scholarly journals Mutations That Activate the Silent bgl Operon of Escherichia coli Confer a Growth Advantage in Stationary Phase

2005 ◽  
Vol 187 (23) ◽  
pp. 7912-7917 ◽  
Author(s):  
Ranjna Madan ◽  
Roberto Kolter ◽  
S. Mahadevan
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Genetic System ◽  
Wild Type ◽  
Evolutionary Advantage ◽  
Type Strains

ABSTRACT Wild-type strains of Escherichia coli are unable to utilize aromatic β-glucosides such as arbutin and salicin because the major genetic system that encodes the functions for their catabolism, the bgl operon, is silent and uninducible. We show that strains that carry an activated bgl operon exhibit a growth advantage over the wild type in stationary phase in the presence of the rpoS819 allele that causes attenuated rpoS regulon expression. Our results indicate a possible evolutionary advantage in retaining the silent bgl operon by wild-type bacteria.

scholarly journals Plasmid DNA Supercoiling and Gyrase Activity in Escherichia coli Wild-Type and rpoS Stationary-Phase Cells

2003 ◽  
Vol 185 (3) ◽  
pp. 1097-1100 ◽  
Author(s):  
Yazmid Reyes-Domínguez ◽  
Gabriel Contreras-Ferrat ◽  
Jesús Ramírez-Santos ◽  
Jorge Membrillo-Hernández ◽  
M. Carmen Gómez-Eichelmann
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Plasmid Dna ◽  
Bimodal Distribution ◽  
Dna Supercoiling ◽  
Wild Type

ABSTRACT Stationary-phase cells displayed a distribution of relaxed plasmids and had the ability to recover plasmid supercoiling as soon as nutrients became available. Preexisting gyrase molecules in these cells were responsible for this recovery. Stationary-phase rpoS cells showed a bimodal distribution of plasmids and failed to supercoil plasmids after the addition of nutrients, suggesting that rpoS plays a role in the regulation of plasmid topology during the stationary phase.

scholarly journals Natural Genetic Transformation of Clinical Isolates of Escherichia coli in Urine and Water

2002 ◽  
Vol 68 (1) ◽  
pp. 440-443 ◽  
Author(s):  
Markus Woegerbauer ◽  
Bernard Jenni ◽  
Florian Thalhammer ◽  
Wolfgang Graninger ◽  
Heinz Burgmann
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Current Knowledge ◽  
Antibiotic Resistance Genes ◽  
Aquatic Environments ◽  
Wild Type ◽  
E Coli ◽  
Naturally Occurring ◽  
Natural Genetic Transformation ◽  
Type Strains

ABSTRACT Transfer of plasmid-borne antibiotic resistance genes in Escherichia coli wild-type strains is possible by transformation under naturally occurring conditions in oligotrophic, aquatic environments containing physiologic concentrations of calcium. In contrast, transformation is suppressed in nitrogen-rich body fluids like urine, a common habitat of uropathogenic strains. Current knowledge indicates that transformation of these E. coli wild-type strains is of no relevance for the acquisition of resistance in this clinically important environment.

DNA cytosine methyltransferase enhances viability during prolonged stationary phase in Escherichia coli

2020 ◽  
Vol 367 (20) ◽  
Author(s):  
Kevin T Militello ◽  
Lara Finnerty-Haggerty ◽  
Ooha Kambhampati ◽  
Rebecca Huss ◽  
Rachel Knapp
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Wild Type ◽  
Bacterial Physiology ◽  
Phase Competition ◽  
Cytosine Methyltransferase ◽  
The Impact ◽  
Restriction Modification ◽  
Restriction Modification Systems

ABSTRACT In Escherichia coli, DNA cytosine methyltransferase (Dcm) methylates the second cytosine in the sequence 5′CCWGG3′ generating 5-methylcytosine. Dcm is not associated with a cognate restriction enzyme, suggesting Dcm impacts facets of bacterial physiology outside of restriction-modification systems. Other than gene expression changes, there are few phenotypes that have been identified in strains with natural or engineered Dcm loss, and thus Dcm function has remained an enigma. Herein, we demonstrate that Dcm does not impact bacterial growth under optimal and selected stress conditions. However, Dcm does impact viability in long-term stationary phase competition experiments. Dcm+ cells outcompete cells lacking dcm under different conditions. Dcm knockout cells have more RpoS-dependent HPII catalase activity than wild-type cells. Thus, the impact of Dcm on stationary phase may involve changes in RpoS activity. Overall, our data reveal a new role for Dcm during long-term stationary phase.

A Stable 44S Intermediate in the Autodigestion of 50S Ribosomal Subunits

1971 ◽  
Vol 29 ◽  
pp. 430-431
Author(s):  
John H. Nisbet ◽  
Henry S. Slayter
Keyword(s):  
Escherichia Coli ◽  
Molecular Weight ◽  
Ribosomal Rna ◽  
Gel Electrophoresis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Ribosomal Subunit ◽  
Wild Type ◽  
Ribosomal Subunits ◽  
Type Strains

Wild - type strains of Escherichia coli are known to contain as many as four endogenous nucleases (Ref. 1). These are commonly found associated with the ribosomes after extraction from the cell, but may be removed, with the exception of RNase IV, by washing the ribosomes in NH4Cl (at 0.2 M and higher concentrations). We have examined the effect of these nucleases on the 50S ribosomal subunit of one wild-type strain, K12 (Hfr 3000), by incubating the unwashed particles at 37° in the presence of varying magnesium concentrations.At 10-4 molar magnesium (slower at 10-3 molar), the 50S particle is converted to a species sedimenting at about 44S. About 20% of the total O.D260 is liberated at the same time. Continued incubation leads to the release of more O.D260 material while the RNA remaining in the 44S (Fig. 1) particle is progressively cleaved, eventually to the point where it consists of one principal fragment of molecular weight 0.42 x 106 daltons and several lesser fragments. The ribosomal RNA and proteins have been characterized by acrylamide gel electrophoresis.

Colicins G and H and their host strains

1991 ◽  
Vol 37 (10) ◽  
pp. 751-757 ◽  
Author(s):  
D. E. Bradley
Keyword(s):  
Escherichia Coli ◽  
Key Words ◽  
Side Chains ◽  
Human Origin ◽  
Wild Type ◽  
E Coli ◽  
Molecular Weights ◽  
Protein Receptors ◽  
Type Strains ◽  
Host Strains

Escherichia coli strains CA46(pColG) and CA58(pColH) each apparently synthesized two generally similar bactericidal colicin proteins whose molecular weights were approximately 5 500 and 100 000. These proteins were more resistant to trypsin than representative colicins A, D, E1, and V. The smooth wild-type strains harbouring plasmids pColG and pColH were serotyped O169:NM and O30:NM, respectively, being typically associated with nonpathogenic E. coli of human origin. Rough and semirough variants, which were selected using resistance to novobiocin, were intrinsically insensitive to almost as many colicins (10 tested) as their parents. For this reason the wild-type strains would not be useful for identifying colicins G and H on the basis of immunity. The O antigenic side chains of both wild-type strains shielded three of the six bacteriophage protein receptors tested. Key words: colicin, protein, plasmid, O antigen, bacteriophage.

scholarly journals Acquisition and Maintenance of Enterotoxin Plasmids in Wild-type Strains of Escherichia coli

Microbiology ◽  
1983 ◽  
Vol 129 (10) ◽  
pp. 3111-3120 ◽  
Author(s):  
S. M. Scotland ◽  
N. P. Day ◽  
B. Rowe
Keyword(s):  
Escherichia Coli ◽  
Wild Type ◽  
Type Strains

Phase variation of F1651 (Prs-like) fimbriae from Escherichia coli causing septicaemia in animals

2000 ◽  
Vol 46 (12) ◽  
pp. 1101-1107 ◽  
Author(s):  
Josée Harel ◽  
France Daigle ◽  
Céline Forget ◽  
Marie-Catherine Tessier ◽  
Cécile Crost ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Gene Cluster ◽  
Regulatory Region ◽  
Phase Variation ◽  
Immunofluorescence Staining ◽  
Wild Type ◽  
Young Pigs ◽  
Dam Methylation ◽  
Structural Subunit ◽  
Type Strains

Escherichia coli O115:F165 strains are associated with septicaemia in young pigs and synthesize fimbriae involved in virulence, designated as F1651. F1651 fimbriae belong to the P fimbrial family and are encoded by the foo gene cluster. The foo regulatory region of strain 5131 possesses characteristics similar to that of members of the P regulatory family, including papI and papB homologues, and two GATC sites separated by 102 bp, targets of differential Dam methylation. In wild-type strains, the synthesis of F1651 is repressed by leucine and the fimbriae undergo phase variation. Immunofluorescence staining showed that phase variation of F1651 results in a majority of cells (98%) in the ON phase, in contrast with phase variation of other members of this regulatory family, for which the majority of the cells are in the OFF state. Using a translational fusion in strain 5131 between phoA and fooA, encoding for the major structural subunit of F1651, it was shown that leucine inhibits the OFF to ON switch and modulates the basal transcription of the foo operon.Key words: Escherichia coli, fimbriae, phase variation, regulation, septicaemia.

scholarly journals Effect on solute size on diffusion rates through the transmembrane pores of the outer membrane of Escherichia coli.

1981 ◽  
Vol 77 (2) ◽  
pp. 121-135 ◽  
Author(s):  
H Nikaido ◽  
E Y Rosenberg
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Specific Class ◽  
Wild Type ◽  
Intact Cells ◽  
E Coli ◽  
Low Concentrations ◽  
Transmembrane Pores ◽  
Diffusion Rates ◽  
Type Strains

Nutrients usually cross the outer membrane of Escherichia coli by diffusion through water-filled channels surrounded by a specific class of protein, porins. In this study, the rates of diffusion of hydrophilic nonelectrolytes, mostly sugars and sugar alcohols, through the porin channels were determined in two systems, (a) vesicles reconstituted from phospholipids and purified porin and (b) intact cells of mutant strains that produce many fewer porin molecules than wild-type strains. The diffusion rates were strongly affected by the size of the solute, even when the size was well within the "exclusion limit" of the channel. In both systems, hexoses and hexose disaccharides diffused through the channel at rates 50-80% and 2-4%, respectively, of that of a pentose, arabinose. Application of the Renkin equation to these data led to the estimate that the pore radius is approximately 0.6 nm, if the pore is assumed to be a hollow cylinder. The results of the study also show that the permeability of the outer membrane of the wild-type E. coli cell to glucose and lactose can be explained by the presence of porin channels, that a significant fraction of these channels must be functional or "open" under our conditions of growth, and that even 10(5) channels per cell could become limiting when E. coli tries to grow at a maximal rate on low concentrations of slowly penetrating solutes, such as disaccharides.

scholarly journals Global Role for ClpP-Containing Proteases in Stationary-Phase Adaptation of Escherichia coli

2003 ◽  
Vol 185 (1) ◽  
pp. 115-125 ◽  
Author(s):  
Dieter Weichart ◽  
Nadine Querfurth ◽  
Mathias Dreger ◽  
Regine Hengge-Aronis
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Growth Phase ◽  
Proteome Analysis ◽  
Resting Cells ◽  
Wild Type ◽  
Late Stationary Phase ◽  
E Coli ◽  
In The Wild ◽  
Dps Protein

ABSTRACT To elucidate the involvement of proteolysis in the regulation of stationary-phase adaptation, the clpA, clpX, and clpP protease mutants of Escherichia coli were subjected to proteome analysis during growth and during carbon starvation. For most of the growth-phase-regulated proteins detected on our gels, the clpA, clpX, or clpP mutant failed to mount the growth-phase regulation found in the wild type. For example, in the clpP and clpA mutant cultures, the Dps protein, the WrbA protein, and the periplasmic lysine-arginine-ornithine binding protein ArgT did not display the induction typical for late-stationary-phase wild-type cells. On the other hand, in the protease mutants, a number of proteins accumulated to a higher degree than in the wild type, especially in late stationary phase. The proteins affected in this manner include the LeuA, TrxB, GdhA, GlnA, and MetK proteins and alkyl hydroperoxide reductase (AhpC). These proteins may be directly degraded by ClpAP or ClpXP, respectively, or their expression could be modulated by a protease-dependent mechanism. From our data we conclude that the levels of most major growth-phase-regulated proteins in E. coli are at some point controlled by the activity of at least one of the ClpP, ClpA, and ClpX proteins. Cultures of the strains lacking functional ClpP or ClpX also displayed a more rapid loss of viability during extended stationary phase than the wild type. Therefore, regulation by proteolysis seems to be more important, especially in resting cells, than previously suspected.

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