scholarly journals Blue light is a universal tactic signal forEscherichia coli

2017 ◽  
Author(s):  
Tatyana Perlova ◽  
Martin Gruebele ◽  
Yann R. Chemla
Keyword(s):  
Blue Light ◽  
Light Exposure ◽  
Biological Significance ◽  
Proton Motive Force ◽  
Motive Force ◽  
Swimming Velocity ◽  
Bacterial Strains ◽  
E Coli ◽  
Before And After ◽  
Swimming Bacteria

AbstractBlue light has been shown to elicit a tumbling response inE. coli, a non-phototrophic bacterium. The exact mechanism of this phototactic response is still unknown, and its biological significance remains unclear. Here, we quantify phototaxis inE. coliby analyzing single-cell trajectories in populations of free-swimming bacteria before and after light exposure. Bacterial strains expressing only one type of chemoreceptor reveal that all fiveE. colireceptors - Aer, Tar, Tsr, Tap and Trg - are capable of mediating a response to light. In particular, light exposure elicits a running response in Tap-only strain, the opposite of the tumbling response observed for all other strains. Light therefore emerges as a universal stimulus for allE. colichemoreceptors. We also show that blue light exposure causes a reversible decrease in swimming velocity, a proxy for proton motive force. We hypothesize that rather than sensing light directly, chemoreceptors sense light-induced perturbations in proton motive force.ImportanceOur findings provide new insights on the mechanism ofE. coliphototaxis, showing that all five chemoreceptor types respond to light and that their interactions play an important role in cell behavior. Our results also open up new avenues for examining and manipulatingE. colitaxis. Since light is a universal stimulus, it may provide a way to quantify interactions between different types of receptors. Since light is easier to control spatially and temporally than chemicals, it may be used to study swimming behavior in complex environments. Since phototaxis can cause migration ofE. colibacteria in light gradients, light may be used to control bacterial density for studying density-dependent processes in bacteria.

scholarly journals Blue Light Is a Universal Signal forEscherichia coliChemoreceptors

2019 ◽  
Vol 201 (11) ◽  
Author(s):  
Tatyana Perlova ◽  
Martin Gruebele ◽  
Yann R. Chemla
Keyword(s):  
Blue Light ◽  
Light Exposure ◽  
Proton Motive Force ◽  
Motive Force ◽  
Swimming Velocity ◽  
Bacterial Strains ◽  
Content Type ◽  
E Coli ◽  
Before And After ◽  
Swimming Bacteria

ABSTRACTBlue light has been shown to elicit a tumbling response inEscherichia coli, a nonphototrophic bacterium. The exact mechanism of this phototactic response is still unknown. Here, we quantify phototaxis inE. coliby analyzing single-cell trajectories in populations of free-swimming bacteria before and after light exposure. Bacterial strains expressing only one type of chemoreceptor reveal that all fiveE. colireceptors (Aer, Tar, Tsr, Tap, and Trg) are capable of mediating responses to light. In particular, light exposure elicits a running response in the Tap-only strain, the opposite of the tumbling responses observed for all other strains. Therefore, light emerges as a universal stimulus for allE. colichemoreceptors. We also show that blue light exposure causes a reversible decrease in swimming velocity, a proxy for proton motive force. This result is consistent with a previously proposed hypothesis that, rather than sensing light directly, chemoreceptors sense light-induced perturbations in proton motive force, although other factors are also likely to contribute.IMPORTANCEOur findings provide new insights into the mechanism ofE. coliphototaxis, showing that all five chemoreceptor types respond to light and their interactions play an important role in cell behavior. Our results also open up new avenues for examining and manipulatingE. colitaxis. Since light is a universal stimulus, it may provide a way to quantify interactions among different types of receptors. Because light is easier to control spatially and temporally than chemicals, it may be used to study swimming behavior in complex environments. Since phototaxis can cause migration ofE. colibacteria in light gradients, light may be used to control bacterial density for studying density-dependent processes in bacteria.

scholarly journals Mechanism of Bactericidal Activity of Microcin L inEscherichia coliandSalmonella enterica

2010 ◽  
Vol 55 (3) ◽  
pp. 997-1007 ◽  
Author(s):  
Natacha Morin ◽  
Isabelle Lanneluc ◽  
Nathalie Connil ◽  
Marie Cottenceau ◽  
Anne Marie Pons ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Bactericidal Activity ◽  
Salmonella Enterica ◽  
Cytoplasmic Membrane ◽  
Genetic System ◽  
Proton Motive Force ◽  
Motive Force ◽  
Membrane Properties ◽  
Outer Membrane Receptor ◽  
E Coli

ABSTRACTFor the first time, the mechanism of action of microcin L (MccL) was investigated in live bacteria. MccL is a gene-encoded peptide produced byEscherichia coliLR05 that exhibits a strong antibacterial activity against relatedEnterobacteriaceae, includingSalmonella entericaserovars Typhimurium and Enteritidis. We first subcloned the MccL genetic system to remove the sequences not involved in MccL production. We then optimized the MccL purification procedure to obtain large amounts of purified microcin to investigate its antimicrobial and membrane properties. We showed that MccL did not induce outer membrane permeabilization, which indicated that MccL did not use this way to kill the sensitive cell or to enter into it. Using a set ofE. coliandSalmonella entericamutants lacking iron-siderophore receptors, we demonstrated that the MccL uptake required the outer membrane receptor Cir. Moreover, the MccL bactericidal activity was shown to depend on the TonB protein that transduces the proton-motive force of the cytoplasmic membrane to transport iron-siderophore complexes across the outer membrane. Using carbonyl cyanide 3-chlorophenylhydrazone, which is known to fully dissipate the proton-motive force, we proved that the proton-motive force was required for the bactericidal activity of MccL onE. coli. In addition, we showed that a primary target of MccL could be the cytoplasmic membrane: a high level of MccL disrupted the inner membrane potential ofE. colicells. However, no permeabilization of the membrane was detected.

Critical bacterial concentration for the onset of collective swimming

2009 ◽  
Vol 632 ◽  
pp. 359-400 ◽  
Author(s):  
GANESH SUBRAMANIAN ◽  
DONALD L. KOCH
Keyword(s):  
Stability Analysis ◽  
Threshold Concentration ◽  
Swimming Velocity ◽  
Bacterial Number ◽  
Bacterial Concentration ◽  
E Coli ◽  
Weakly Interacting ◽  
Swimming Bacteria ◽  
Dilute Suspension ◽  
The Stability

We examine the stability of a suspension of swimming bacteria in a Newtonian medium. The bacteria execute a run-and-tumble motion, runs being periods when a bacterium on average swims in a given direction; runs are interrupted by tumbles, leading to an abrupt, albeit correlated, change in the swimming direction. An instability is predicted to occur in a suspension of ‘pushers’ (e.g.E. Coli,Bacillus subtilis, etc.), and owes its origin to the intrinsic force dipoles of such bacteria. Unlike the dipole induced in an inextensible fibre subject to an axial straining flow, the forces constituting the dipole of a pusher are directed outward along its axis. As a result, the anisotropy in the orientation distribution of bacteria due to an imposed velocity perturbation drives a disturbance velocity field that acts to reinforce the perturbation. For long wavelengths, the resulting destabilizing bacterial stress is Newtonian but with a negative viscosity. The suspension becomes unstable when the total viscosity becomes negative. In the dilute limit (nL3≪ 1), a linear stability analysis gives the threshold concentration for instability as (nL3)crit= ((30/Cℱ(r))(DrL/U)(1 + 1/(6τDr)))/(1−(15𝒢(r)/Cℱ(r))(DrL/U)(1 + 1/(6τDr))) for perfectly random tumbles; here,LandUare the length and swimming velocity of a bacterium,nis the bacterial number density,Drcharacterizes the rotary diffusion during a run and τ−1is the average tumbling frequency. The function ℱ(r) characterizes the rotation of a bacterium of aspect ratiorin an imposed linear flow; ℱ(r) = (r2−1)/(r2+ 1) for a spheroid, and ℱ(r) ≈ 1 for a slender bacterium (r≫ 1). The function 𝒢(r) characterizes the stabilizing viscous response arising from the resistance of a bacterium to a deforming ambient flow; 𝒢(r) = 5π/6 for a rigid spherical bacterium, and 𝒢(r)≈ π/45(lnr) for a slender bacterium. Finally, the constantCdenotes the dimensionless strength of the bacterial force dipole in units of μU L2; forE. Coli,C≈ 0.57. The threshold concentration diverges in the limit ((15𝒢(r)/Cℱ(r)) (DrL/U)(1 + 1/(6τDr))) → 1. This limit defines a critical swimming speed,Ucrit= (DrL)(15𝒢(r)/Cℱ(r))(1 + 1/(6τDr)). For speeds smaller than this critical value, the destabilizing bacterial stress remains subdominant and a dilute suspension of these swimmers therefore responds to long-wavelength perturbations in a manner similar to a suspension of passive rigid particles, that is, with a net enhancement in viscosity proportional to the bacterial concentration.On the other hand, the stability analysis predicts that the above threshold concentration reduces to zero in the limitDr→ 0, τ → ∞, and a suspension of non-interacting straight swimmers is therefore always unstable. It is then argued that the dominant effect of hydrodynamic interactions in a dilute suspension of such swimmers is via an interaction-driven orientation decorrelation mechanism. The latter arises from uncorrelated pair interactions in the limitnL3≪ 1, and for slender bacteria in particular, it takes the form of a hydrodynamic rotary diffusivity (Dhr); forE. Coli, we findDhr= 9.4 × 10−5(nUL2). From the above expression for the threshold concentration, it may be shown that even a weakly interacting suspension of slender smooth-swimming bacteria (r≫ 1, ℱ(r) ≈ 1, τ → ∞) will be stable providedDhr> (C/30)(nUL2) in the limitnL3≪ 1. The hydrodynamic rotary diffusivity ofE. Coliis, however, too small to stabilize a dilute suspension of these swimmers, and a weakly interacting suspension ofE. Coliremains unstable.

Probing the dynamics of the proton-motive force in E. coli

2014 ◽  
Author(s):  
Tom J. Zajdel ◽  
Michaela A. TerAvest ◽  
Behzad Rad ◽  
Caroline M. Ajo-Franklin ◽  
Michel M. Maharbiz
Keyword(s):  
Proton Motive Force ◽  
Motive Force ◽  
E Coli

scholarly journals Molecular Cloning and Functional Expression inLactobacillus plantarum 80 of xylT, Encoding thed-Xylose–H+ Symporter ofLactobacillus brevis

1998 ◽  
Vol 64 (12) ◽  
pp. 4720-4728 ◽  
Author(s):  
Stéphane Chaillou ◽  
Yeou-Cherng Bor ◽  
Carl A. Batt ◽  
Pieter W. Postma ◽  
Peter H. Pouwels
Keyword(s):  
Xylose Isomerase ◽  
Proton Motive Force ◽  
Motive Force ◽  
Affinity Constant ◽  
Transport Activity ◽  
Gene Encoding ◽  
Kinase Gene ◽  
E Coli ◽  
Xylose Transport ◽  
Xylulose Kinase

ABSTRACT A 3-kb region, located downstream of the Lactobacillus brevis xylA gene (encoding d-xylose isomerase), was cloned in Escherichia coli TG1. The sequence revealed two open reading frames which could code for the d-xylulose kinase gene (xylB) and another gene (xylT) encoding a protein of 457 amino acids with significant similarity to thed-xylose–H+ symporters of E. coli, XylE (57%), and Bacillus megaterium, XylT (58%), to the d-xylose–Na+ symporter ofTetragenococcus halophila, XylE (57%), and to thel-arabinose–H+ symporter of E. coli, AraE (60%). The L. brevis xylABT genes showed an arrangement similar to that of the B. megaterium xylABT operon and the T. halophila xylABE operon. Southern hybridization performed with the Lactobacillus pentosus xylR gene (encoding the d-xylose repressor protein) as a probe revealed the existence of a xylR homologue inL. brevis which is not located with thexyABT locus. The existence of a functional XylR was further suggested by the presence of xylO sequences upstream ofxylA and xylT and by the requirement ofd-xylose for the induction of d-xylose isomerase, d-xylulose kinase, and d-xylose transport activities in L. brevis. When L. brevis was cultivated in a mixture of d-glucose andd-xylose, the d-xylose isomerase andd-xylulose kinase activities were reduced fourfold and thed-xylose transport activity was reduced by sixfold, suggesting catabolite repression by d-glucose ofd-xylose assimilation. The xylT gene was functionally expressed in Lactobacillus plantarum 80, a strain which lacks proton motive force-linked d-xylose transport activity. The role of the XylT protein was confirmed by the accumulation of d-xylose in L. plantarum80 cells, and this accumulation was dependent on the proton motive force generated by either malolactic fermentation or by the metabolism of d-glucose. The apparent affinity constant of XylT ford-xylose was approximately 215 μM, and the maximal initial velocity of transport was 35 nmol/min per mg (dry weight). Furthermore, of a number of sugars tested, only 6-deoxy-d-glucose inhibited the transport ofd-xylose by XylT competitively, with aKi of 220 μM.

scholarly journals Membrane Transporters of the Major Facilitator Superfamily Are Essential for Long-Term Maintenance of Phenotypic Tolerance to Multiple Antibiotics in E. coli

2021 ◽  
Author(s):  
Yingkun Wan ◽  
Miaomiao Wang ◽  
Edward Wai Chi Chan ◽  
Sheng Chen
Keyword(s):  
Proton Motive Force ◽  
Membrane Transporters ◽  
Motive Force ◽  
Major Facilitator Superfamily ◽  
Starvation Stress ◽  
E Coli ◽  
Major Facilitator ◽  
Term Maintenance ◽  
Multiple Antibiotics

We recently showed that the antibiotic-tolerant subpopulation of bacteria or persisters actively maintain the transmembrane proton motive force (PMF) to survive starvation stress for a prolonged period. This work further shows that the reason why antibiotic persisters need to maintain PMF is that PMF is required to support a range of efflux or transportation functions.

scholarly journals Proton motive force underpins respiration-mediated potentiation of aminoglycoside lethality in pathogenic Escherichia coli

2022 ◽  
Vol 204 (1) ◽  
Author(s):  
Calum M. Webster ◽  
Ayrianna M. Woody ◽  
Safura Fusseini ◽  
Louis G. Holmes ◽  
Gary K. Robinson ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Respiratory Chain ◽  
Proton Motive Force ◽  
Motive Force ◽  
Gram Negative Bacteria ◽  
Ros Production ◽  
Gram Negative ◽  
E Coli ◽  
Pathogenic Escherichia Coli ◽  
Aminoglycoside Toxicity

AbstractIt is well known that loss of aerobic respiration in Gram-negative bacteria can diminish the efficacy of a variety of bactericidal antibiotics, which has lead to subsequent demonstrations that the formation of reactive oxygen species (ROS) and the proton motive force (PMF) can both play a role in antibiotic toxicity. The susceptibility of Gram-negative bacteria to aminoglycoside antibiotics, particularly gentamicin, has previously been linked to both the production of ROS and the rate of antibiotic uptake that is mediated by the PMF, although the relative contributions of ROS and PMF to aminoglycoside toxicity has remained poorly understood. Herein, gentamicin was shown to elicit a very modest increase in ROS levels in an aerobically grown Escherichia coli clinical isolate. The well-characterised uncoupler 2,4-dinitrophenol (DNP) was used to disrupt the PMF, which resulted in a significant decrease in gentamicin lethality towards E. coli. DNP did not significantly alter respiratory oxygen consumption, supporting the hypothesis that this uncoupler does not increase ROS production via elevated respiratory oxidase activity. These observations support the hypothesis that maintenance of PMF rather than induction of ROS production underpins the mechanism for how the respiratory chain potentiates the toxicity of aminoglycosides. This was further supported by the demonstration that the uncoupler DNP elicits a dramatic decrease in gentamicin lethality under anaerobic conditions. Together, these data strongly suggest that maintenance of the PMF is the dominant mechanism for the respiratory chain in potentiating the toxic effects of aminoglycosides.

SYNTHESIS, CHARACTERIZATION AND BIOLOGICAL EVALUATION OF 3-FORMYL INDOLE BASED SCHIFF BASES

2018 ◽  
Vol 7 (6) ◽  
Author(s):  
Singh Gurvinder ◽  
Singh Prabhsimran ◽  
Dhawan R. K.
Keyword(s):  
Antimicrobial Activity ◽  
Spectral Analysis ◽  
Schiff Bases ◽  
Antimicrobial Agents ◽  
Biological Evaluation ◽  
Fungal Strain ◽  
Bacterial Strains ◽  
Standard Drug ◽  
Gram Negative ◽  
E Coli

In order to develop new antimicrobial agents, a series of 3-formyl indole based Schiff bases were synthesized by reacting 3-formyl indole(indole-3-carboxaldehyde) with substituted aniline taking ethanol as solvent. The reaction was carried in the presence of small amount of p-toluene sulphonic acid as catalyst.All the synthesized compounds were characterized by IR, 1H-NMR spectral analysis. All the synthesized compounds were evaluated for antimicrobial activity against two gram positive bacterial strains (B. subtilisand S. aureus) and two gram negative bacterial strains (P. aeruginosaand E. coli) and one fungal strain (C. albicans). All the synthesized compounds were found to have moderate to good antimicrobial activity. The  standard drug amoxicillin, fluconazole were used for antimicrobial activity. Among the synthesized compounds, the maximum antimicrobial activity was shown by compounds GS04, GS07, GS08 and GS10.

Nighttime Blue Light Exposure and Breast Cancer

2021 ◽  
pp. 30-33
Author(s):  
David Jaynes ◽  
Paul Switzer
Keyword(s):  
Breast Cancer ◽  
Risk Factor ◽  
Blue Light ◽  
Shift Work ◽  
Light Exposure ◽  
Night Shift ◽  
Background Information ◽  
Common Disease ◽  
Essential Information ◽  
Night Shift Work

The purpose of this article is to provide background information and the current understanding of a less familiar cause of female breast cancer; exposure to ultraviolet light at night. Breast cancer is a common disease that causes significant morbidity and mortality in women. There are several risk factors for breast cancer, most of which are genetic and environmental in nature. An often-overlooked risk factor is exposure to blue light during night shift work, which decreases melatonin production. One of the many cancer-preventing properties of melatonin is to limit estrogen production. Increased lifetime exposure to estrogen is a well-known cause of breast cancer. Awareness of nighttime blue light exposure as a breast cancer risk factor by women doing night shift work and those exposed to nighttime light via smartphones and laptops, is essential information to know so that protective measures can be taken.

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