Studies on Bacterial ChemotaxisIII. Effect of Methyl Esters on the Chemotactic Response of Escherichia coli1

1979 ◽  
Keyword(s):  
Escherichia Coli ◽  
Methyl Esters ◽  
Bacterial Chemotaxis ◽  
Chemotactic Response

scholarly journals Free calcium transients in chemotactic and non-chemotactic strains of Escherichia coli determined by using recombinant aequorin

1995 ◽  
Vol 306 (3) ◽  
pp. 865-869 ◽  
Author(s):  
N J Watkins ◽  
M R Knight ◽  
A J Trewavas ◽  
A K Campbell
Keyword(s):  
Escherichia Coli ◽  
Bacterial Chemotaxis ◽  
Chemotactic Response ◽  
Calcium Transients ◽  
Free Calcium ◽  
E Coli ◽  
Proposed Model ◽  
Strain Bl21 ◽  
Recombinant Aequorin ◽  
Strain Ab1157

Intracellular Ca2+ has been previously implicated in the chemotactic response of Escherichia coli. However, no correlative measurements of intracellular free Ca2+ have been made during bacterial chemotaxis, essential if this is to be established. In order to monitor internal free Ca2+ in E. coli during challenge with chemotactic agents, the Ca(2+)-activated photoprotein aequorin was expressed in a chemotactic strain (AB1157) and a non-chemotactic strain [BL21(DE3)] of E. coli. Repellents were found to cause an increase (50-150 nM) in intracellular free Ca2+, whereas attractants caused a small but consistent decrease in intracellular free Ca2+. These data are in agreement with the proposed model that an increase in intracellular free Ca2+ causes tumbling. The effect of increasing external Ca2+ on the regulation of intracellular free Ca2+ in both strains was monitored by using aequorin. The resting level of free Ca2+ in E. coli (AB1157) was found to be 100 nM, which agrees with previous data [Gangola and Rosen (1987) J. Biol. Chem. 262, 12570-12574]. As these results also show differences in the regulation of intracellular free Ca2+ between the two strains in the presence of high external Ca2+ concentrations, this may have implications for the effect of high-Ca2+ environments on E. coli.

Bacterial chemotaxis differences inEscherichia coliisolated from different hosts

2008 ◽  
Vol 54 (12) ◽  
pp. 1043-1052 ◽  
Author(s):  
Sijana H. Dzinic ◽  
Marcella Luercio ◽  
Jeffrey L. Ram
Keyword(s):  
Escherichia Coli ◽  
Carbon Sources ◽  
Bacterial Chemotaxis ◽  
Growth Curves ◽  
Chemotactic Response ◽  
Low Density ◽  
Chemotaxis Assay ◽  
E Coli ◽  
Growth Differences ◽  
Chemotactic Behavior

The mechanisms mediating the association between Escherichia coli and specific hosts are unknown. This study investigates the hypothesis that the host-specific associations of E. coli strains are mediated in part by differences in chemotaxis. To test this hypothesis, chemotactic responses of E. coli strains isolated from different host groups (carnivores, herbivores, and omnivores) were tested with various attractants. In low-density agar chemotaxis assays, the average motility of E. coli in response to aspartate, serine, and ribose among the different groups was not significantly different; however, strains from carnivores responded significantly more to aspartate, relative to their responses to serine, in comparison with strains from herbivores, which responded equally or better to serine than to aspartate. The relatively greater chemotactic response of strains from carnivores to aspartate than to serine was confirmed in a subset of strains by capillary chemotaxis assay. Differences in responses to serine and aspartate were not due to growth differences, as determined by comparison of 24 h growth curves with glycerol, aspartate, and serine carbon sources. The differences in chemotactic behavior of E. coli strains isolated from herbivores and carnivores support the hypothesis that host-specific associations of E. coli strains are mediated in part by differences in chemotactic behavior.

scholarly journals Probing chemotaxis activity inEscherichia coliusing fluorescent protein fusions

2018 ◽  
Author(s):  
Clémence Roggo ◽  
Jan Roelof van der Meer
Keyword(s):  
Escherichia Coli ◽  
Protein Interactions ◽  
Fluorescent Protein ◽  
Fluorescent Proteins ◽  
Bacterial Chemotaxis ◽  
Ph Sensitive ◽  
Flagellar Motors ◽  
Receptor Interactions ◽  
Split Egfp ◽  
Green Fluorescent

ABSTRACTChemotaxis is based on ligand-receptor interactions that are transmitted via protein-protein interactions to the flagellar motors. Ligand-receptor interactions in chemotaxis can be deployed for the development of rapid biosensor assays, but there is no consensus as to what the best readout of such assays would have to be. Here we explore two potential fluorescent readouts of chemotactically activeEscherichia colicells. In the first, we probed interactions between the chemotaxis signaling proteins CheY and CheZ by fusing them individually with non-fluorescent parts of a ‘split’-Green Fluorescent Protein. Wild-type chemotactic cells but not mutants lacking the CheA kinase produced distinguishable fluorescence foci, two-thirds of which localize at the cell poles with the chemoreceptors and one-third at motor complexes. Cells expressing fusion proteins only were attracted to serine sources, demonstrating measurable functional interactions between CheY~P and CheZ. Fluorescent foci based on stable split-eGFP displayed small fluctuations in cells exposed to attractant or repellent, but those based on an unstable ASV-tagged eGFP showed a higher dynamic behaviour both in the foci intensity changes and the number of foci per cell. For the second readout, we expressed the pH-sensitive fluorophore pHluorin in the cyto- and periplasm of chemotactically activeE. coli. Calibrations of pHluorin fluorescence as a function of pH demonstrated that cells accumulating near a chemo-attractant temporally increase cytoplasmic pH while decreasing periplasmic pH. Both readouts thus show promise as proxies for chemotaxis activity, but will have to be further optimized in order to deliver practical biosensor assays.IMPORTANCEBacterial chemotaxis may be deployed for future biosensing purposes with the advantages of its chemoreceptor ligand-specificity and its minute-scale response time. On the downside, chemotaxis is ephemeral and more difficult to quantitatively read out than, e.g., reporter gene expression. It is thus important to investigate different alternative ways to interrogate chemotactic response of cells. Here we gauge the possibilities to measure dynamic response in theEscherichia colichemotaxis pathway resulting from phosphorylated CheY-CheZ interactions by using (unstable) split-fluorescent proteins. We further test whether pH differences between cyto- and periplasm as a result of chemotactic activity can be measured with help of pH-sensitive fluorescent proteins. Our results show that both approaches conceptually function, but will need further improvement in terms of detection and assay types to be practical for biosensing.

scholarly journals Biphasic chemotaxis ofEscherichia colito the microbiota metabolite indole

2020 ◽  
Vol 117 (11) ◽  
pp. 6114-6120 ◽  
Author(s):  
Jingyun Yang ◽  
Ravi Chawla ◽  
Kathy Y. Rhee ◽  
Rachit Gupta ◽  
Michael D. Manson ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Microbial Communities ◽  
Bacterial Chemotaxis ◽  
Dynamic Responses ◽  
Time Dependent ◽  
Flagellar Motor ◽  
Wild Type ◽  
Gi Tract ◽  
Flagellar Motors

Bacterial chemotaxis to prominent microbiota metabolites such as indole is important in the formation of microbial communities in the gastrointestinal (GI) tract. However, the basis of chemotaxis to indole is poorly understood. Here, we exposedEscherichia colito a range of indole concentrations and measured the dynamic responses of individual flagellar motors to determine the chemotaxis response. Below 1 mM indole, a repellent-only response was observed. At 1 mM indole and higher, a time-dependent inversion from a repellent to an attractant response was observed. The repellent and attractant responses were mediated by the Tsr and Tar chemoreceptors, respectively. Also, the flagellar motor itself mediated a repellent response independent of the receptors. Chemotaxis assays revealed that receptor-mediated adaptation to indole caused a bipartite response—wild-type cells were attracted to regions of high indole concentration if they had previously adapted to indole but were otherwise repelled. We propose that indole spatially segregates cells based on their state of adaptation to repel invaders while recruiting beneficial resident bacteria to growing microbial communities within the GI tract.

scholarly journals Cellular Stoichiometry of Chemotaxis Proteins in Sinorhizobium meliloti

2020 ◽  
Vol 202 (14) ◽  
Author(s):  
Timofey D. Arapov ◽  
Rafael Castañeda Saldaña ◽  
Amanda L. Sebastian ◽  
W. Keith Ray ◽  
Richard F. Helm ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Bacillus Subtilis ◽  
Sinorhizobium Meliloti ◽  
Response Regulator ◽  
Bacterial Chemotaxis ◽  
Adaptor Proteins ◽  
Molar Ratio ◽  
Content Type ◽  
Chemotaxis Proteins ◽  
Chemotaxis System

ABSTRACT Chemotaxis systems enable microbes to sense their immediate environment, moving toward beneficial stimuli and away from those that are harmful. In an effort to better understand the chemotaxis system of Sinorhizobium meliloti, a symbiont of the legume alfalfa, the cellular stoichiometries of all ten chemotaxis proteins in S. meliloti were determined. A combination of quantitative immunoblot and mass spectrometry revealed that the protein stoichiometries in S. meliloti varied greatly from those in Escherichia coli and Bacillus subtilis. To compare protein ratios to other systems, values were normalized to the central kinase CheA. All S. meliloti chemotaxis proteins exhibited increased ratios to various degrees. The 10-fold higher molar ratio of adaptor proteins CheW1 and CheW2 to CheA might result in the formation of rings in the chemotaxis array that consist of only CheW instead of CheA and CheW in a 1:1 ratio. We hypothesize that the higher ratio of CheA to the main response regulator CheY2 is a consequence of the speed-variable motor in S. meliloti, instead of a switch-type motor. Similarly, proteins involved in signal termination are far more abundant in S. meliloti, which utilizes a phosphate sink mechanism based on CheA retrophosphorylation to inactivate the motor response regulator versus CheZ-catalyzed dephosphorylation as in E. coli and B. subtilis. Finally, the abundance of CheB and CheR, which regulate chemoreceptor methylation, was increased compared to CheA, indicative of variations in the adaptation system of S. meliloti. Collectively, these results mark significant differences in the composition of bacterial chemotaxis systems. IMPORTANCE The symbiotic soil bacterium Sinorhizobium meliloti contributes greatly to host-plant growth by fixing atmospheric nitrogen. The provision of nitrogen as ammonium by S. meliloti leads to increased biomass production of its legume host alfalfa and diminishes the use of environmentally harmful chemical fertilizers. To better understand the role of chemotaxis in host-microbe interaction, a comprehensive catalogue of the bacterial chemotaxis system is vital, including its composition, function, and regulation. The stoichiometry of chemotaxis proteins in S. meliloti has very few similarities to the systems in Escherichia coli and Bacillus subtilis. In addition, total amounts of proteins are significantly lower. S. meliloti exhibits a chemotaxis system distinct from known models by incorporating new proteins as exemplified by the phosphate sink mechanism.

scholarly journals CheX in the Three-Phosphatase System of Bacterial Chemotaxis

2007 ◽  
Vol 189 (19) ◽  
pp. 7007-7013 ◽  
Author(s):  
Travis J. Muff ◽  
Richard M. Foster ◽  
Peter J. Y. Liu ◽  
George W. Ordal
Keyword(s):  
Escherichia Coli ◽  
Signal Transduction ◽  
Bacillus Subtilis ◽  
Mutant Strain ◽  
Response Regulator ◽  
Bacterial Chemotaxis ◽  
Signal Transduction System ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Phosphatase System

ABSTRACT Bacterial chemotaxis involves the regulation of motility by a modified two-component signal transduction system. In Escherichia coli, CheZ is the phosphatase of the response regulator CheY but many other bacteria, including Bacillus subtilis, use members of the CheC-FliY-CheX family for this purpose. While Bacillus subtilis has only CheC and FliY, many systems also have CheX. The effect of this three-phosphatase system on chemotaxis has not been studied previously. CheX was shown to be a stronger CheY-P phosphatase than either CheC or FliY. In Bacillus subtilis, a cheC mutant strain was nearly complemented by heterologous cheX expression. CheX was shown to overcome the ΔcheC adaptational defect but also generally lowered the counterclockwise flagellar rotational bias. The effect on rotational bias suggests that CheX reduced the overall levels of CheY-P in the cell and did not truly replicate the adaptational effects of CheC. Thus, CheX is not functionally redundant to CheC and, as outlined in the discussion, may be more analogous to CheZ.

scholarly journals Optimal Noise Filtering in the Chemotactic Response of Escherichia coli

2006 ◽  
Vol 2 (11) ◽  
pp. e154 ◽  
Author(s):  
Burton W. Andrews ◽  
Tau-Mu Yi ◽  
Pablo A. Iglesias
Keyword(s):  
Escherichia Coli ◽  
Chemotactic Response ◽  
Noise Filtering

scholarly journals Antimicrobial activity of isolated compounds and semisynthetic derivatives from Miconia ferruginata

2020 ◽  
Vol 4 (1) ◽  
pp. 49
Author(s):  
Gracielle Oliveira Sabbag Cunha ◽  
Ana Paula Terezan ◽  
Andreia Pereira Matos ◽  
Marcela Carmen De Melo Burger ◽  
Paulo Cezar Vieira ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Antimicrobial Activity ◽  
Methyl Esters ◽  
Carboxyl Group ◽  
Isomeric Mixture ◽  
E Coli ◽  
Bacillus Subtilis Atcc ◽  
Derivatives Of

This study evaluated the antimicrobial activity of isolated compounds and semisynthetic derivatives from Miconia ferruginata (Melastomataceae) against five microorganisms: Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Bacillus subtilis (ATCC 6623), Pseudomonas aeruginosa (ATCC 15442), and Candida albicans (ATCC 10231). The isomeric mixture of ursolic and oleanolic acids was active against S. aureus (MIC = 250 μg mL-1) and against E. coli, B. subtilis, and P. aeruginosa (MIC = 500 μg mL-1). The flavone 5,6,7-trihydroxy-4’-methoxyflavone and the methyl esters, semisynthetic derivatives of a mixture of ursolic and oleanolic acids, showed no activity against the tested microorganisms. These results suggest that the carboxyl group present in the triterpenes may contribute to antimicrobial activity.

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