A novel device for the assessment of shear effects on suspended microbial cultures

Edwards, Nicholas W. M.; Beeton, S.; Bull, Alan T.; Merchuk, José C.

doi:10.1007/bf00264010

Cited by 37 publications

(16 citation statements)

References 15 publications

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“…Few experiments address this subject directly in bacteria, but the results are consistent with these considerations. When grown under high shear force, E. coli elongates without a significant change in its diameter and is more likely to grow in chains (66). Both responses increase the surface area available for attachment while keeping constant the cross-sectional area that is susceptible to shear forces.…”

Section: Shear Forcesmentioning

confidence: 99%

The Selective Value of Bacterial Shape

Young

2006

Microbiol Mol Biol Rev

864

777

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SUMMARY Why do bacteria have shape? Is morphology valuable or just a trivial secondary characteristic? Why should bacteria have one shape instead of another? Three broad considerations suggest that bacterial shapes are not accidental but are biologically important: cells adopt uniform morphologies from among a wide variety of possibilities, some cells modify their shape as conditions demand, and morphology can be tracked through evolutionary lineages. All of these imply that shape is a selectable feature that aids survival. The aim of this review is to spell out the physical, environmental, and biological forces that favor different bacterial morphologies and which, therefore, contribute to natural selection. Specifically, cell shape is driven by eight general considerations: nutrient access, cell division and segregation, attachment to surfaces, passive dispersal, active motility, polar differentiation, the need to escape predators, and the advantages of cellular differentiation. Bacteria respond to these forces by performing a type of calculus, integrating over a number of environmental and behavioral factors to produce a size and shape that are optimal for the circumstances in which they live. Just as we are beginning to answer how bacteria create their shapes, it seems reasonable and essential that we expand our efforts to understand why they do so.

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Section: Shear Forcesmentioning

confidence: 99%

The Selective Value of Bacterial Shape

Young

2006

Microbiol Mol Biol Rev

864

777

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“…Over time, cells are concentrated at the air-water interface by a buoyancy-driven flow; microbe proximity to the atmosphere increases gas exchange rates (Dombrowski et al, 2004;Tuval et al, 2005). Whether suspended in a water droplet, turbulent sea or mammalian blood vessel, cells change naturally in structure (Edwards et al, 1989;Girard and Nerem, 1995;Zirbel et al, 2000), function (Cinamon et al, 2001;McCue et al, 2004) and distribution (over time and in space) due simply to the shear associated with fluid motion.…”

Section: Fluid Motion and Single Cellsmentioning

confidence: 99%

Sex and flow: the consequences of fluid shear for sperm–egg interactions

Riffell

Zimmer

2007

Journal of Experimental Biology

102

124

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SUMMARY Fertilization is a complex interaction among biological traits of gametes and physical properties of the fluid environment. At the scale of fertilization (0.01–1 mm), sperm encounter eggs while being transported within a laminar (or viscous) shear flow. Varying laminar-shear in a Taylor-Couette flow tank, our experiments simulated important aspects of small-scale turbulence within the natural habitats of red abalone(Haliotis rufescens), a large marine mollusk and external fertilizer. Behavioral interactions between individual cells, sperm–egg encounter rates, and fertilization success were quantified, simultaneously, using a custom-built infrared laser and computer-assisted video imaging system. Relative to still water, sperm swam faster and moved towards an egg surface,but only in comparatively slow flows. Encounter rate, swim speed and orientation, and fertilization success each peaked at the lowest shear tested(0.1 s–1), and then decayed as shear increased beyond 1.0 s–1. The decay did not result, however, from damage to either sperm or eggs. Analytical and numerical models were used to estimate the propulsive force generated by sperm swimming (Fswim) and the shear force produced by fluid motion within the vicinity of a rotating egg(Fshear). To first order, male gametes were modeled as prolate spheroids. The ratio Fswim/Fshear was useful in explaining sperm–egg interactions. At low shears where Fswim/Fshear>1, sperm swam towards eggs, encounter rates were pronounced, and fertilization success was very high; behavior overpowered fluid motion. In contrast, sperm swimming,encounter rate and fertilization success all decayed rapidly when Fswim/Fshear<1; fluid motion dominated behavior. The shears maximizing fertilization success in the lab typically characterized natural flow microenvironments of spawning red abalone. Gamete behavior thus emerges as a critical determinant of sexual reproduction in the turbulent sea.

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“…In conditions where the intensity of local turbulence is high but insufficient for the mechanical disruption of the cultivated cells, changes in the cell morphology were often observed [2,56,62,[66][67][68][69][70][71][72][73][74][75][76]. Simultaneously with morphological adjustment, the physiological character, namely, the productivity of metabolite synthesis [66,67,69,72,73,76], biological activity [70,74,77] and enzyme activity [71] also changed.…”

Section: Figmentioning

confidence: 99%

Excess turbulence as a cause of turbohypobiosis in cultivation of microorganisms

2007

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Abstract:The present review describes the influence of different types of mixing systems under excess turbulence conditions on microorganisms. Turbohypobiosis phenomena were described by applying a method for measurement of the kinetic energy of flow fluctuations based on the piezoeffect. It can be assumed that the shear stress effect (the state of turbohypobiosis) plays a role mainly when alternative mechanisms in cells cannot ensure a normal physiological state under stress conditions. Practically any system (inner construction of a bioreactor, culture and cultivation conditions, including mixing) requires its own optimisation to achieve the final goal, namely, the maximum product and/or biomass yields from substrate (Y P/S or/and Y X/S ), respectively. Data on the biotechnological performance of cultivation as well as power input, kinetic energy (e) of flow fluctuations, air consumption rate, rotational speed, tip speed, etc. do not correlate directly if the mixing systems (impellers-baffles) are dissimilar. Even the widely used specific power consumption cannot be relied upon for scaling up the cultivation performance using dissimilar mixing systems. A biochemical explanation for substrate and product transport via cell walls, carbon pathways, energy generation and utilisation, etc. furnishes insight into cellular interactions with turbulence of different origin for different types of microorganisms (single cells, mycelia forming cells, etc.

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A novel device for the assessment of shear effects on suspended microbial cultures

Cited by 37 publications

References 15 publications

The Selective Value of Bacterial Shape

The Selective Value of Bacterial Shape

Sex and flow: the consequences of fluid shear for sperm–egg interactions

Excess turbulence as a cause of turbohypobiosis in cultivation of microorganisms

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