scholarly journals Identification, cloning, and expression of the Escherichia coli pyrazinamidase and nicotinamidase gene, pncA.

1996 ◽  
Vol 40 (6) ◽  
pp. 1426-1431 ◽  
Author(s):  
R Frothingham ◽  
W A Meeker-O'Connell ◽  
E A Talbot ◽  
J W George ◽  
K N Kreuzer
Keyword(s):  
Escherichia Coli ◽  
Genetic Locus ◽  
Fold Increase ◽  
Pyridine Nucleotide ◽  
Cloning And Expression ◽  
Insertion Mutant ◽  
Activity Levels ◽  
Multicopy Plasmid ◽  
Wild Type ◽  
E Coli

Pyrazinamide (PZA) is one of the three most important drugs for treatment of Mycobacterium tuberculosis infections. The antibacterial activity of PZA requires a bacterial enzyme, pyrazinamidase (PZAase), which hydrolyzes PZA to form pyrazinoic acid and ammonia. Most PZA-resistant clinical M. tuberculosis isolates lack PZAase activity. With the goal of eventually identifying and characterizing the M.tuberculosis PZAase gene, we began with the more tractable organism, Escherichia coli, which also has PZAase activity. We screened a transposon-generated E. coli insertion mutant library, using a qualitative PZAase assay. Two PZAase-negative mutants out of 4,000 colonies screened were identified. In each mutant, the transposon interrupted the same 639-bp open reading frame (ORF), ORF1. The expression of ORF1 on a multicopy plasmid complemented a PZAase-negative mutant, leading to PZAase activity levels approximately 10-fold greater than those of the wild type. PZA has a structure similar to that of nicotinamide, a pyridine nucleotide cycle intermediate, so we tested our strains for nicotinamidase activity (EC 3.5.1.19) (genetic locus pncA). The construct with multiple plasmid copies of ORF1 had an approximately 10-fold increase in levels of nicotinamidase activity. This overexpressing strain could utilize nicotinamide as a sole nitrogen source, through wild-type E. coli cannot. We conclude that a single E. coli enzyme accounts for both PZAase and nicotinamidase activities and that ORF1 is the E.coli PZAase and nicotinamidase gene, pncA.

scholarly journals 16S rRNA Mutations That Confer Tetracycline Resistance in Helicobacter pylori Decrease Drug Binding in Escherichia coli Ribosomes

2005 ◽  
Vol 187 (11) ◽  
pp. 3708-3712 ◽  
Author(s):  
Lisa Nonaka ◽  
Sean R. Connell ◽  
Diane E. Taylor
Keyword(s):  
Escherichia Coli ◽  
Helicobacter Pylori ◽  
16S Rrna ◽  
Binding Site ◽  
Tetracycline Resistance ◽  
Drug Binding ◽  
Multicopy Plasmid ◽  
Wild Type ◽  
E Coli ◽  
H Pylori

ABSTRACT Tetracycline resistance in clinical isolates of Helicobacter pylori has been associated with nucleotide substitutions at positions 965 to 967 in the 16S rRNA. We constructed mutants which had different sequences at 965 to 967 in the 16S rRNA gene present on a multicopy plasmid in Escherichia coli strain TA527, in which all seven rrn genes were deleted. The MICs for tetracycline of all mutants having single, double, or triple substitutions at the 965 to 967 region that were previously found in highly resistant H. pylori isolates were higher than that of the mutant exhibiting the wild-type sequence of tetracycline-susceptible H. pylori. The MIC of the mutant with the 965TTC967 triple substitution was 32 times higher than that of the E. coli mutant with the 965AGA967 substitution present in wild-type H. pylori. The ribosomes extracted from the tetracycline-resistant E. coli 965TTC967 variant bound less tetracycline than E. coli with the wild-type H. pylori sequence at this region. The concentration of tetracycline bound to the ribosome was 40% that of the wild type. The results of this study suggest that tetracycline binding to the primary binding site (Tet-1) of the ribosome at positions 965 to 967 is influenced by its sequence patterns, which form the primary binding site for tetracycline.

scholarly journals Identification and Characterization of a New Lipoprotein, NlpI, in Escherichia coli K-12

1999 ◽  
Vol 181 (14) ◽  
pp. 4318-4325 ◽  
Author(s):  
Masaru Ohara ◽  
Henry C. Wu ◽  
Krishnan Sankaran ◽  
Paul D. Rick
Keyword(s):  
Escherichia Coli ◽  
Direct Consequence ◽  
Insertion Mutant ◽  
Polynucleotide Phosphorylase ◽  
Wild Type ◽  
E Coli ◽  
K 12 ◽  
Identification And Characterization ◽  
Lines Of Evidence

ABSTRACT We report here the identification of a new lipoprotein, NlpI, inEscherichia coli K-12. The NlpI structural gene (nlpI) is located between the genes pnp(polynucleotide phosphorylase) and deaD (RNA helicase) at 71 min on the E. coli chromosome. The nlpI gene encodes a putative polypeptide of approximately 34 kDa, and multiple lines of evidence clearly demonstrate that NlpI is indeed a lipoprotein. An nlpI::cm mutation rendered growth of the cells osmotically sensitive, and incubation of the insertion mutant at an elevated temperature resulted in the formation of filaments. The altered phenotype of the mutant was a direct consequence of the mutation in nlpI, since it was complemented by the wild-type nlpI gene alone. Overexpression of the unaltered nlpI gene in wild-type cells resulted in the loss of the rod morphology and the formation of single prolate ellipsoids and pairs of prolate ellipsoids joined by partial constrictions. NlpI may be important for an as-yet-undefined step in the overall process of cell division.

Evolving improved Synechococcus Rubisco functional expression in Escherichia coli

2008 ◽  
Vol 414 (2) ◽  
pp. 205-214 ◽  
Author(s):  
Oliver Mueller-Cajar ◽  
Spencer M. Whitney
Keyword(s):  
Escherichia Coli ◽  
Large Subunit ◽  
Fold Increase ◽  
Functional Expression ◽  
Kinetic Properties ◽  
Selection System ◽  
Wild Type ◽  
Bisphosphate Carboxylase ◽  
E Coli ◽  
Enhanced Expression

The photosynthetic CO2-fixing enzyme Rubisco [ribulose-P2 (D-ribulose-1,5-bisphosphate) carboxylase/oxygenase] has long been a target for engineering kinetic improvements. Towards this goal we used an RDE (Rubisco-dependent Escherichia coli) selection system to evolve Synechococcus PCC6301 Form I Rubisco under different selection pressures. In the fastest growing colonies, the Rubisco L (large) subunit substitutions I174V, Q212L, M262T, F345L or F345I were repeatedly selected and shown to increase functional Rubisco expression 4- to 7-fold in the RDE and 5- to 17-fold when expressed in XL1-Blue E. coli. Introducing the F345I L-subunit substitution into Synechococcus PCC7002 Rubisco improved its functional expression 11-fold in XL1-Blue cells but could not elicit functional Arabidopsis Rubisco expression in the bacterium. The L subunit substitutions L161M and M169L were complementary in improving Rubisco yield 11-fold, whereas individually they improved yield ∼5-fold. In XL1-Blue cells, additional GroE chaperonin enhanced expression of the I174V, Q212L and M262T mutant Rubiscos but engendered little change in the yield of the more assembly-competent F345I or F345L mutants. In contrast, the Rubisco chaperone RbcX stimulated functional assembly of wild-type and mutant Rubiscos. The kinetic properties of the mutated Rubiscos varied with noticeable reductions in carboxylation and oxygenation efficiency accompanying the Q212L mutation and a 2-fold increase in Kribulose-P2 (KM for the substrate ribulose-P2) for the F345L mutant, which was contrary to the ∼30% reductions in Kribulose-P2 for the other mutants. These results confirm the RDE systems versatility for identifying mutations that improve functional Rubisco expression in E. coli and provide an impetus for developing the system to screen for kinetic improvements.

scholarly journals Function of the ςE Regulon in Dead-Cell Lysis in Stationary-Phase Escherichia coli

2000 ◽  
Vol 182 (18) ◽  
pp. 5231-5237 ◽  
Author(s):  
Takeshi Nitta ◽  
Hiroshi Nagamitsu ◽  
Masayuki Murata ◽  
Hanae Izu ◽  
Mamoru Yamada
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Cell Lysis ◽  
Dead Cell ◽  
Multicopy Plasmid ◽  
Wild Type ◽  
E Coli ◽  
Intracellular Proteins ◽  
In The Wild ◽  
Cloned Gene

ABSTRACT Elevation of active ςE levels in Escherichia coli by either repressing the expression of rseAencoding an anti-ςE factor or cloning rpoE in a multicopy plasmid, led to a large decrease in the number of dead cells and the accumulation of cellular proteins in the medium in the stationary phase. The numbers of CFU, however, were nearly the same as those of the wild type or cells devoid of the cloned gene. In the wild-type cells, rpoE expression was increased in the stationary phase and a low-level release of intracellular proteins was observed. These results suggest that dead cell lysis in stationary-phase E. coli occurs in a ςE-dependent fashion. We propose there is a novel physiological function of the ςE regulon that may guarantee cell survival in prolonged stationary phase by providing nutrients from dead cells for the next generation.

A gene between polA and glnA retards growth of Escherichia coli when present in multiple copies: physiological effects of the gene for spot 42 RNA

1982 ◽  
Vol 152 (3) ◽  
pp. 1196-1210
Author(s):  
P W Rice ◽  
J E Dahlberg
Keyword(s):  
Escherichia Coli ◽  
Single Gene ◽  
Fold Increase ◽  
Growth Conditions ◽  
Multicopy Plasmid ◽  
Coding Region ◽  
E Coli ◽  
6S Rna ◽  
Dna Fragment ◽  
Casamino Acids

We have isolated the single gene for spot 42 RNA of Escherichia coli on a 20-kilobase DNA fragment. Physical characterization of this cloned DNA fragment showed that it is homologous to a region at 86 min on the genetic map and extends from the 23S to 5S rRNA coding region of rrnA to the coding region of glnA, the gene for glutamine synthetase. Other genes included on this cloned DNA fragment are polA, ntrC (glnG), and ntrB (glnL). E coli cells transformed with a multicopy plasmid clone of the gene for spot 42 RNA had about a 10-fold increase in the amount of spot 42 RNA they contained. The amount of 6S RNA in these cells was increased about twofold, although the gene for 6S RNA was not located on this plasmid or on the larger 20-kilobase fragment. Presence of this multicopy plasmid also affected the growth of cells. The generation time was increased under a variety of growth conditions, especially when cells were grown in medium with succinate as the carbon source. In addition, some strains of E. coli which have multicopy plasmids carrying the gene for spot 42 RNA were unable to respond normally to a shift into richer medium: upon upshift from minimal glucose to LB broth or minimal glucose plus 1% Casamino Acids, there was a 3- to 4-h lag before the culture adapted to the new medium. More than 90% of the cells in such cultures stopped dividing, although they remained viable. The plating efficiency of minimal-glucose-grown cells was 100-fold less on rich media than on minimal glucose medium. One revertant was isolated which regained the phenotype of pBR322-transformed cells. Analysis of this strain showed that the plasmid it contained had an insertion of an IS1 element into the 5' end of the coding region for the gene for spot 42 RNA.

scholarly journals degS Is Necessary for Virulence and Is among Extraintestinal Escherichia coli Genes Induced in Murine Peritonitis

2003 ◽  
Vol 71 (6) ◽  
pp. 3088-3096 ◽  
Author(s):  
Peter Redford ◽  
Paula L. Roesch ◽  
Rodney A. Welch
Keyword(s):  
Escherichia Coli ◽  
Urinary Tract Infection ◽  
Urinary Tract ◽  
Tract Infection ◽  
Luria Bertani ◽  
Broth Culture ◽  
Wild Type ◽  
E Coli ◽  
Virulence Attenuation

ABSTRACT Extraintestinal Escherichia coli strains cause meningitis, sepsis, urinary tract infection, and other infections outside the bowel. We examined here extraintestinal E. coli strain CFT073 by differential fluorescence induction. Pools of CFT073 clones carrying a CFT073 genomic fragment library in a promoterless gfp vector were inoculated intraperitoneally into mice; bacteria were recovered by lavage 6 h later and then subjected to fluorescence-activated cell sorting. Eleven promoters were found to be active in the mouse but not in Luria-Bertani (LB) broth culture. Three are linked to genes for enterobactin, aerobactin, and yersiniabactin. Three others are linked to the metabolic genes metA, gltB, and sucA, and another was linked to iha, a possible adhesin. Three lie before open reading frames of unknown function. One promoter is associated with degS, an inner membrane protease. Mutants of the in vivo-induced loci were tested in competition with the wild type in mouse peritonitis. Of the mutants tested, only CFT073 degS was found to be attenuated in peritoneal and in urinary tract infection, with virulence restored by complementation. CFT073 degS shows growth similar to that of the wild type at 37°C but is impaired at 43°C or in 3% ethanol LB broth at 37°C. Compared to the wild type, the mutant shows similar serum survival, motility, hemolysis, erythrocyte agglutination, and tolerance to oxidative stress. It also has the same lipopolysaccharide appearance on a silver-stained gel. The basis for the virulence attenuation is unclear, but because DegS is needed for σE activity, our findings implicate σE and its regulon in E. coli extraintestinal pathogenesis.

scholarly journals Enhancement of the Efficiency of Secretion of Heterologous Lipase in Escherichia coli by Directed Evolution of the ABC Transporter System

2005 ◽  
Vol 71 (7) ◽  
pp. 3468-3474 ◽  
Author(s):  
Gyeong Tae Eom ◽  
Jae Kwang Song ◽  
Jung Hoon Ahn ◽  
Yeon Soo Seo ◽  
Joon Shick Rhee
Keyword(s):  
Escherichia Coli ◽  
Directed Evolution ◽  
Abc Transporter ◽  
Microtiter Plate ◽  
Single Amino Acid ◽  
Wild Type ◽  
E Coli ◽  
Single Amino Acid Change ◽  
Secretion Efficiency

ABSTRACT The ABC transporter (TliDEF) from Pseudomonas fluorescens SIK W1, which mediated the secretion of a thermostable lipase (TliA) into the extracellular space in Escherichia coli, was engineered using directed evolution (error-prone PCR) to improve its secretion efficiency. TliD mutants with increased secretion efficiency were identified by coexpressing the mutated tliD library with the wild-type tliA lipase in E. coli and by screening the library with a tributyrin-emulsified indicator plate assay and a microtiter plate-based assay. Four selected mutants from one round of error-prone PCR mutagenesis, T6, T8, T24, and T35, showed 3.2-, 2.6-, 2.9-, and 3.0-fold increases in the level of secretion of TliA lipase, respectively, but had almost the same level of expression of TliD in the membrane as the strain with the wild-type TliDEF transporter. These results indicated that the improved secretion of TliA lipase was mediated by the transporter mutations. Each mutant had a single amino acid change in the predicted cytoplasmic regions in the membrane domain of TliD, implying that the corresponding region of TliD was important for the improved and successful secretion of the target protein. We therefore concluded that the efficiency of secretion of a heterologous protein in E. coli can be enhanced by in vitro engineering of the ABC transporter.

scholarly journals Engineering Desiccation Tolerance inEscherichia coli

2000 ◽  
Vol 66 (4) ◽  
pp. 1680-1684 ◽  
Author(s):  
Daniela Billi ◽  
Deborah J. Wright ◽  
Richard F. Helm ◽  
Todd Prickett ◽  
Malcolm Potts ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Phase Transition ◽  
Freeze Drying ◽  
Fold Increase ◽  
Inescherichia Coli ◽  
Vibration Frequencies ◽  
Wild Type ◽  
Air Drying ◽  
Phase Transition Temperatures ◽  
Cell Dehydration

ABSTRACT Recombinant sucrose-6-phosphate synthase (SpsA) was synthesized inEscherichia coli BL21DE3 by using the spsA gene of the cyanobacterium Synechocystis sp. strain PCC 6803. Transformants exhibited a 10,000-fold increase in survival compared to wild-type cells following either freeze-drying, air drying, or desiccation over phosphorus pentoxide. The phase transition temperatures and vibration frequencies (PO stretch) in phospholipids suggested that sucrose maintained membrane fluidity during cell dehydration.

scholarly journals Quorum Sensing Is a Global Regulatory Mechanism in Enterohemorrhagic Escherichia coli O157:H7

2001 ◽  
Vol 183 (17) ◽  
pp. 5187-5197 ◽  
Author(s):  
Vanessa Sperandio ◽  
Alfredo G. Torres ◽  
Jorge A. Girón ◽  
James B. Kaper
Keyword(s):  
Escherichia Coli ◽  
Quorum Sensing ◽  
Type Strain ◽  
Wild Type Strain ◽  
Regulatory Mechanism ◽  
Sos Response ◽  
Enterohemorrhagic Escherichia Coli ◽  
Trna Genes ◽  
Wild Type ◽  
E Coli

ABSTRACT Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is responsible for outbreaks of bloody diarrhea and hemolytic-uremic syndrome in many countries. EHEC virulence mechanisms include the production of Shiga toxins (Stx) and formation of attaching and effacing (AE) lesions on intestinal epithelial cells. We recently reported that genes involved in the formation of the AE lesion were regulated by quorum sensing through autoinducer-2, which is synthesized by the product of the luxS gene. In this study we hybridized an E. coli gene array with cDNA synthesized from RNA that was extracted from EHEC strain 86-24 and its isogenicluxS mutant. We observed that 404 genes were regulated by luxS at least fivefold, which comprises approximately 10% of the array genes; 235 of these genes were up-regulated and 169 were down-regulated in the wild-type strain compared to in theluxS mutant. Down-regulated genes included several involved in cell division, as well as ribosomal and tRNA genes. Consistent with this pattern of gene expression, theluxS mutant grows faster than the wild-type strain (generation times of 37.5 and 60 min, respectively, in Dulbecco modified Eagle medium). Up-regulated genes included several involved in the expression and assembly of flagella, motility, and chemotaxis. Using operon::lacZ fusions to class I, II, and III flagellar genes, we were able to confirm this transcriptional regulation. We also observed fewer flagella by Western blotting and electron microscopy and decreased motility halos in semisolid agar in the luxS mutant. The average swimming speeds for the wild-type strain and the luxS mutant are 12.5 and 6.6 μm/s, respectively. We also observed an increase in the production of Stx due to quorum sensing. Genes encoding Stx, which are transcribed along with λ-like phage genes, are induced by an SOS response, and genes involved in the SOS response were also regulated by quorum sensing. These results indicate that quorum sensing is a global regulatory mechanism for basic physiological functions of E. coli as well as for virulence factors.

scholarly journals A Pathoadaptive Deletion in an Enteroaggregative Escherichia coli Outbreak Strain Enhances Virulence in a Caenorhabditis elegans Model

2010 ◽  
Vol 78 (9) ◽  
pp. 4068-4076 ◽  
Author(s):  
Jennifer Hwang ◽  
Lisa M. Mattei ◽  
Laura G. VanArendonk ◽  
Philip M. Meneely ◽  
Iruka N. Okeke
Keyword(s):  
Escherichia Coli ◽  
Caenorhabditis Elegans ◽  
Epithelial Cells ◽  
Genetic Material ◽  
Decarboxylase Activity ◽  
Multicopy Plasmid ◽  
Lysine Decarboxylase ◽  
Outbreak Strain ◽  
E Coli ◽  
C Elegans

ABSTRACT Enteroaggregative Escherichia coli (EAEC) strains are important diarrheal pathogens. EAEC strains are defined by their characteristic stacked-brick pattern of adherence to epithelial cells but show heterogeneous virulence and have different combinations of adhesin and toxin genes. Pathoadaptive deletions in the lysine decarboxylase (cad) genes have been noted among hypervirulent E. coli subtypes of Shigella and enterohemorrhagic E. coli. To test the hypothesis that cad deletions might account for heterogeneity in EAEC virulence, we developed a Caenorhabditis elegans pathogenesis model. Well-characterized EAEC strains were shown to colonize and kill C. elegans, and differences in virulence could be measured quantitatively. Of 49 EAEC strains screened for lysine decarboxylase activity, 3 tested negative. Most notable is isolate 101-1, which was recovered in Japan, from the largest documented EAEC outbreak. EAEC strain 101-1 was unable to decarboxylate lysine in vitro due to deletions in cadA and cadC, which, respectively, encode lysine decarboxylase and a transcriptional activator of the cadAB genes. Strain 101-1 was significantly more lethal to C. elegans than control strain OP50. Lethality was attenuated when the lysine decarboxylase defect was complemented from a multicopy plasmid and in single copy. In addition, restoring lysine decarboxylase function produced derivatives of 101-1 deficient in aggregative adherence to cultured human epithelial cells. Lysine decarboxylase inactivation is pathoadapative in an important EAEC outbreak strain, and deletion of cad genes could produce hypervirulent EAEC lineages in the future. These results suggest that loss, as well as gain, of genetic material can account for heterogeneous virulence among EAEC strains.

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