in the study were subjected to IS6110 primers, digested with restriction enzyme PvuII, and hybridized by oligonucleotide probes PGRS and DR. Polymorphic banding patterns obtained after hybridization discriminated the M. bovis strains and a database of strain types was established. Based on our results, the 13 isolates showed five different DNA patterns with a PGRS probe and similarly five patterns were obtained with the DR probe. PP-1 pattern was found almost among all the isolates while a distinct DNA pattern PP-3 was seen specifically from the West Azerbaijan Province.

Bordetella holmesii infection: current knowledge and a vision for future research.

Bordetella holmesii is a recently recognized Gram-negative bacterium causing both pertussis-like respiratory symptoms and invasive infections, such as bacteremia, pneumonia, meningitis, arthritis, pericarditis and endocarditis. Few data are available on its epidemiological characteristics, mostly related to respiratory infections. However, these are frequently misdiagnosed as a Bordetella pertussis infection as most diagnostic tests routinely used are not species-specific, thus biasing the epidemiological studies of both strains, as well as the efficacy studies on pertussis vaccination. There is no accepted agreement on treatment and it remains unknown if antimicrobial prophylaxis is indicated in certain clinical settings. We review here the current knowledge on B. holmesii and the need for further research.