Using Experimentally Calibrated Regularized Stokeslets to Assess Bacterial Flagellar Motility Near a Surface

The presence of a nearby boundary is likely to be important in the life cycle and evolution of motile flagellate bacteria. This has led many authors to employ numerical simulations to model near-surface bacterial motion and compute hydrodynamic boundary effects. A common choice has been the method o...

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Autores principales:	Orrin Shindell, Hoa Nguyen, Nicholas Coltharp, Frank Healy, Bruce Rodenborn
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	helical flagellum bacterial motility regularized Stokeslets near boundary regularization parameter torque–speed curve Thermodynamics QC310.15-319 Descriptive and experimental mechanics QC120-168.85
Acceso en línea:	https://doaj.org/article/320a20c77b5f47819c85599da59613cf
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id	oai:doaj.org-article:320a20c77b5f47819c85599da59613cf
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spelling	oai:doaj.org-article:320a20c77b5f47819c85599da59613cf2021-11-25T17:31:33ZUsing Experimentally Calibrated Regularized Stokeslets to Assess Bacterial Flagellar Motility Near a Surface10.3390/fluids61103872311-5521https://doaj.org/article/320a20c77b5f47819c85599da59613cf2021-10-01T00:00:00Zhttps://www.mdpi.com/2311-5521/6/11/387https://doaj.org/toc/2311-5521The presence of a nearby boundary is likely to be important in the life cycle and evolution of motile flagellate bacteria. This has led many authors to employ numerical simulations to model near-surface bacterial motion and compute hydrodynamic boundary effects. A common choice has been the method of images for regularized Stokeslets (MIRS); however, the method requires discretization sizes and regularization parameters that are not specified by any theory. To determine appropriate regularization parameters for given discretization choices in MIRS, we conducted dynamically similar macroscopic experiments and fit the simulations to the data. In the experiments, we measured the torque on cylinders and helices of different wavelengths as they rotated in a viscous fluid at various distances to a boundary. We found that differences between experiments and optimized simulations were less than 5% when using surface discretizations for cylinders and centerline discretizations for helices. Having determined optimal regularization parameters, we used MIRS to simulate an idealized free-swimming bacterium constructed of a cylindrical cell body and a helical flagellum moving near a boundary. We assessed the swimming performance of many bacterial morphologies by computing swimming speed, motor rotation rate, Purcell’s propulsive efficiency, energy cost per swimming distance, and a new metabolic energy cost defined to be the energy cost per body mass per swimming distance. All five measures predicted that the optimal flagellar wavelength is eight times the helical radius independently of body size and surface proximity. Although the measures disagreed on the optimal body size, they all predicted that body size is an important factor in the energy cost of bacterial motility near and far from a surface.Orrin ShindellHoa NguyenNicholas ColtharpFrank HealyBruce RodenbornMDPI AGarticlehelical flagellumbacterial motilityregularized Stokesletsnear boundaryregularization parametertorque–speed curveThermodynamicsQC310.15-319Descriptive and experimental mechanicsQC120-168.85ENFluids, Vol 6, Iss 387, p 387 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	helical flagellum bacterial motility regularized Stokeslets near boundary regularization parameter torque–speed curve Thermodynamics QC310.15-319 Descriptive and experimental mechanics QC120-168.85
spellingShingle	helical flagellum bacterial motility regularized Stokeslets near boundary regularization parameter torque–speed curve Thermodynamics QC310.15-319 Descriptive and experimental mechanics QC120-168.85 Orrin Shindell Hoa Nguyen Nicholas Coltharp Frank Healy Bruce Rodenborn Using Experimentally Calibrated Regularized Stokeslets to Assess Bacterial Flagellar Motility Near a Surface
description	The presence of a nearby boundary is likely to be important in the life cycle and evolution of motile flagellate bacteria. This has led many authors to employ numerical simulations to model near-surface bacterial motion and compute hydrodynamic boundary effects. A common choice has been the method of images for regularized Stokeslets (MIRS); however, the method requires discretization sizes and regularization parameters that are not specified by any theory. To determine appropriate regularization parameters for given discretization choices in MIRS, we conducted dynamically similar macroscopic experiments and fit the simulations to the data. In the experiments, we measured the torque on cylinders and helices of different wavelengths as they rotated in a viscous fluid at various distances to a boundary. We found that differences between experiments and optimized simulations were less than 5% when using surface discretizations for cylinders and centerline discretizations for helices. Having determined optimal regularization parameters, we used MIRS to simulate an idealized free-swimming bacterium constructed of a cylindrical cell body and a helical flagellum moving near a boundary. We assessed the swimming performance of many bacterial morphologies by computing swimming speed, motor rotation rate, Purcell’s propulsive efficiency, energy cost per swimming distance, and a new metabolic energy cost defined to be the energy cost per body mass per swimming distance. All five measures predicted that the optimal flagellar wavelength is eight times the helical radius independently of body size and surface proximity. Although the measures disagreed on the optimal body size, they all predicted that body size is an important factor in the energy cost of bacterial motility near and far from a surface.
format	article
author	Orrin Shindell Hoa Nguyen Nicholas Coltharp Frank Healy Bruce Rodenborn
author_facet	Orrin Shindell Hoa Nguyen Nicholas Coltharp Frank Healy Bruce Rodenborn
author_sort	Orrin Shindell
title	Using Experimentally Calibrated Regularized Stokeslets to Assess Bacterial Flagellar Motility Near a Surface
title_short	Using Experimentally Calibrated Regularized Stokeslets to Assess Bacterial Flagellar Motility Near a Surface
title_full	Using Experimentally Calibrated Regularized Stokeslets to Assess Bacterial Flagellar Motility Near a Surface
title_fullStr	Using Experimentally Calibrated Regularized Stokeslets to Assess Bacterial Flagellar Motility Near a Surface
title_full_unstemmed	Using Experimentally Calibrated Regularized Stokeslets to Assess Bacterial Flagellar Motility Near a Surface
title_sort	using experimentally calibrated regularized stokeslets to assess bacterial flagellar motility near a surface
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/320a20c77b5f47819c85599da59613cf
work_keys_str_mv	AT orrinshindell usingexperimentallycalibratedregularizedstokesletstoassessbacterialflagellarmotilitynearasurface AT hoanguyen usingexperimentallycalibratedregularizedstokesletstoassessbacterialflagellarmotilitynearasurface AT nicholascoltharp usingexperimentallycalibratedregularizedstokesletstoassessbacterialflagellarmotilitynearasurface AT frankhealy usingexperimentallycalibratedregularizedstokesletstoassessbacterialflagellarmotilitynearasurface AT brucerodenborn usingexperimentallycalibratedregularizedstokesletstoassessbacterialflagellarmotilitynearasurface
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Using Experimentally Calibrated Regularized Stokeslets to Assess Bacterial Flagellar Motility Near a Surface

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