Home About us Contact
|
Home About us Contact | ||
|
|
||
Pleiotropic Regulator (pleiotropic + regulator)
Selected AbstractsThe effect of hfq on global gene expression and virulence in Neisseria gonorrhoeaeFEBS JOURNAL, Issue 19 2009Manuela Dietrich Hfq is an RNA chaperone that functions as a pleiotropic regulator for RNA metabolism in bacteria. In several pathogenic bacteria, Hfq contributes indirectly to virulence by binding to riboregulators that modulate the stability or translation efficiency of RNA transcripts. To characterize the role of Hfq in the pathogenicity of Neisseria gonorrhoeae, we generated an N. gonorrhoeae hfq mutant. Infectivity and global changes in gene expression caused by the hfq mutation in N. gonorrhoeae strain MS11 were analyzed. Transcriptional analysis using a custom-made N. gonorrhoeae microarray revealed that 369 ORFs were differentially regulated in the hfq mutant, MS11hfq, in comparison with the wild-type strain (202 were upregulated, and 167 were downregulated). The loss-of-function mutation in hfq led to pleiotropic phenotypic effects, including an altered bacterial growth rate and reduced adherence to epithelial cells. Twitching motility and microcolony formation were not affected. Hfq also appears to play a minor role in inducing the inflammatory response of infected human epithelial cells. Interleukin-8 production was slightly decreased, and activation of c-Jun N-terminal kinase, a mitogen-activated protein kinase, was reduced in MS11hfq- infected epithelial cells in comparison with wild type-infected cells. However, activation of nuclear factor kappa B, extracellular signal-regulated kinase 1/2 and p38 remained unchanged. The data presented suggest that Hfq plays an important role as a post-transcriptional regulator in N. gonorrhoeae strain MS11 but does not contribute significantly to its virulence in cell culture models. [source] Differential identification of Bacillus anthracis from environmental Bacillus species using microarray analysisJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2006J.E. Burton Abstract Aims:, To determine whether microarray analysis could be employed for the differential identification of a range of environmental Bacillus sp. from four strains of Bacillus anthracis. Methods and Results:, Oligonucleotide probes were designed that were specific to virulence factor genes of B. anthracis (pag, lef and cap), the variable number tandem repeat region of the B. anthracis vrrA gene and to the 16S-23S rRNA intergenic transcribed spacer region (ITS) and pleiotropic regulator (plcR) regions of the Bacillus cereus subgroup species. Generic probes were also designed to hybridize with conserved regions of the 16S rRNA genes of Bacillus (as a positive control), Neisseria sp., Pseudomonas sp., Streptococcus sp., Mycobacterium sp. and to all members of the Enterobacteriaceae to allow simultaneous detection of these bacteria. Identification of B. anthracis was found to rely entirely on hybridization of DNA specific to regions of the pag, lef and cap genes. Cross-reaction was observed between B. anthracis and other Bacillus species with all the other Bacillus probes tested. Results obtained using microarray hybridizations were confirmed using conventional microbiological techniques and found to have very high comparability. Conclusions:, Microarray-based assays are an effective method for the identification of B. anthracis from mixed-culture environmental samples without problems of false-positivity that have been observed with conventional PCR assays. Significance and Impact of the Study:, Identification of environmental Bacillus sp. by conventional PCR is prone to potential for reporting false-positives. This study provides a method for the exclusion of such isolates. [source] Transcription regulation of the Saccharomyces cerevisiae PIS1 gene by inositol and the pleiotropic regulator, Ume6pMOLECULAR MICROBIOLOGY, Issue 6 2008Niketa M. Jani Summary In Saccharomyces cerevisiae, transcription of most of the phospholipid biosynthetic genes (e.g. INO1, CHO1, CHO2 and OPI3) is repressed by growth in the presence of inositol and choline and derepressed in their absence. This regulation requires the Ino2p and Ino4p activators and the Opi1p repressor. The PIS1 structural gene is required for the synthesis of the essential lipid phosphatidylinositol. Previous reports show that PIS1 expression is uncoupled from inositol/choline regulation, but is regulated by carbon source, hypoxia and zinc. However, in this study we found that the expression of PIS1 is induced twofold by inositol. This regulation did not require Ino2p and Ino4p, although Ino4p was required for full expression. Ino4p is a basic helix-loop-helix protein that requires a binding partner. Curiously, none of the other basic helix-loop-helix proteins affected PIS1 expression. Inositol induction did require another general regulator of phospholipid biosynthesis, Ume6p. Ume6p was found to be a positive regulator of PIS1 gene expression. Ume6p, and several associated factors, were required for inositol-mediated induction and chromatin immunoprecipitation analysis showed that Ume6p directly regulates PIS1 expression. Thus, we demonstrate novel regulation of the PIS1 gene by Ume6p. [source] Deciphering regulatory mechanisms for secondary metabolite production in the myxobacterium Sorangium cellulosum So ce56MOLECULAR MICROBIOLOGY, Issue 6 2007Shwan Rachid Summary Sorangium cellulosum strains produce approximately 50% of the biologically active secondary metabolites known from myxobacteria. These metabolites include several compounds of biotechnological importance such as the epothilones and chivosazols, which, respectively, stabilize the tubulin and actin skeletons of eukaryotic cells. S. cellulosum is characterized by its slow growth rate, and natural products are typically produced in low yield. In this study, biomagnetic bead separation of promoter-binding proteins and subsequent inactivation experiments were employed to identify the chivosazol regulator, ChiR, as a positive regulator of chivosazol biosynthesis in the genome-sequenced strain So ce56. Overexpression of chiR under the control of T7A1 promoter in a merodiploid mutant resulted in fivefold overproduction of chivosazol in a kinetic shake flask experiment, and 2.5-fold overproduction by fermentation. Using quantitative reverse transcription PCR and gel shift experiments employing heterologously expressed ChiR, we have shown that transcription of the chivosazol biosynthetic genes (chiA,chiF) is directly controlled by this protein. In addition, we have demonstrated that ChiR serves as a pleiotropic regulator in S. cellulosum, because mutant strains lack the ability to develop into regular fruiting bodies. [source] Oligopeptide permease is required for expression of the Bacillus thuringiensis plcR regulon and for virulenceMOLECULAR MICROBIOLOGY, Issue 4 2001Myriam Gominet PlcR is a pleiotropic regulator of virulence factors in the insect pathogen Bacillus thuringiensis and in the opportunistic human pathogen Bacillus cereus. It activates the transcription of at least 15 genes encoding extracellular proteins, including phospholipases C, proteases and enterotoxins. Expression of the plcR gene is autoregulated and activated at the onset of stationary phase. Here, we used mini-Tn10 transposition to generate a library of B. thuringiensis mutants, with the goal of characterizing genes involved in the expression of the plcR gene. Three mutant strains were identified carrying distinct mini-Tn10 insertions. The mutations impaired plcR expression and caused a deficient haemolytic phenotype, similar to the phenotype of a B. thuringiensis strain in which the plcR gene had been disrupted. The insertion sites of the three mini-Tn10 transposons mapped in a five-gene operon encoding polypeptides homologous to the components of the oligopeptide permease (Opp) system of Bacillus subtilis, and with a similar structural organization. By analogy, the five B. thuringiensis genes were designated oppA, B, C, D and F. In vitro disruption of the B. thuringiensis oppB gene reproduced the effect of the mini-Tn10 insertions (i.e. the loss of haemolytic activity) and reduced the virulence of the strain against insects. These phenotypes are similar to those of a ,plcR mutant. Opp is required for the import of small peptides into the cell. Therefore, plcR expression might be activated at the onset of stationary phase by the uptake of a signalling peptide acting as a quorum-sensing effector. The opp mutations impaired the sporulation efficiency of B. thuringiensis when the cells were cultured in LB medium. Thus, Opp is on the pathway that ultimately regulates Spo0A phosphorylation, as is the case in B. subtilis. However, analysis of plcR expression in ,oppB, ,spo0A and ,oppB,spo0A mutants indicates that Opp is required for plcR expression via a Spo0A-independent mechanism. [source] Orexins and the regulation of the hypothalamic-pituitary-testicular axisACTA PHYSIOLOGICA, Issue 3 2010M. Nurmio Abstract Orexins (OX), OX-A and OX-B, were initially identified as hypothalamic neuropeptides primarily involved in the control of food intake and states of arousal. Thereafter, orexins have been substantiated as putative pleiotropic regulators of a wide diversity of biological systems, including different neuroendocrine axes. Among the latter, compelling experimental evidence has recently been documented that orexins, mainly OX-A, may act at different levels of the hypothalamic-pituitary-gonadal (HPG) axis to modulate reproductive function. These actions are likely to include regulatory effects on the hypothalamic centres governing the HPG axis, as well as direct actions at the gonadal level. We review herein the experimental evidence, gathered in recent years, supporting a reproductive ,facet' of orexins, with special emphasis on our current knowledge of their patterns of expression and potential functional roles in the testis. Overall, the available data strongly suggest that, by acting at different levels of the HPG axis, orexins may operate as putative neuroendocrine and autocrine/paracrine regulators of gonadal function. [source] | ||||||||||