scholarly journals The kinetics of chromosome transfer in Escherichia coli: a mathematical treatment

1962 ◽  
Vol 3 (2) ◽  
pp. 273-281 ◽  
Author(s):  
N. Symonds
Keyword(s):  
Escherichia Coli ◽  
Minimal Medium ◽  
Growth Conditions ◽  
Mathematical Treatment ◽  
Female Cell ◽  
Transfer Delay ◽  
Maximum Delay ◽  
Effective Contact ◽  
Kinetics Of ◽  
Good Agreement

A mathematical treatment has been presented of the ideas of de Haan & Gross concerning transfer delay and chromosomal withdrawal during conjugation In Escherichia coli. The calculations involve three parameters: (i) the maximum delay, λ, which can occur between the formation of effective contact in mating pairs and the initiation of chromosomal transfer, (ii) the probability, b, that mating pairs separate with the withdrawal of that segment of the Hfr chromosome which has entered the female cell, and (iii) the probability, c, that mating pairs separate with the breakage of the Hfr chromosome at the point where it enters the female cell, leaving the injected fragment in the female.A comparison of the theory with the experimental results of de Haan & Gross obtained when chromosomal transfer occurs either in minimal medium or in broth shows good agreement under the following conditions:(i) the value of λ is the same under both growth conditions,(ii) the value of b is the same under both growth conditions,(iii) the value of c is much greater during transfer in broth than it is in minimal medium.

scholarly journals Genome-Wide Analysis of Lipoprotein Expression in Escherichia coli MG1655

2004 ◽  
Vol 186 (10) ◽  
pp. 3254-3258 ◽  
Author(s):  
Stephen J. Brokx ◽  
Michael Ellison ◽  
Troy Locke ◽  
Drell Bottorff ◽  
Laura Frost ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Envelope ◽  
Global Gene Expression ◽  
Growth Conditions ◽  
Rt Pcr ◽  
E Coli ◽  
Genome Wide ◽  
Aerobic And Anaerobic ◽  
Insight Into ◽  
Good Agreement

ABSTRACT To gain insight into the cell envelope of Escherichia coli grown under aerobic and anaerobic conditions, lipoproteins were examined by using functional genomics. The mRNA expression levels of each of these genes under three growth conditions—aerobic, anaerobic, and anaerobic with nitrate—were examined by using both Affymetrix GeneChip E. coli antisense genome arrays and real-time PCR (RT-PCR). Many genes showed significant changes in expression level. The RT-PCR results were in very good agreement with the microarray data. The results of this study represent the first insights into the possible roles of unknown lipoprotein genes and broaden our understanding of the composition of the cell envelope under different environmental conditions. Additionally, these data serve as a test set for the refinement of high-throughput bioinformatic and global gene expression methods.

Variability of Steady-State Bacterial Fluorescence with Respect to Growth Conditions

1993 ◽  
Vol 47 (4) ◽  
pp. 436-440 ◽  
Author(s):  
Burt V. Bronk ◽  
Lou Reinisch
Keyword(s):  
Escherichia Coli ◽  
Emission Spectrum ◽  
Minimal Medium ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Growth Conditions ◽  
Bacterial Spores ◽  
Fluorescence Emission Spectra ◽  
Identification Of Species ◽  
Growth Change

The UV-excited (∼280 nm) fluorescence emission spectra from suspensions of several different species of bacteria are examined to determine to what extent differences in condition of growth change their spectra. This is an important factor if these spectra are considered for use for identification of species. It was found that the spectra were relatively invariant with respect to whether the bacteria were harvested during growth (log phase) or after the medium was depleted (stationary phase). For a given strain of Escherichia coli it was found that the emission spectrum did not change for growth in rich, compared to minimal, medium; however, there was some change for other species. For bacterial spores, the emission spectra were found to be similar for several species. An estimate was made for the quantum yield for Bacillus megaterium spores. The emission spectrum from spores and bacteria was found to change substantially on drying.

scholarly journals The Frequency of Persisters in Escherichia coli Reflects the Kinetics of Awakening from Dormancy

2010 ◽  
Vol 192 (13) ◽  
pp. 3379-3384 ◽  
Author(s):  
Arvi Jõers ◽  
Niilo Kaldalu ◽  
Tanel Tenson
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Bacterial Population ◽  
Growth Conditions ◽  
Stationary Phase Culture ◽  
Phase Culture ◽  
Minor Part ◽  
A Minor ◽  
Kinetics Of ◽  
Fresh Growth Medium

ABSTRACT A genetically homogenous bacterial population may contain physiologically distinct subpopulations. In one such case, a minor part of an otherwise antibiotic-sensitive bacterial population maintains a nondividing state even in a growth-supporting environment and is therefore not killed by bactericidal antibiotics. This phenomenon, called persistence, can lead to failure of antibiotic treatment. We followed the development of sensitivity to killing by ampicillin and norfloxacin when Escherichia coli cells were transferred from a stationary-phase culture into fresh growth medium. In parallel, we monitored growth resumption by individual bacteria. We found that bacteria in a population resumed growth and became sensitive to antibiotics at different times after transfer to fresh medium. Moreover, both growing and dormant bacteria coexisted in the same culture for many hours. The kinetics of awakening was strongly influenced by growth conditions: inocula taken from the same stationary-phase culture led to very different persister frequencies when they were transferred into different fresh media. Bactericidal antibiotics kill cells that have woken up, but the later-awakening subpopulation is tolerant to them and can be identified as persisters when the antibiotic is removed. Our observations demonstrate that persister count is a dynamic measure and that the persister frequency of a particular culture is not a fixed value.

Virus Removal by Filtration

1982 ◽  
Vol 14 (4-5) ◽  
pp. 253-256
Author(s):  
N Sriramula ◽  
M Chaudhuri
Keyword(s):  
Experimental Data ◽  
Escherichia Coli ◽  
Cationic Polyelectrolyte ◽  
Electrokinetic Phenomena ◽  
Virus Removal ◽  
Bacterial Virus ◽  
Gravity Settling ◽  
And Diffusion ◽  
Model Virus ◽  
Good Agreement

An investigation was undertaken on the removal of a model virus, bacterial virus MS2 against Escherichia coli, by sand filtration using untreated, and alum or cationic polyelectrolyte treated media, and uncoagulated as well as alum coagulated influent. Data on discrete virus removal were satisfactorily accounted for by electrokinetic phenomena and diffusion. For virus in association with turbidity, filter coefficients computed from experimental data were in good agreement with those predicted by mechanical straining and gravity settling which were the dominant mechanisms for removal of the turbidity particles to which the viruses attached.

Diffusion model for deposition of epitaxial GaAs layers prepared by the MOCVD method

1991 ◽  
Vol 56 (10) ◽  
pp. 2020-2029
Author(s):  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma ◽  
Rudolf Hladina
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Kinetic Model ◽  
Gas Phase ◽  
Substrate Surface ◽  
Deposition Process ◽  
Hydrogen Atmosphere ◽  
Epitaxial Gaas ◽  
Kinetics Of ◽  
Good Agreement

The authors proposed and treated quantitatively a kinetic model for deposition of epitaxial GaAs layers prepared by reaction of trimethylgallium with arsine in hydrogen atmosphere. The transport of gallium to the surface of the substrate is considered as the controlling process. The influence of the rate of chemical reactions in the gas phase and on the substrate surface on the kinetics of the deposition process is neglected. The calculated dependence of the growth rate of the layers on the conditions of the deposition is in a good agreement with experimental data in the temperature range from 600 to 800°C.

scholarly journals The Lipid Lysyl-Phosphatidylglycerol Is Present in Membranes of Rhizobium tropici CIAT899 and Confers Increased Resistance to Polymyxin B Under Acidic Growth Conditions

2007 ◽  
Vol 20 (11) ◽  
pp. 1421-1430 ◽  
Author(s):  
Christian Sohlenkamp ◽  
Kanaan A. Galindo-Lagunas ◽  
Ziqiang Guan ◽  
Pablo Vinuesa ◽  
Sally Robinson ◽  
...  
Keyword(s):  
Sinorhizobium Meliloti ◽  
Minimal Medium ◽  
Polymyxin B ◽  
Growth Conditions ◽  
Membrane Lipid ◽  
Low Ph ◽  
Wild Type ◽  
Rhizobium Tropici ◽  
Gram Negative ◽  
Inducible Genes

Lysyl-phosphatidylglycerol (LPG) is a well-known membrane lipid in several gram-positive bacteria but is almost unheard of in gram-negative bacteria. In Staphylococcus aureus, the gene product of mprF is responsible for LPG formation. Low pH-inducible genes, termed lpiA, have been identified in the gram-negative α-proteobacteria Rhizobium tropici and Sinorhizobium medicae in screens for acid-sensitive mutants and they encode homologs of MprF. An analysis of the sequenced bacterial genomes reveals that genes coding for homologs of MprF from S. aureus are present in several classes of organisms throughout the bacterial kingdom. In this study, we show that the expression of lpiA from R. tropici in the heterologous hosts Escherichia coli and Sinorhizobium meliloti causes formation of LPG. A wild-type strain of R. tropici forms LPG (about 1% of the total lipids) when the cells are grown in minimal medium at pH 4.5 but not when grown in minimal medium at neutral pH or in complex tryptone yeast (TY) medium at either pH. LPG biosynthesis does not occur when lpiA is deleted and is restored upon complementation of lpiA-deficient mutants with a functional copy of the lpiA gene. When grown in the low-pH medium, lpiA-deficient rhizobial mutants are over four times more susceptible to the cationic peptide polymyxin B than the wild type.

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