Motility Response to Hydrodynamic Stress During the Growth Cycle in Active Fluid Suspensions

2021 ◽  
Author(s):  
Hadi Fadlallah ◽  
Hassan Peerhossaini ◽  
Christopher T. DeGroot ◽  
Mojtaba Jarrahi
Keyword(s):  
Shear Stress ◽  
Chlamydomonas Reinhardtii ◽  
Growth Process ◽  
Growth Cycle ◽  
Swimming Velocity ◽  
Cellular Motility ◽  
Mechanical Agitation ◽  
Significant Difference ◽  
Hydrodynamic Shear ◽  
Synechocystis Sp

Abstract In this work, we focus on the motility behavior of two model microorganisms widely used in the study of active fluids: Chlamydomonas reinhardtii microalga and Synechocystis sp. cyanobacterium. Understanding the physiological responses of microorganisms under variable environmental conditions is essential for bioreactor engineering. Yet, most of the previous studies focused on the observation of cellular motility regardless of the growth process. Here, we measure the motility of Chlamydomonas reinhardtii and Synechocystis sp. during their growth when subjected to different intensities of hydrodynamic shear stress. The results demonstrate a significant difference in the motility response of the two species against the applied hydrodynamic shear stress. Mechanical agitation appears to affect the motility of Chlamydomonas reinhardtii microalgae by stimulating the growth process and increasing the magnitude of the cellular swimming velocity. This effect is described using an empirical model for the time variation of the motility. Synechocystis cells show a high endurance to the applied shear such that the global effect of agitation intensity on their motility is insignificant. However, it seems that the peak of the swimming velocity always occurs in the middle of exponential phase of growth.

Motility Response to Hydrodynamic Stress During the Growth Cycle in Active Fluid Suspensions

2020 ◽  
Author(s):  
Hadi Fadlallah ◽  
Hassan Peerhossaini ◽  
Christopher De Groot ◽  
Mojtaba Jarrahi
Keyword(s):  
Shear Stress ◽  
Chlamydomonas Reinhardtii ◽  
Growth Process ◽  
Growth Cycle ◽  
Exponential Growth Phase ◽  
Swimming Velocity ◽  
Mechanical Agitation ◽  
Significant Difference ◽  
Hydrodynamic Shear ◽  
Synechocystis Sp

Abstract In this work, we focus on the motility behavior of two model microorganisms widely used in the study of active fluids: Chlamydomonas reinhardtii microalga and Synechocystis sp. Cyanobacterium. Understanding the physiological responses of microorganisms under variable environmental conditions is essential for bioreactor engineering. Yet, most of the previous studies focused on the observation of cellular motility regardless of the growth process. Here, we measure the motility of Chlamydomonas reinhardtii and Synechocystis sp. during their growth when subjected to different intensities of hydrodynamic shear stress. The results demonstrate a significant difference in the motility response of the two species against the applied hydrodynamic shear stress. Mechanical agitation appears to affect the motility of Chlamydomonas reinhardtii microalgae by stimulating the growth process and increasing the magnitude of the cellular swimming velocity. The motility varies following 3 different phases: the rising phase starting almost at the middle of the exponential growth phase, and the decay and damped phases during the stationary phase. This behavior is described using a linear model for the rising phase and a damped oscillatory model for the decay and damped phases. The motility of Synechocystis does not follow a well-defined pattern in time. However, it seems that the peak of the swimming velocity occurs always in the middle of exponential phase of growth. Synechocystis cells show a high endurance to the applied shear such that the global effect of agitation intensity on their motility is insignificant.

Effects of Shear Stress on the Growth Rate of Micro-Organisms in Agitated Reactors

2016 ◽  
Author(s):  
Hadi Fadlallah ◽  
Mojtaba Jarrahi ◽  
Eric Herbert ◽  
Roselyne Ferrari ◽  
Annick Mejean ◽  
...  
Keyword(s):  
Growth Rate ◽  
Shear Stress ◽  
Fluorescent Light ◽  
Light Sources ◽  
Full Time ◽  
Mechanical Agitation ◽  
Closed Chamber ◽  
Initial Dilution ◽  
Hydrodynamic Shear ◽  
Micro Organisms

The effects of hydrodynamic shear stress on the growth rate of cyanobacteria Synechocystis sp. and Chlamydomonas reinhardtii microalgae cells were studied in agitated photobioreactors, since they have different motility rates and sizes. An experimental setup was designed and constructed to monitor the growth rate of the micro-organisms versus the shear rate; experiments were carried out in a well controlled environment, under constant atmospheric pressure and 20 °C temperature. Digitally controlled magnetic agitator-photobioreactors were placed inside a closed chamber with air flow for 4 weeks, under a uniform full-time light intensity provided by two 6-watt white fluorescent light sources. To study the effects of shear stress produced by mechanical agitation on the growth rate of a micro-organism, different agitation frequencies were tested. All reactors were filled with 150 ml of culture medium and micro-organism suspension, with initial dilution factors (mlsuspenion/mltotal volume) of 1/30 and 1/300 for Synechocystis and C. reinhardtii respectively. The vessels were placed on different agitating systems at the desired agitator rotation speed, and were sealed with a cotton membrane from the top in order to permit air exchange with the external environment. The micro-organisms’ growth was monitored daily by measuring the optical density of the suspensions using a spectrophotometer and was then correlated with the cellular concentration, which was measured in turn using a microscopic cell counter. Throughout the experiments pH levels and temperature were measured regularly and adjusted to 7 and 20 °C respectively in order to maintain the photosynthetic activity of the species. In addition, to measure the shear stress inside the agitated reactors, a mathematical model was derived to determine the global shear stress magnitude. To determine the local shear stress distribution, the velocity field in the reactor was measured for different agitation frequencies using PIV. Different zones of high and low shear stress were identified. The results showed that the growth rate is independent of the shear stress magnitude for Synechocystis; Synechocystis showed strong resistance, unlike C. reinhardtii, which showed linear dependence of growth rate and shear stress.

Influence of mixing and shear stress on Chlorella vulgaris, Scenedesmus obliquus, and Chlamydomonas reinhardtii

2012 ◽  
Vol 25 (2) ◽  
pp. 485-495 ◽  
Author(s):  
Marco Leupold ◽  
Stefan Hindersin ◽  
Giselher Gust ◽  
Martin Kerner ◽  
Dieter Hanelt
Keyword(s):  
Shear Stress ◽  
Chlamydomonas Reinhardtii ◽  
Chlorella Vulgaris ◽  
Scenedesmus Obliquus

scholarly journals Characterization of Chlamydomonas reinhardtii phosphatidylglycerophosphate synthase in Synechocystis sp. PCC 6803

2015 ◽  
Vol 6 ◽  
Author(s):  
Chun-Hsien Hung ◽  
Kaichiro Endo ◽  
Koichi Kobayashi ◽  
Yuki Nakamura ◽  
Hajime Wada
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Synechocystis Sp ◽  
Pcc 6803

The functional allometry of semicircular canals, fins, and body dimensions in the juvenile centrarchid fish, Lepomis gibbosus (L.)

Development ◽  
1973 ◽  
Vol 29 (3) ◽  
pp. 721-743
Author(s):  
Howard C. Howland ◽  
Joseph Masci
Keyword(s):  
Body Mass ◽  
Semicircular Canal ◽  
Semicircular Canals ◽  
Lepomis Gibbosus ◽  
Swimming Velocity ◽  
Body Dimensions ◽  
Moments Of Inertia ◽  
Significant Difference ◽  
Vertical Semicircular Canal ◽  
Vertical Semicircular Canals

1. The ontogenetic allometry of radii of curvature and the tube radii of the semicircular canals of approximately 85 juvenile (2–20 g) centrarchids of the species Lepomis gibbosus (L.) was investigated. The radii of curvature of the semicircular canals have different allometries; these arefor the anterior vertical, posterior vertical and horizontal canals respectively. The differences in growth exponents between the anterior and posterior vertical semicircular canals and between the anterior vertical and horizontal semicircular canals were statistically significant (P < 0·02 and P < 0·05 respectively). 2. Body mass and standard length were almost equally good predictors of the radii of curvature of the anterior vertical semicircular canals, but body mass was the better predictor of the radii of curvature of the posterior vertical and horizontal semicircular canals, as judged by the magnitude of the mean squares about the logarithmic regressions of radii on length and mass. 3. By measuring and estimating the area moments of the fins of the fish, the moments of inertia about various axes and the allometry of the characteristic swimming velocity of the fish, we attempted to account for the magnitude and direction of the differences in allometric growth exponents of the radii of curvature of the semicircular canals. Unexplained by our best estimate of growth exponents was the very high value observed for the posterior vertical semicircular canals. 4. No significant correlation could be found between the residuals of the major dimensions of the posterior vertical semicircular canals and those of body width or depth once the influence of body mass was removed. This finding suggests the rejection of the hypothesis that the allometry of this semicircular canal is simply correlated with overall body expansion in its plane. 5. The discrepancies between our predictions and observations of growth exponents could be explained by a gradual increase of the spring constant of the semicircular canals on the order ofthough they may also be due to other factors neglected in our model, e.g. the allometry of the added mass of the fish. 6. No evidence suggested that the shape of the semicircular canals was altered over the size range of the fish we studied. However, among the fins of the fish and the major body dimensions, only the width and the depth of the fish exhibited growth constants that did not differ significantly from each other. 7. We computed the effective toroidal radii of the non-toroidal-shaped vertical semicircular canals and found that the equivalent toroidal radius of the anterior vertical semicircular canal was consistently greater than that of the posterior vertical semicircular canal. This difference is explicable on the basis of the different moments of inertia of the animal about axes through the center of gravity and parallel to the axes of the semicircular canals. 8. We computed the allometry of the ratios R̄/r2 for all three semicircular canals and found in accordance with the prediction of Jones & Spells that they did not differ significantly from zero. 9. The allometry of the outer tube radii of the several semicircular canals was determined, and, while there was no significant difference in the growth exponents of the tube radii, it was noted that the tube radius of the horizontal semicircular canal was consistently and significantly smaller than that of the vertical semicircular canal. We suggested that this difference might be due to the broader range of frequencies that the fish experienced about its yaw axis. 10. Taken as a whole the data and calculations of this paper generally support the theory that the dimensions of the semicircular canals and the ontogenetic changes in them attune the semicircular canals to the angular frequency spectra that the fish experience about their axes.

scholarly journals A Bayesian approach to modelling the impact of hydrodynamic shear stress on biofilm deformation

PLoS ONE ◽  
2018 ◽  
Vol 13 (4) ◽  
pp. e0195484 ◽  
Author(s):  
Oluwole K. Oyebamiji ◽  
Darren J. Wilkinson ◽  
Pahala Gedara Jayathilake ◽  
Steve P. Rushton ◽  
Ben Bridgens ◽  
...  
Keyword(s):  
Shear Stress ◽  
Bayesian Approach ◽  
Hydrodynamic Shear ◽  
The Impact

Effect of shear stress upon localization of the Golgi apparatus and microtubule organizing center in isolated cultured endothelial cells

1993 ◽  
Vol 104 (4) ◽  
pp. 1145-1153 ◽  
Author(s):  
D.E. Coan ◽  
A.R. Wechezak ◽  
R.F. Viggers ◽  
L.R. Sauvage
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Cell Migration ◽  
Golgi Apparatus ◽  
Flow Direction ◽  
Microtubule Organizing Center ◽  
Directed Cell Migration ◽  
Time Period ◽  
Significant Difference ◽  
Organizing Center

Despite substantial evidence to suggest that directed cell migration is dependent upon positioning of the Golgi apparatus (GA) and the microtubule organizing center (MTOC), some controversy exists about whether such a relationship is relevant to endothelial cells under flow. The present study was undertaken to provide an indepth investigation of the relationship between shear stress, GA/MTOC localization, cell migration and nuclear position. Bovine carotid endothelial cells were exposed to 22 or 88 dynes/cm2 for 0.5, 2, 8 or 24 h, and localization of their GA/MTOCs was determined relative to the direction of flow. In no-flow control specimens, (0, 0.5, 2, 8 and 24 h) there was no change in the equally distributed GA/MTOCs. In contrast, during the first 8 h at 88 dynes/cm2 and by 2 h at 22 dynes/cm2 there was a significant increase in the number of cells with GA/MTOCs localized upstream to flow direction. The effect was temporary, however, and by 24 h there was no significant difference between the no-flow, 22 and 88 dynes/cm2 specimens. Analysis of GA/MTOC localization with respect to the direction of cell migration determined that 72.5% of no-flow cells possessed GA/MTOCs localized to the sides of nuclei nearest the direction of migration. In contrast, 64% of the specimens shear stressed over the same time period had GA/MTOCs localized to the sides of nuclei opposite the direction of migration. These results suggest that positioning of the GA/MTOC in endothelial cells is not dependent completely upon the direction of migration.(ABSTRACT TRUNCATED AT 250 WORDS)

In Vitro Imaging Technique of Cell Adhesion

2002 ◽  
Author(s):  
Chen Dong
Keyword(s):  
Shear Stress ◽  
Cell Adhesion ◽  
Shear Flow ◽  
Imaging Technique ◽  
Contact Length ◽  
Adherent Cell ◽  
Side View ◽  
Cell Deformability ◽  
Hydrodynamic Shear

It is the first object of this article to contribute a side-view imaging technique to investigate adhesion to a surface-immobilized ICAM-1 in shear flow, wherein T-leukemic Jurket cells have been used. A side view image has revealed that the cell adhesion on ICAM-1 under flow conditions in vitro is quasistratic. Changes in flow shear stress, cell deformability, or substrate ligand strength resulted in a significant change in the characteristic adhesion binding time and contact length. The elongation of cells in shear flow tempers hydrodynamic shear forces on the cell, which affects the transients in cell-surface adhesion. It is the second object to calculate a 3-D flow field with shear stress acting on an adherent cell based on the shape of the cell obtained from the image. The application of the side-view imaging technique and the image analysis may provide a practical assay to reveal fundamental behavior of a cell.

Bacterial survival and biofilm formation on conventional and antibacterial toothbrushes

Biofilms ◽  
2004 ◽  
Vol 1 (2) ◽  
pp. 123-130 ◽  
Author(s):  
R. L. Sammons ◽  
D. Kaur ◽  
P. Neal
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Staphylococcus Epidermidis ◽  
Biofilm Formation ◽  
Bacterial Survival ◽  
Opportunistic Pathogens ◽  
Mechanical Agitation ◽  
Gram Staining ◽  
Colony Forming Units ◽  
Significant Difference ◽  
Number Of Bacteria

The aim of this study was to investigate bacterial survival and biofilm formation on toothbrushes. Fifteen healthy volunteers each used a normal toothbrush and an antibacterial toothbrush of the same design for two separate 5 week periods. Bacteria were removed from the brush head by swabbing and mechanical agitation in 10ml of tryptone soya broth, cultured aerobically on selective and non-selective media, and classified by Gram staining, catalase and oxidase tests. Survival of Staphylococcus epidermidis and Pseudomonas aeruginosa was monitored in the laboratory on both types of brush over 8 days. Scanning electron microscopy was used to observe biofilm formation on antibacterial and conventional brushes used for various times. Numbers of bacteria isolated from conventional and antibacterial brushes from different individuals ranged from 8.3×103 to 4.7×106 and from 1×102 to 1.2×106 colony-forming units/ml, respectively. A larger number of bacteria were isolated from conventional brushes than from antibacterial brushes used by the same individuals but no statistically significant difference was demonstrated. No differences in the relative proportions of Gram-negative and Gram-positive rods or cocci were seen. Staphylococci, presumptive coliforms and pseudomonads were isolated from 48%, 28% and 16% of brushes, respectively. Pseudomonas aeruginosa was viable for at least 4 days on conventional, and 2–3 days on antibacterial, brushes, whilst S. epidermidis survived for 6–8 days on antibacterial and more than 8 days on conventional brushes. Biofilms formed on the heads and bristles of both conventional and antibacterial brushes. Extensive, mixed community biofilms developed after several months of use. We conclude that toothbrushes may be a reservoir of opportunistic pathogens including staphylococci and pseudomonad-like organisms and must be considered as a potential source of haematogenous infections and cross-infection.

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