scholarly journals The role of mechanical forces in the planar-to-bulk transition in growing Escherichia coli microcolonies

2014 ◽  
Vol 11 (97) ◽  
pp. 20140400 ◽  
Author(s):  
Matthew A. A. Grant ◽  
Bartłomiej Wacław ◽  
Rosalind J. Allen ◽  
Pietro Cicuta
Keyword(s):  
Escherichia Coli ◽  
Colony Size ◽  
Three Dimensional ◽  
Phenomenological Theory ◽  
Mechanical Forces ◽  
Bacterial Cells ◽  
Experimental Conditions ◽  
Surrounding Matrix ◽  
Dimensional Growth

Mechanical forces are obviously important in the assembly of three-dimensional multicellular structures, but their detailed role is often unclear. We have used growing microcolonies of the bacterium Escherichia coli to investigate the role of mechanical forces in the transition from two-dimensional growth (on the interface between a hard surface and a soft agarose pad) to three-dimensional growth (invasion of the agarose). We measure the position within the colony where the invasion transition happens, the cell density within the colony and the colony size at the transition as functions of the concentration of the agarose. We use a phenomenological theory, combined with individual-based computer simulations, to show how mechanical forces acting between the bacterial cells, and between the bacteria and the surrounding matrix, lead to the complex phenomena observed in our experiments—in particular the observation that agarose concentration non-trivially affects the colony size at transition. Matching these approaches leads to a prediction for how the friction between the bacteria and the agarose should vary with agarose concentration. Our experimental conditions mimic numerous clinical and environmental scenarios in which bacteria invade soft matrices, as well as shedding more general light on the transition between two- and three-dimensional growth in multicellular assemblies.

Effect of Position and Flow Waveform on the Fluid Mechanics of a Stenosed Human Right Coronary Artery

2001 ◽  
Author(s):  
K. B. Chandran ◽  
S. D. Ramaswamy ◽  
Y.-G. Lai ◽  
A. Wahle ◽  
M. Sonka
Keyword(s):  
Fluid Mechanics ◽  
Three Dimensional ◽  
Coronary Vessels ◽  
Mechanical Forces ◽  
Flow Waveform ◽  
Human Right ◽  
Plaque Growth ◽  
Oscillatory Shear Stress ◽  
The Relationship

Abstract Complete occlusion in any of the coronary vessels leads to a myocardial infarction. The role of fluid mechanical forces in atheroma development has been widely accepted because of preferential plaque growth at certain locations of the vessel geometry, such as a bifurcation or regions of high degrees of curvature. Areas of low and/or oscillatory shear stress have been correlated with atheroma development [1]. In order to determine the relationship between fluid mechanical stresses and development of lesions in the coronary vessels, it is important to analyze the fluid mechanics in actual three-dimensional geometries, incorporating the time-dependent translation and geometric alterations of these vessels [2,3].

scholarly journals Genome-Wide Transcriptional Profiling of the Escherichia coli Response to a Proline-Rich Antimicrobial Peptide

2004 ◽  
Vol 48 (9) ◽  
pp. 3260-3267 ◽  
Author(s):  
Linda Tomasinsig ◽  
Marco Scocchi ◽  
Romina Mettulio ◽  
Margherita Zanetti
Keyword(s):  
Escherichia Coli ◽  
Bacterial Resistance ◽  
Transcriptional Profiling ◽  
Transcriptional Response ◽  
Bacterial Cells ◽  
Experimental Conditions ◽  
Bacterial Membranes ◽  
Transcriptional Alterations ◽  
Proline Rich Peptide ◽  
Bacterial Genes

ABSTRACT Most antimicrobial peptides (AMPs) impair the viability of target bacteria by permeabilizing bacterial membranes. However, the proline-rich AMPs have been shown to kill susceptible organisms without causing significant membrane perturbation and may act by inhibiting the activity of bacterial targets. To gain initial insight into the events that follow interaction of a proline-rich peptide with bacterial cells, we used DNA macroarray technology to monitor transcriptional alterations of Escherichia coli in response to challenge with a subinhibitory concentration of the proline-rich Bac7(1-35). Substantial changes in the expression levels of 70 bacterial genes from various functional categories were detected. Among these, 26 genes showed decreased expression, while 44 genes, including genes that are potentially involved in bacterial resistance to antimicrobials, showed increased expression. The generation of a transcriptional response under the experimental conditions used is consistent with the ability of Bac7(1-35) to interact with bacterial components and affect biological processes in this organism.

Effectiveness and Functional Mechanism of a Multicomponent Sanitizer against Biofilms Formed by Escherichia coli O157:H7 and Five Salmonella Serotypes Prevalent in the Meat Industry

2020 ◽  
Vol 83 (4) ◽  
pp. 568-575
Author(s):  
RONG WANG ◽  
YOU ZHOU ◽  
NORASAK KALCHAYANAND ◽  
DAYNA M. HARHAY ◽  
TOMMY L. WHEELER
Keyword(s):  
Escherichia Coli ◽  
Salmonella Enterica ◽  
Three Dimensional ◽  
Short Exposure ◽  
Escherichia Coli O157 ◽  
Bacterial Cells ◽  
Meat Processing ◽  
E Coli ◽  
Biofilm Removal ◽  
Biofilm Structure

ABSTRACT Biofilm formation by Escherichia coli O157:H7 and Salmonella enterica at meat processing plants poses a potential risk of meat product contamination. Many common sanitizers are unable to completely eradicate biofilms formed by these foodborne pathogens because of the three-dimensional biofilm structure and the presence of bacterial extracellular polymeric substances (EPSs). A novel multifaceted approach combining multiple chemical reagents with various functional mechanisms was used to enhance the effectiveness of biofilm control. We tested a multicomponent sanitizer consisting of a quaternary ammonium compound (QAC), hydrogen peroxide, and the accelerator diacetin for its effectiveness in inactivating and removing Escherichia coli O157:H7 and Salmonella enterica biofilms under meat processing conditions. E. coli O157:H7 and Salmonella biofilms on common contact surfaces were treated with 10, 20, or 100% concentrations of the multicomponent sanitizer solution for 10 min, 1 h, or 6 h, and log reductions in biofilm mass were measured. Scanning electron microscopy (SEM) was used to directly observe the effect of sanitizer treatment on biofilm removal and bacterial morphology. After treatment with the multicomponent sanitizer, viable E. coli O157:H7 and Salmonella biofilm cells were below the limit of detection, and the prevalence of both pathogens was low. After treatment with a QAC-based control sanitizer, surviving bacterial cells were countable, and pathogen prevalence was higher. SEM analysis of water-treated control samples revealed the three-dimensional biofilm structure with a strong EPS matrix connecting bacteria and the contact surface. Treatment with 20% multicomponent sanitizer for 10 min significantly reduced biofilm mass and weakened the EPS connection. The majority of the bacterial cells had altered morphology and compromised membrane integrity. Treatment with 100% multicomponent sanitizer for 10 min dissolved the EPS matrix, and no intact biofilm structure was observed; instead, scattered clusters of bacterial aggregates were detected, indicating the loss of cell viability and biofilm removal. These results indicate that the multicomponent sanitizer is effective, even after short exposure with dilute concentrations, against E. coli O157:H7 and S. enterica biofilms. HIGHLIGHTS

scholarly journals The role of ribonuclease II in the maturation of precursor 16S ribosomal ribonucleic acid in Escherichia coli

1974 ◽  
Vol 140 (3) ◽  
pp. 443-450 ◽  
Author(s):  
John R. Dean ◽  
John Sykes
Keyword(s):  
Escherichia Coli ◽  
Enzyme Activity ◽  
Maximum Activity ◽  
Exponential Phase ◽  
Temperature Sensitive ◽  
Permissive Temperature ◽  
Experimental Conditions ◽  
Inhibition Of Growth ◽  
Ribosomal Ribonucleic Acid

The suggested involvement of ribonuclease II in the maturation of rRNA has been examined directly by determining the activity of the enzyme and the amount of p16S rRNA in cell-free extracts from Escherichia coli A19 and its temperature-sensitive derivative N464 grown under experimental conditions designed to vary the amounts of enzyme and precursor independently. In strain A19 the enzyme showed maximum activity in circumstances where the amount of p16S rRNA was normal (e.g. exponential-phase cells) or raised eight times (e.g. during inhibition of growth by methionine starvation of the relaxed auxotroph or by chloramphenicol or puromycin treatment). In strain N464 at the non-permissive temperature the ribonuclease II activity may be decreased by 50% without effect upon the amount of p16S rRNA, whereas in methionine starvation of this strain the enzyme activity is at a maximum and the p16S rRNA is eight times that in exponential-phase cells. These observations are discussed in relation to the previously implied role of ribonuclease II in the maturation of rRNA within ribosome precursors.

scholarly journals FpvA-Mediated Ferric Pyoverdine Uptake in Pseudomonas aeruginosa: Identification of Aromatic Residues in FpvA Implicated in Ferric Pyoverdine Binding and Transport

2005 ◽  
Vol 187 (24) ◽  
pp. 8511-8515 ◽  
Author(s):  
Jiang-Sheng Shen ◽  
Valérie Geoffroy ◽  
Shadi Neshat ◽  
Zongchao Jia ◽  
Allison Meldrum ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Three Dimensional ◽  
Binding Pocket ◽  
Dimensional Structure ◽  
Aromatic Residues ◽  
Three Dimensional Structure

ABSTRACT A number of aromatic residues were seen to cluster in the upper portion of the three-dimensional structure of the FpvA ferric pyoverdine receptor of Pseudomonas aeruginosa, reminiscent of the aromatic binding pocket for ferrichrome in the FhuA receptor of Escherichia coli. Alanine substitutions in three of these, W362, W391, and F795, markedly compromised ferric pyoverdine binding and transport, consistent with a role of FpvA in ferric pyoverdine recognition.

scholarly journals Functional Analysis of the Carbohydrate-Binding Domains of Erwinia chrysanthemi Cel5 (Endoglucanase Z) and an Escherichia coli Putative Chitinase

1999 ◽  
Vol 181 (15) ◽  
pp. 4611-4616 ◽  
Author(s):  
Helen D. Simpson ◽  
Frederic Barras
Keyword(s):  
Escherichia Coli ◽  
Catalytic Domain ◽  
Three Dimensional ◽  
Site Directed Mutagenesis ◽  
Erwinia Chrysanthemi ◽  
Dimensional Structure ◽  
Carbohydrate Binding ◽  
Binding Domains ◽  
Cellulose Binding

ABSTRACT The Cel5 cellulase (formerly known as endoglucanase Z) fromErwinia chrysanthemi is a multidomain enzyme consisting of a catalytic domain, a linker region, and a cellulose binding domain (CBD). A three-dimensional structure of the CBDCel5 has previously been obtained by nuclear magnetic resonance. In order to define the role of individual residues in cellulose binding, site-directed mutagenesis was performed. The role of three aromatic residues (Trp18, Trp43, and Tyr44) in cellulose binding was demonstrated. The exposed potential hydrogen bond donors, residues Gln22 and Glu27, appeared not to play a role in cellulose binding, whereas residue Asp17 was found to be important for the stability of Cel5. A deletion mutant lacking the residues Asp17 to Pro23 bound only weakly to cellulose. The sequence of CBDCel5 exhibits homology to a series of five repeating domains of a putative large protein, referred to as Yheb, from Escherichia coli. One of the repeating domains (Yheb1), consisting of 67 amino acids, was cloned from the E. coli chromosome and purified by metal chelating chromatography. While CBDCel5 bound to both cellulose and chitin, Yheb1 bound well to chitin, but only very poorly to cellulose. The Yheb protein contains a region that exhibits sequence homology with the catalytic domain of a chitinase, which is consistent with the hypothesis that the Yheb protein is a chitinase.

scholarly journals A wrinkle in flight: the role of elastin fibres in the mechanical behaviour of bat wing membranes

2015 ◽  
Vol 12 (106) ◽  
pp. 20141286 ◽  
Author(s):  
Jorn A. Cheney ◽  
Nicolai Konow ◽  
Andrew Bearnot ◽  
Sharon M. Swartz
Keyword(s):  
Mechanical Behaviour ◽  
High Stress ◽  
Three Dimensional ◽  
Wing Membrane ◽  
Surrounding Matrix ◽  
The Matrix ◽  
Mechanical Element ◽  
Bat Wing ◽  
Surrounding Membrane

Bats fly using a thin wing membrane composed of compliant, anisotropic skin. Wing membrane skin deforms dramatically as bats fly, and its three-dimensional configurations depend, in large part, on the mechanical behaviour of the tissue. Large, macroscopic elastin fibres are an unusual mechanical element found in the skin of bat wings. We characterize the fibre orientation and demonstrate that elastin fibres are responsible for the distinctive wrinkles in the surrounding membrane matrix. Uniaxial mechanical testing of the wing membrane, both parallel and perpendicular to elastin fibres, is used to distinguish the contribution of elastin and the surrounding matrix to the overall membrane mechanical behaviour. We find that the matrix is isotropic within the plane of the membrane and responsible for bearing load at high stress; elastin fibres are responsible for membrane anisotropy and only contribute substantially to load bearing at very low stress. The architecture of elastin fibres provides the extreme extensibility and self-folding/self-packing of the wing membrane skin. We relate these findings to flight with membrane wings and discuss the aeromechanical significance of elastin fibre pre-stress, membrane excess length, and how these parameters may aid bats in resisting gusts and preventing membrane flutter.

Association of Escherichia coli O157:H7 with Filth Flies (Muscidae and Calliphoridae) Captured in Leafy Greens Fields and Experimental Transmission of E. coli O157:H7 to Spinach Leaves by House Flies (Diptera: Muscidae)

2009 ◽  
Vol 72 (7) ◽  
pp. 1547-1552 ◽  
Author(s):  
J. L. TALLEY ◽  
A. C. WAYADANDE ◽  
L. P. WASALA ◽  
A. C. GERRY ◽  
J. FLETCHER ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Fluorescent Protein ◽  
Pcr Amplification ◽  
Escherichia Coli O157 ◽  
Experimental Conditions ◽  
House Flies ◽  
E Coli ◽  
Leafy Greens ◽  
Filth Flies

The recent outbreak of Escherichia coli O157:H7 infection associated with contaminated spinach led to an investigation of the role of insects, which frequent fields of leafy greens and neighboring rangeland habitats, in produce contamination. Four leafy greens fields adjacent to cattle-occupied rangeland habitats were sampled using sweep nets and sticky traps. Agromyzid flies, anthomyiid flies, and leafhoppers were caught consistently in both rangeland and leafy greens production fields at all sites. An unexpected number of flies (n = 34) in the Muscidae and Calliphoridae families (known as filth flies because of their development in animal feces) were caught in one leafy greens field. A subset of these filth flies were positive (11 of 18 flies) for E. coli O157:H7 by PCR amplification using primers for the E. coli O157:H7–specific eae gene. Under laboratory conditions, house flies were confined on manure or agar medium containing E. coli O157:H7 tagged with green fluorescent protein (GFP) and then tested for their capacity to transfer the microbes to spinach plants. GFP-tagged bacteria were detected on surfaces of 50 to 100% of leaves examined by fluorescence microscopy and in 100% of samples tested by PCR. These results indicate that flies are capable of contaminating leafy greens under experimental conditions and confirm the importance of further investigation of the role of insects in contamination of fresh produce.

scholarly journals Mechanotransduction in the Cardiovascular System: From Developmental Origins to Homeostasis and Pathology

Cells ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 1607 ◽  
Author(s):  
Gloria Garoffolo ◽  
Maurizio Pesce
Keyword(s):  
Cardiovascular System ◽  
Mechanical Forces ◽  
Mechanical Stimuli ◽  
Flow Shear ◽  
Surrounding Matrix ◽  
Cellular Mechanotransduction ◽  
Flow Shear Stress ◽  
Sense And Respond ◽  
Metabolic Dysfunctions

With the term ‘mechanotransduction’, it is intended the ability of cells to sense and respond to mechanical forces by activating intracellular signal transduction pathways and the relative phenotypic adaptation. While a known role of mechanical stimuli has been acknowledged for developmental biology processes and morphogenesis in various organs, the response of cells to mechanical cues is now also emerging as a major pathophysiology determinant. Cells of the cardiovascular system are typically exposed to a variety of mechanical stimuli ranging from compression to strain and flow (shear) stress. In addition, these cells can also translate subtle changes in biophysical characteristics of the surrounding matrix, such as the stiffness, into intracellular activation cascades with consequent evolution toward pro-inflammatory/pro-fibrotic phenotypes. Since cellular mechanotransduction has a potential readout on long-lasting modifications of the chromatin, exposure of the cells to mechanically altered environments may have similar persisting consequences to those of metabolic dysfunctions or chronic inflammation. In the present review, we highlight the roles of mechanical forces on the control of cardiovascular formation during embryogenesis, and in the development and pathogenesis of the cardiovascular system.

Role of fabric properties, moisture and friction in transfer of bacteria from fabric to fabric

2019 ◽  
Vol 90 (3-4) ◽  
pp. 478-485 ◽  
Author(s):  
Swati Varshney ◽  
Prashant Pandey ◽  
Deepti Gupta ◽  
Shilpi Sharma
Keyword(s):  
Escherichia Coli ◽  
Acinetobacter Calcoaceticus ◽  
Bacterial Cells ◽  
Healthcare Settings ◽  
Factors Influencing

With increasing reports of textiles serving as vectors for the transmission of infections, it is crucial to study the factors influencing such transfers. This is of concern in various sectors, including healthcare and hospitality, where fabrics constitute an integral part. A better understanding of the fabric types that discourage microbial transfer could help to formulate guidelines for uniforms and other apparels in these sectors. This study aimed to assess the transferability of bacteria from fabrics considering the following factors: fibre and fabric type, moisture and friction. The transfer of bacterial genera important in healthcare settings was quantified with and without application of friction: Escherichia coli and Acinetobacter calcoaceticus from seven different fabrics (cotton, silk, viscose, wool, polyester, polypropylene and a polyester-cotton blend). Amongst the fabrics, transferability was observed to be maximal in polyester followed by viscose, while polypropylene showed the least transfer. Transfer of bacteria was favored by moisture and the application of friction. The study brings forth a correlation between fabric type and the transfer of bacterial cells between fabrics.

Sign in / Sign up

Export Citation Format

Share Document