scholarly journals RpoS-Regulated Genes of Escherichia coli Identified by Random lacZ Fusion Mutagenesis

2004 ◽  
Vol 186 (24) ◽  
pp. 8499-8507 ◽  
Author(s):  
Somalinga R. V. Vijayakumar ◽  
Mark G. Kirchhof ◽  
Cheryl L. Patten ◽  
Herb E. Schellhorn
Keyword(s):  
Escherichia Coli ◽  
Sigma Factor ◽  
Genetic Screen ◽  
The Other ◽  
Alternative Sigma Factor ◽  
Gene Fusions ◽  
Wild Type ◽  
Stress Response Genes ◽  
Independent Gene ◽  
Bacterial Genes

ABSTRACT RpoS is a conserved alternative sigma factor that regulates the expression of many stress response genes in Escherichia coli. The RpoS regulon is large but has not yet been completely characterized. In this study, we report the identification of over 100 RpoS-dependent fusions in a genetic screen based on the differential expression of an operon-lacZ fusion bank in rpoS mutant and wild-type backgrounds. Forty-eight independent gene fusions were identified, including several in well-characterized RpoS-regulated genes, such as osmY, katE, and otsA. Many of the other fusions mapped to genes of unknown function or to genes that were not previously known to be under RpoS control. Based on the homology to other known bacterial genes, some of the RpoS-regulated genes of unknown functions are likely important in nutrient scavenging.

scholarly journals Crl, a Low Temperature-induced Protein inEscherichia coliThat Binds Directly to the Stationary Phase σ Subunit of RNA Polymerase

2004 ◽  
Vol 279 (19) ◽  
pp. 19540-19550 ◽  
Author(s):  
Alexandre Bougdour ◽  
Cécile Lelong ◽  
Johannes Geiselmann
Keyword(s):  
Escherichia Coli ◽  
Stress Response ◽  
Low Temperature ◽  
Rna Polymerase ◽  
Stationary Phase ◽  
Sigma Factor ◽  
Physiological Signals ◽  
Alternative Sigma Factor ◽  
Transcription Rate ◽  
Stress Response Genes

The alternative sigma factor σS(RpoS) ofEscherichia coliRNA polymerase regulates the expression of stationary phase and stress-response genes. σSis also required for the transcription of the cryptic genescsgBAthat encode the subunits of the curli proteins. The expression of thecsgBAgenes is regulated in response to a multitude of physiological signals. In stationary phase, these genes are transcribed by the σSfactor, and expression of the operon is enhanced by the small protein Crl. It has been shown that Crl stimulates the activity of σS, leading to an increased transcription rate of a subset of genes of therpoSregulon in stationary phase. However, the underlying molecular mechanism has remained elusive. We show here that Crl interacts directly with σSand that this interaction promotes binding of the σSholoenzyme (EσS) to thecsgBApromoter. Expression of Crl is increased during the transition from growing to stationary phase. Crl accumulates in stationary phase cells at low temperature (30 °C) but not at 37 °C. We therefore propose that Crl is a second thermosensor, besides DsrA, controlling σSactivity.

scholarly journals Roles of rpoN, fliA,and flgR in Expression of Flagella inCampylobacter jejuni

2001 ◽  
Vol 183 (9) ◽  
pp. 2937-2942 ◽  
Author(s):  
Aparna Jagannathan ◽  
Chrystala Constantinidou ◽  
Charles W. Penn
Keyword(s):  
Campylobacter Jejuni ◽  
Genome Sequence ◽  
Sigma Factor ◽  
Transcriptional Activator ◽  
Alternative Sigma Factor ◽  
Wild Type ◽  
Electron Microscopic ◽  
Global Regulation ◽  
Mutant Strains ◽  
Microscopic Studies

ABSTRACT Three potential regulators of flagellar expression present in the genome sequence of Campylobacter jejuni NCTC 11168, the genes rpoN, flgR, andfliA, which encode the alternative sigma factor ς54, the ς54-associated transcriptional activator FlgR, and the flagellar sigma factor ς28, respectively, were investigated for their role in global regulation of flagellar expression. The three genes were insertionally inactivated inC. jejuni strains NCTC 11168 and NCTC 11828. Electron microscopic studies of the wild-type and mutant strains showed that therpoN and flgR mutants were nonflagellate and that the fliA mutant had truncated flagella. Immunoblotting experiments with the three mutants confirmed the roles of rpoN, flgR, and fliA in the expression of flagellin.

Homologous recombination involving a large heterology in Escherichia coli.

Genetics ◽  
1988 ◽  
Vol 119 (4) ◽  
pp. 759-769
Author(s):  
K Yamamoto ◽  
N Takahashi ◽  
H Yoshikura ◽  
I Kobayashi
Keyword(s):  
Escherichia Coli ◽  
Gene Conversion ◽  
Kanamycin Resistance ◽  
Coli Strain ◽  
The Other ◽  
Reca Gene ◽  
Inverted Repeats ◽  
Crossing Over ◽  
Wild Type ◽  
Parental Allele

Abstract Recombination between two different deletion alleles of a gene (neo) for neomycin and kanamycin resistance was studied in an Escherichia coli sbcA- recB-C- strain. The two homologous regions were in an inverted orientation on the same plasmid molecule. Kanamycin-resistant plasmids were selected and analyzed. The rate of recombination to form kanamycin-resistant plasmids was decreased by mutations in the recE, recF and recJ genes, but was not decreased by a mutation in the recA gene. It was found that these plasmids often possessed one wild-type kanamycin-resistant allele (neo+) while the other neo allele was still in its original (deletion) form. Among kanamycin-resistant plasmids with one wild-type and one parental allele it was often found that the region between the inverted repeats had been flipped (turned around) with respect to sites outside the inverted repeats. These results were interpreted as follows. Gene conversion, analogous to gene conversion in eukaryotic meiosis, is responsible for a unidirectional transfer of information from one neo deletion allele to the other. The flipping of the region between the inverted repeats is interpreted as analogous to the crossing over associated with gene conversion in eukaryotic meiosis. In contrast with a rec+ strain, these products cannot be explained by two rounds of reciprocal crossing over involving a dimeric form as an intermediate. In the accompanying paper we present evidence that gene conversion by double-strand gap repair takes place in the same E. coli strain.

scholarly journals Differential Biological and Adjuvant Activities of Cholera Toxin and Escherichia coli Heat-Labile Enterotoxin Hybrids

2001 ◽  
Vol 69 (3) ◽  
pp. 1528-1535 ◽  
Author(s):  
Christal C. Bowman ◽  
John D. Clements
Keyword(s):  
Escherichia Coli ◽  
Cyclic Amp ◽  
Cholera Toxin ◽  
The Other ◽  
Toxin Gene ◽  
Wild Type ◽  
B Subunit ◽  
Heat Labile ◽  
A Subunit ◽  
Ifn Γ

ABSTRACT Two bacterial products that have been demonstrated to function as mucosal adjuvants are cholera toxin (CT), produced by various strains of Vibrio cholerae, and the heat-labile enterotoxin (LT) produced by some enterotoxigenic strains of Escherichia coli. Although LT and CT have many features in common, they are clearly distinct molecules with biochemical and immunologic differences which make them unique. The goal of this study was to determine the basis for these biological differences by constructing and characterizing chimeric CT-LT molecules. Toxin gene fragments were subcloned to create two constructs, each expressing the enzymatically active A subunit of one toxin and the receptor binding B subunit of the other toxin. These hybrid toxins were purified, and the composition and assembly of CT A subunit (CT-A)-LT B subunit (LT-B) and LT A subunit (LT-A)-CT B subunit (CT-B) were confirmed. Hybrids were evaluated for enzymatic activity, as measured by the accumulation of cyclic AMP in Caco-2 cells, and the enterotoxicity of each toxin was assessed in a patent-mouse assay. The results demonstrated that LT-A–CT-B induces the accumulation of lower levels of cyclic AMP and has less enterotoxicity than either wild-type toxin or the other hybrid. Nonetheless, this hybrid retains adjuvant activity equivalent to or greater than that of either wild-type toxin or the other hybrid when used in conjunction with tetanus toxoid for intranasal immunization of BALB/c mice. Importantly, the ability of LT to induce a type 1 cytokine response was found to be a function of LT-A. Specifically, LT-A–CT-B was able to augment the levels of antigen-specific gamma interferon (IFN-γ) and interleukin 5 to levels comparable to those achieved with native LT, while CT-A–LT-B and native CT both produced lower levels of antigen-specific IFN-γ. Thus, these toxin hybrids possess unique biological characteristics and provide information about the basis for differences in the biological activities observed for CT and LT.

scholarly journals Radiation-Induced Reversion of Transition Mutants

1964 ◽  
Vol 17 (4) ◽  
pp. 907 ◽  
Author(s):  
GW Grigg
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Base Pair ◽  
The Other ◽  
Wild Type ◽  
Lethal Effects ◽  
Reversion Frequency ◽  
X Irradiation ◽  
Radiation Induced ◽  
Adenine Thymine

X-irradiation increased the reversion frequency of two transition mutants of Escherichia coli, one of which (meth-) differed genetically from wild type by an adenine-thymine substitution of a guanine-cytosine base pair, the other (urg-2-) by a guanine-cytosine substitution of an adenine-thymine base pair. The lethal effects of the radiation were greatest when protein synthesis was prevented for a period immediately after irradiation. A period of 30 min at 37�0 was as effective as 22 hr. Irradiation of a saline suspension gave a lower survival of 0�2 times that of bacteria irradiated after being spread on minimal agar plates.

scholarly journals Enhancing Isoprene Production by Genetic Modification of the 1-Deoxy-d-Xylulose-5-Phosphate Pathway inBacillus subtilis

2011 ◽  
Vol 77 (7) ◽  
pp. 2399-2405 ◽  
Author(s):  
Junfeng Xue ◽  
Birgitte K. Ahring
Keyword(s):  
Sigma Factor ◽  
Type Strain ◽  
Wild Type Strain ◽  
Stress Factors ◽  
Alternative Sigma Factor ◽  
Wild Type ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Overexpression Strain ◽  
As Stress

ABSTRACTTo enhance the production of isoprene, a volatile 5-carbon hydrocarbon, in the Gram-positive spore-forming rod-shaped bacteriumBacillus subtilis, 1-deoxy-d-xylulose-5-phosphate synthase (Dxs) and 1-deoxy-d-xylulose-5-phosphate reductoisomerase (Dxr) were overexpressed inB. subtilisDSM 10. For the strain that overexpresses Dxs, the yield of isoprene was increased 40% over that by the wild-type strain. In the Dxr overexpression strain, the level of isoprene production was unchanged. Overexpression of Dxr together with Dxs showed an isoprene production level similar to that of the Dxs overproduction strain. The effects of external factors, such as stress factors including heat (48°C), salt (0.3 M NaCl), ethanol (1%), and oxidative (0.005% H2O2) stress, on isoprene production were further examined. Heat, salt, and H2O2induced isoprene production; ethanol inhibited isoprene production. In addition, induction and repression effects are independent of SigB, which is the general stress-responsive alternative sigma factor of Gram-positive bacteria.

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