Mixed culture kinetics of stringent and relaxed Escherichia coli
 cells in glucose-limited chemostat

Five esters of luciferin were synthesized and compared with native luciferin as substrates for firefly luciferase expressed in live intact mammalian cells. The esters themselves were not substrates for purified luciferase, but four were substrates for a purified esterase and all appeared to be hydrolysed to luciferin within mammalian cells. At a substrate concentration of 0.01 mM, the peak luminescence from the cos cells expressing luciferase was up to 6-fold greater with the esters than with unmodified luciferin. At 0.1 mM, the difference between luciferin and the esters was decreased. The kinetics of the luminescent signal with the different luciferin esters varied significantly, indicating possible differences in the rates of uptake, breakdown and enzyme inhibition. The esters did not support luminescence from Escherichia coli cells expressing firefly luciferase, suggesting a lack of appropriate esterase activity in this particular strain. The esters could be useful for the assay of luciferase expression in intact mammalian cells when luciferin levels are limiting, for example in tissues, and in plants. Alternative luciferin derivatives may allow further improvements in sensitivity.

Download Full-text

Kinetics of mercuric reduction in intact and permeabilized Escherichia coli cells

Enzyme and Microbial Technology ◽

10.1016/0141-0229(90)90022-i ◽

1990 ◽

Vol 12 (11) ◽

pp. 854-859 ◽

Cited By ~ 8

Author(s):

George P. Philippidis ◽

Janet L. Schottel ◽

Wei-Shou Hu

Keyword(s):

Escherichia Coli ◽

Escherichia Coli Cells ◽

Kinetics Of

Download Full-text

Antagonism of the B subunit of DNA gyrase eliminates plasmids pBR322 and pMG110 from Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.152.1.338-344.1982 ◽

1982 ◽

Vol 152 (1) ◽

pp. 338-344

Author(s):

J S Wolfson ◽

D C Hooper ◽

M N Swartz ◽

G L McHugh

Keyword(s):

Escherichia Coli ◽

Dna Gyrase ◽

B Subunit ◽

Plasmid Loss ◽

Escherichia Coli Cells ◽

Bacterial Mutant ◽

Bacterial Enzyme ◽

Kinetics Of ◽

Plasmid Elimination ◽

Native Plasmid

The constructed plasmid pBR322 and the native plasmid pMG110 were eliminated (cured) from growing Escherichia coli cells by the antagonism of the B subunit of the bacterial enzyme DNA gyrase. The antagonism may be by the growth of cells (i) at semipermissive temperatures in a bacterial mutant containing a thermolabile gyrase B subunit or (ii) at semipermissive concentrations of coumermycin A1, an antibiotic that specifically inhibits the B subunit of DNA gyrase. The kinetics of plasmid elimination indicate that plasmid loss occurs too rapidly to be explained solely by the faster growth of that plasmid-free bacteria and, therefore, represents interference with plasmid maintenance.

Download Full-text

Colicins, spermine and cephalosporins: a competitive interaction with the OmpF eyelet

Biochemical Journal ◽

10.1042/bj20030814 ◽

2003 ◽

Vol 376 (1) ◽

pp. 245-252 ◽

Cited By ~ 18

Author(s):

Jérôme BREDIN ◽

Valérie SIMONET ◽

Ramkumar IYER ◽

Anne H. DELCOUR ◽

Jean-Marie PAGÈS

Keyword(s):

Escherichia Coli ◽

Structure Function ◽

Essential Role ◽

Wild Type ◽

Potassium Efflux ◽

Channel Size ◽

Escherichia Coli Cells ◽

Epitope Structure ◽

Resistant Strains ◽

Kinetics Of

The L3 loop is an important feature of the OmpF porin structure, contributing to both channel size and electrostatic properties. Colicins A and N, spermine, and antibiotics that use OmpF to penetrate the cell, were used to investigate the structure–function relationships of L3. Spermine was found to protect efficiently cells expressing wild-type OmpF from colicin action. Among other solutes, sugars had minor effects on colicin A activity, whereas competitions between colicin A and antibiotic fluxes were observed. Among the antibiotics tested, cefepime appeared the most efficient. Escherichia coli cells expressing various OmpF proteins mutated in the eyelet were tested for their susceptibility to colicin A, and resistant strains were found only among L3 mutants. Mutations at residues 119 and 120 were the most effective at conferring resistance to colicin A, probably due to epitope structure alteration, as revealed by a specific antipeptide. More detailed information was obtained on mutants D113A and D121A, by focusing on the kinetics of colicin A and colicin N activities through measurements of potassium efflux. D113 appeared to play an essential role for colicin A activity, whereas colicin N activity was more dependent on D121 than on D113.

Download Full-text

Bacteriophage λ proliferation in Escherichia coli under the influence of microwave irradiation

Archives of Biological Sciences ◽

10.2298/abs1004935m ◽

2010 ◽

Vol 62 (4) ◽

pp. 935-940

Author(s):

Natasa Milojevic ◽

D. Stanisavljev ◽

Biljana Nikolic ◽

M. Beljanski ◽

Ljiljana Kolar-Anic ◽

...

Keyword(s):

Escherichia Coli ◽

Thermal Effects ◽

Absorption Rate ◽

Microwave Treatment ◽

Model System ◽

Bacterial Metabolism ◽

Bacteriophage Λ ◽

Optimal Temperature ◽

Escherichia Coli Cells ◽

Kinetics Of

The influence of microwaves on bacterial metabolism was investigated using the proliferation of bacteriophage ? in Escherichia coli cells as a model system. All experiments were performed under the same microwave absorption rate and constant temperature. Microwave treatment had no effect on bacterial or phage viability, or on phage adsorption. Microwaves significantly influenced phage proliferation but the effects depended on the experimental temperature. The kinetics of phage proliferation decreased with irradiation at the optimal temperature and increased at the suboptimal temperature. This result could be ascribed to the specific thermal effects of microwaves.

Download Full-text