Intragenic tandem repeat variation between Legionella pneumophila strains

<p>Abstract</p> <p>Background</p> <p>Bacterial genomes harbour a large number of tandem repeats, yet the possible phenotypic effects of those found within the coding region of genes are only beginning to be examined. Evidence exists from other organisms that these repeats can be involved in the evolution of new genes, gene regulation, adaptation, resistance to environmental stresses, and avoidance of the immune system.</p> <p>Results</p> <p>In this study, we have investigated the presence and variability in copy number of intragenic tandemly repeated sequences in the genome of <it>Legionella pneumophila</it>, the etiological agent of a severe pneumonia known as Legionnaires' disease. Within the genome of the Philadelphia strain, we have identified 26 intragenic tandem repeat sequences using conservative selection criteria. Of these, seven were "polymorphic" in terms of repeat copy number between a large number of <it>L. pneumophila </it>serogroup 1 strains. These strains were collected from a wide variety of environments and patients in several geographical regions. Within this panel of strains, all but one of these seven genes exhibited statistically different patterns in repeat copy number between samples from different origins (environmental, clinical, and hot springs).</p> <p>Conclusion</p> <p>These results support the hypothesis that intragenic tandem repeats could play a role in virulence and adaptation to different environments. While tandem repeats are an increasingly popular focus of molecular typing studies in prokaryotes, including in <it>L. pneumophila</it>, this study is the first examining the difference in tandem repeat distribution as a function of clinical or environmental origin.</p

Effect of iron on the expression of sirR and sitABC in biofilm-associated Staphylococcus epidermidis

BACKGROUND: Different gene expression patterns correlate with the altered phenotype in biofilm-associated bacteria. Iron and iron-linked genes are thought to play a key-role in biofilm formation. The expression of Fe-linked genes (sirR, sitABC operon) in Staphylococcus epidermidis, was compared in planktonic versus sessile bacteria in vitro and in vivo in a subcutaneous foreign body rat model. RESULTS: In vitro in a Fe-limited environment, the planktonic form of S. epidermidis produces siderophores and grows slower than in Fe-rich environment. The expression of sirR in planktonic bacteria, in vitro, was not different in medium without Fe or with 1 μM FeCl(3). High Fe concentrations (25 μM FeCl(3)) increased expression of sirR transiently during the early phase of incubation. Expression of sitC in vitro, in planktonic bacteria, was inversely correlated with sirR expression in medium with 25 μM FeCl(3): sitC expression decreased for the first 3 hours followed by an up regulation. In sessile bacteria in vitro, sirR expression was high and independent of the Fe concentration. The expression of sitC was not inversely correlated to sirR expression. In vivo, expression levels of sirR and of sitABC were high during the initial phase after implantation and, after a transient decrease, remained stable over a period of two weeks. CONCLUSION: Our data suggest that the expression of sirR and the regulatory effect of sirR on the sitABC operon are different in planktonic and sessile bacteria

Sociale activering in Vlaamse OCMW's: een empirische toetsing

status: publishe

Selection and Characterization of DNA Aptamers for Egg White Lysozyme

We have selected aptamers binding to lysozyme from a DNA library using capillary electrophoresis-systematic evolution of ligands by exponential enrichment. During the selection process the dissociation constant of the ssDNA pool decreased from the micromolar to the low nanomolar range within five rounds of selection. The final aptamer had a dissociation constant of 2.8 ± 0.3 nM, 6.1 ± 0.5 nM, and 52.9 ± 9.1 nM as determined by fluorescence anisotropy, surface plasmon resonance and affinity capillary electrophoresis respectively. The aptamers were successfully challenged for specificity against other egg white proteins. The high affinity aptamers open up possibilities for the development of aptamer based food and medical diagnostics

Selection and Characterization of DNA Aptamers for Egg White

molecule

Secretory production of biologically active rat interleukin-2 by Clostridium acetobutylicum

The search for effective means of selectively delivering high therapeutic doses of anti-cancer agents to tumors has explored a variety of systems in the last decade. The ability of intravenously injected clostridial spores to infiltrate and thence selectively germinate in the hypoxic regions of solid tumors is exquisitely specific, making this system an interesting addition to the anti-cancer therapy arsenal. To increase the number of therapeutic proteins potentially useful for cancer treatment we have tested the possibility of Clostridium acetobutylicum to secrete rat interleukin-2 (rIL2). Therefore, rIL2 cDNA was placed under the control of the endo-beta-1,4-glucanase promoter and signal sequence of C saccharobutylicum. Recombinant C acetobutylicum containing the relevant construct secreted up to 800 mu g l(-1) biologically active rIL2. The obtained yield should be sufficient to provoke in vivo effects. (c) 2005 European Microbiological Societies. Published by Elsevier B.V. All rights reserved.</p